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TURBINE ROTOR MATERIAL DESIGN PROGRAM

TASK 2

EFFECT OF FORGING ON HARD ALPHA MORPHOLOGY

Deformation Strain Needed to Crack Hard Alpha Anomalies

Prepared By

Shesh Srivatsa

GE Aircraft Engines

Cincinnati, OH [email protected]

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TABLE OF CONTENTS

LIST OF FIGURES ..................................................................................................................... iii

LIST OF TABLES ....................................................................................................................... ix

SUMMARY................................................................................................................................... x

1.0 INTRODUCTION ............................................................................................................... 1

1.1 Hard Alpha Anomaly Micro-Modeling....................................................................... 1

1.2 Summary of Previous Work ........................................................................................ 2

1.3 Microcode Parametric Study....................................................................................... 2

2.0 DEFORMATION STRAIN NEEDED TO CRACK HARD ALPHA............................ 4

2.1 Objective ...................................................................................................................... 4

2.2 Significance of this Task ............................................................................................. 4

2.3 Summary of Accomplishments.................................................................................... 4

3.0 WORK ITEM 1: STRAIN TO CRACK HARD ALPHA............................................... 5

3.1 Objective ...................................................................................................................... 5

3.2 Accomplishments ........................................................................................................ 5

3.3 Constitutive Equations For Hard Alpha ...................................................................... 6

3.4 Definitions of Hard Alpha and Diffusion Zone ........................................................... 7

3.5 Strain to Cracking and Damage Results ...................................................................... 8

3 6 U f St i t C ki d D C t Pl t 15

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5.3 Ingot to Billet Conversion Damage ........................................................................... 32

5.4 Application of Damage and Cracking Strain to Forged Disks.................................. 33

5.5 Strain to Cracking Conclusions ................................................................................. 37

6.0 WORK ITEM 4: ANOMALY ORIENTATION ........................................................... 38

6.1 Objective .................................................................................................................... 38

6.2 Accomplishments ...................................................................................................... 38

6.3 Results........................................................................................................................ 38

7.0 SUMMARY AND CONCLUSIONS................................................................................ 45

8.0 ACKNOWLEDGEMENTS .............................................................................................. 47

9.0 REFERENCES .................................................................................................................. 47

10.0 APPENDIX 1: STATEMENT OF WORK DATED APRIL 9, 2003........................... 48

10.1 Significance of this Task ........................................................................................... 48

10.2 Work to be performed................................................................................................ 48

11.0 APPENDIX 2: STRAIN TO CRACKING PLOTS ....................................................... 50

12.0 APPENDIX 3: HARD ALPHA DAMAGE PLOTS ...................................................... 83

13.0 APPENDIX 4: Ti-64 AND HARD ALPHA FLOW STRESS PLOTS ...................... 116

14.0 APPENDIX 5: DAMAGE, STRAIN, STRAIN RATE, AND TEMPERATURE

CONTOURS PLOTS FOR SEEDED FORGINGS SB1 SB4................................... 123

15 0 APPENDIX 6: DAMAGE STRAIN STRAIN RATE AND TEMPERATURE

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LIST OF FIGURES

Figure 1. Definition of microvolume consisting of the anomaly surrounded by adiffusion zone, and then by the parent material. Initial and deformed shapesof the microvolume are schematically shown here. ................................................... 1

Figure 2. Contours of strain to cracking as a function of strain rate and temperature. ............. 11

Figure 3. Contours of strain to cracking as a function of temperature and damage.................. 12

Figure 4. Contours of hard alpha damage as a function of strain rate and temperature. ........... 13

Figure 5. Contours of hard alpha damage as a function of temperature and macrostrain. ........................................................................................................................ 14

Figure 6. Description of how to use damage results. ................................................................ 16

Figure 7. Description of how to use strain to cracking results. ................................................. 17

Figure 8. Damage in SB1 SB3. .............................................................................................. 23

Figure 9. Damage in SB4. ......................................................................................................... 24

Figure 10. Seed locations in forging SB1................................................................................. 25

Figure 11. SB1 Seeds: Comparison of predicted damage with extent of cracking. .................. 26

Figure 12. Seed locations in forging SB3................................................................................. 27

Figure 13. SB3 Seeds: Comparison of predicted damage with extent of cracking. .................. 28

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Figure 22. Graphical display of overall deformation and orientation in forgings SB1 -SB4. .......................................................................................................................... 40

Figure 23. Flowlines - AE 2100/3007 Stage 14 compressor disk. ............................................ 41

Figure 24. Graphical display of overall deformation and orientation in AE 2100/3007Stage 14 compressor disk. ........................................................................................ 42

Figure 25. Flowlines - AE 3007 Fan disk.................................................................................. 43

Figure 26. Graphical display of overall deformation and orientation in AE 3007 Fan

disk. .......................................................................................................................... 44

Figure 27. Contours of strain to cracking as a function of strain rate and temperature. ........... 51




Figure 31. Contours of strain to cracking as a function of temperature and damage................ 55

Figure 32. Contours of strain to cracking as a function of temperature and damage................ 56

Figure 33. Contours of strain to cracking as a function of strain rate and damage................... 57

Figure 34. Contours of strain to cracking as a function of strain rate and damage................... 58

Figure 35. Contours of strain to cracking as a function of HA N2 and temperature................. 59

Figure 36. Contours of strain to cracking as a function of HA N2 and temperature................. 60

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Figure 47. Contours of strain to cracking as a function of DZ N2 and temperature. ................ 71

Figure 48. Contours of strain to cracking as a function of DZ N2 and temperature. ................ 72

Figure 49. Contours of strain to cracking as a function of DZ N2 and strain rate. ................... 73




Figure 53. Contours of strain to cracking as a function of DZ N2 and damage........................ 77

Figure 54. Contours of strain to cracking as a function of DZ N2 and damage........................ 78

Figure 55. Contours of strain to cracking as a function of HA N2 and DZ N2. ....................... 79




Figure 59. Contours of hard alpha damage as a function of strain rate and temperature.......... 84

Figure 60. Contours of hard alpha damage as a function of strain rate and temperature. ......... 85



Fi 63 C f h d l h d f i f d

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Figure 71. Contours of hard alpha damage as a function of HA N2 and strain rate. ................ 96




Figure 75. Contours of hard alpha damage as a function of HA N2 and macro strain. .......... 100

Figure 76. Contours of hard alpha damage as a function of HA N2 and macro strain. .......... 101

Figure 77. Contours of hard alpha damage as a function of DZ N2 and temperature............. 102




Figure 81. Contours of hard alpha damage as a function of DZ N2 and strain rate................ 106

Figure 82. Contours of hard alpha damage as a function of DZ N2 and strain rate. ............... 107



Figure 85. Contours of hard alpha damage as a function of DZ N2 and macro strain. ........... 110

Figure 86. Contours of hard alpha damage as a function of DZ N2 and macro strain. ........... 111

Fi 87 C f h d l h d f i f HA N2 d DZ N2 112

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Figure 97. Seeded Forgings (SB1 - SB4) - 1........................................................................... 124



Figure 100. Seeded Forgings (SB1 - SB4) - 4......................................................................... 127






Figure 106. Seeded Forgings (SB1 - SB4) - 10....................................................................... 133

Figure 107. RR P/N 68014, AE 2100/3007 Stage 14 compressor disk - 1. ............................ 135






Fi 113 RR P/N 68014 AE 2100/3007 S 14 di k 7 141

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Figure 123. RR P/N 68696, AE3007 Fan disk - 6................................................................... 152




Figure 127. RR P/N 68696, AE3007 Fan disk - 10................................................................. 156




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LIST OF TABLES

Table 1. Results of parametric study summarizing the influence of variousindependent variables on the deformation of the diffusion zone and the

hard alpha. .................................................................................................................. 3

Table 2. Variables used in strain to cracking study. .................................................................... 8

Table 3. Details of seeds in forgings SB1 SB4. ..................................................................... 22

Table 4. Damage during ingot to billet conversion. ................................................................ 161

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SUMMARY

In order to realistically assess the effects of forming processes on the hard alpha anomaly distribution, an

accurate model of the anomaly deformation behavior is needed. Since the anomaly is much smaller insize than a forging, a two-step procedure was adopted. First, the forging process was simulated(macrocode) assuming that the anomaly has no effect on the bulk material flow. Second, a small regionaround the anomaly was modeled (microcode) with the deformation boundary conditions from the macrosimulation. This strategy permits realistic modeling of anomaly deformation with little added complexity.

In Phase I and earlier in Phase II of the TRMD (Turbine Rotor Material Design) program, a microcodewas developed and validated to predict the size and orientation of hard alpha anomalies. DOE (Design OfExperiments) based models were used to correlate anomaly deformation and forging macro strain. This

correlation predicts anomaly deformation quickly and accurately for both billet conversion andcomponent forging and can be used to modify the hard alpha anomaly distribution used in lifing analyses.

As a follow-on, another activity was defined with the objective of determining the deformation macrostrain required to crack hard alpha anomalies in order to determine the likelihood of non-cracked hardalpha under typical forming conditions. In this study, hard alpha is defined as the region with nitrogencontents greater than 4% and diffusion zone as the region with nitrogen contents less than 4%. The hardalpha exhibits brittle fracture where as the diffusion zone has good ductility. Each is described by its own

constitutive equations. The results of the strain to cracking study are reported here. These results maydirect the future development of NDE UT (Non-Destructive Evaluation Ultra-sonic) methods and/orchanges to current inspection procedures to enhance anomaly detectability.

Hard alpha cracking strain and damage (extent of cracking) were determined as functions of nitrogencontent and deformation parameters. The model was validated with the limited seeded billet experimentaldata from TRMD Phase II. Hard alpha cracking strain increases and damage decreases with decreasinganomaly nitrogen content, increasing temperature, and decreasing strain rate. Damage and forging flowlines along which anomalies tend to orient were computed for three generic Ti-64 forging shapes as

examples. When flow lines are normal to a face, a scan from another face, or a shear scan should be usedto enhance anomaly detectability. These three cases are examples, and in general, the results for anyforging should be evaluated on a case-by-case basis.

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1.0 INTRODUCTION

1.1 Hard Alpha Anomaly Micro-Modeling

In order to make realistic assessments of the effects of forging on the anomaly distribution, an

accurate model is needed to describe the deformation of the brittle hard alpha anomalies.Realistic modeling of these anomalies is difficult due to the complex mechanical behavior of the

material, as well as the large deformations they can encounter during thermo-mechanicalprocessing, such as ingot to billet conversion, extrusion, or component forging. Further, the largedisparity in length scales between the anomaly and the component forging makes it impractical

to model the anomaly and the component simultaneously.

Typical aircraft engine disk forging sizes are in the range of 6 to 30 (15 cm to 75 cm) indiameter and typical hard alpha anomaly sizes of concern are about 0.10 (2.5 mm) in size orsmaller. Due to this extreme size ratio between the full-scale part and the anomaly, a two-step

macro-micro level simulation was adopted. First, the entire forging process was simulated(macro level) using material properties for the titanium alloy and assuming that the presence of

the anomaly had no effect on the bulk flow behavior of the material. Second, a small regionaround the anomaly was identified, the geometry and key material properties of the anomaly

were defined, and a small volume of the matrix material with the nitrogen diffusion zone andhard alpha anomaly was forced through the same deformation pattern as the original material(micro level simulation).

In the micro model, the deformation of a volume, referred to as a micro-volume, is simulated.The micro-volume (Figure 1) consists of the anomaly surrounded by a diffusion zone, and then

by the parent material. The boundaries of the micro-volume extend well beyond that of theanomaly. Beyond the boundaries of the micro-volume, the presence of the anomaly is assumed to

have a negligible effect on the deformation in the parent material. This is true unless the anomalysize is comparable to the local forging size. The advantage of this approach is that it de-couplesthe deformation of the anomaly and the parent material, allowing each calculation to be

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1.2 Summary of Previous Work

Previous work conducted during the TRMD Phase I program and earlier during Phase II is

summarized below.

Developed and validated the microcode to predict the overall size and orientation of hardalpha anomalies ignoring voiding/cracking.

Conducted seeded billet forging experiments to obtain data to validate the macro andmicro codes.

28 of the 44 seeds from the seeded forgings were cut up for microcode validation.

Compared measured and predicted anomaly deformation: Good agreement between measurements and predictions: better for the diffusion

zone than for the hard alpha deformation.

Developed relationships between anomaly deformation and forging macro strain. Regression equations can be used with both DEFORM

TM3-D or 2-D.

Regression equations can be used for both billet conversion and componentforging. Predict anomaly deformation quickly and accurately via regression equations.

Modify the anomaly distribution used in lifing analysis.

Proposed methodology to apply anomaly deformation information. Forging macro strain components in 3 directions available from DEFORM

TM.

Scale to hard alpha and diffusion zone strain components using regression

equations. Modify the anomaly distribution used in lifing analysis.

Enables the microcode output to be input into DARWIN simply but accurately.

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Not significant DZ to HA size ratio Inclusion aspect ratio Hydrostatic pressure

Hard alpha more brittle at lower temperatureHA deformation decreaseswith increasingtemperature

Forging temperature

Hard alpha more brittle at higher strain rateHA deformation increaseswith increasing strain rate

Forging strain rate

Dependence on diffusion zone nitrogen content ismoderate

Diffusion zone flow stress increases with itsnitrogen content

HA deformation increases

with increasing DZ N2

Diffusion Zone N2 Content

Dependence on hard alpha nitrogen content ismoderate to low

Hard alpha flow stress is about 25% higher at 8%than at 4% N2

HA deformation decreases

with increasing HA N2

Hard Alpha N2 Content

CommentEffectVariable

Not significant DZ to HA size ratio Inclusion aspect ratio Hydrostatic pressure

Hard alpha more brittle at lower temperatureHA deformation decreaseswith increasingtemperature

Forging temperature

Hard alpha more brittle at higher strain rateHA deformation increaseswith increasing strain rate

Forging strain rate

Dependence on diffusion zone nitrogen content ismoderate

Diffusion zone flow stress increases with itsnitrogen content

HA deformation increases

with increasing DZ N2

Diffusion Zone N2 Content

Dependence on hard alpha nitrogen content ismoderate to low

Hard alpha flow stress is about 25% higher at 8%than at 4% N2

HA deformation decreases

with increasing HA N2

Hard Alpha N2 Content

CommentEffectVariable

Table 1. Results of parametric study summarizing the influence of various independent variables on the deformation

of the diffusion zone and the hard alpha.

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2.0 DEFORMATION STRAIN NEEDED TO CRACK HARD ALPHA

2.1 Objective

Determine the deformation macro strain required to crack hard alpha anomalies.

2.2 Significance of this Task

Provide insight into likelihood of non-cracked hard alpha under typical billet conversionand forging conditions.

Provide insight into typical orientations of hard alpha in forgings.

Results may direct future development of inspection procedures to enhance detectabilityof hard alpha anomalies.

2.3 Summary of Accomplishments

The strain to hard alpha cracking study was completed and validated with limited experimentaldata. This study consisted of four work items:

Work Item 1 Strain to Crack Hard Alpha

Determined HA cracking strain and damage (extent of cracking) as function of: Nitrogen content; Deformation parameters.

Work Item 2 Cracking Strain vs Deformation Strain

Evaluated HA cracking strain relative to strain during component forging. Extent of cracking represented by damage.

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3.0 WORK ITEM 1: STRAIN TO CRACK HARD ALPHA

3.1 Objective

Determine the relationship between hard alpha nitrogen content and strain to hard alpha cracking

using TRMD data and the micro- and macro-codes. The strain to hard alpha cracking is afunction of the variables: hard alpha nitrogen content, diffusion zone nitrogen content,

deformation temperature and strain rate. The results will be presented as contours of strain tohard alpha cracking as a function of two variables, with the other variables held constant.

3.2 Accomplishments

The microcode developed in TRMD Phase I was based on the UNIX version ofDEFORM

TM. With the move towards PC based platforms, the microcode was transitioned

from Unix to Windows-2000 based computers using the PC version of DEFORMTM

. Theuser interface with this version is totally different from the unix version. Tests were

conducted to ensure that the microcode features work properly and that the PC versionreproduces the Unix results for standard runs. Some minor inconsistencies associated withfortran 90 vs fortran 77 were fixed.

A web based fortran compilation procedure was created at SFTC (Scientific Forming

Technologies Corporation licensors of DEFORMTM

to compile user subroutines. Thispermits users to compile their user subroutines on the internet. Two procedures weresetup: one for the compilation of subroutines associated with the finite element simulation

and the other for subroutines associated with post-processing. Both procedures were tested

and they worked satisfactorily.

Strain to hard alpha cracking was determined as a function of: Hard alpha nitrogen content,

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3.3 Constitutive Equations For Hard Alpha

Constitutive equations for hard alpha were developed in TRMD Phase I. These data were used

here to obtain the damage and strain to crack hard alpha. Complete details of the constitutiveequations and the experimental testing are provided in Reference 3. A brief summary is

provided below.

The flow and fracture behavior of hard alpha was studied as a function of nitrogen content, stressstate, strain, strain rate, and temperature. Hard-alpha specimens with nitrogen contents rangingfrom 2 to 11.6 weight per cent were fabricated. Stress-strain curves were obtained under various

states of stress by performing uniaxial compression, indirect tension, indentation, and plane-

strain compression tests at two strain rates. The yield strength increases with increasing nitrogencontent and with increasing strain rate, but decreases with increasing temperature. Hard alphaundergoes substantial plastic deformation for nitrogen contents less than 4%, but it exhibitsbrittle fracture with little plastic flow for nitrogen contents 5.5% and higher.

In TRMD Phase I, constitutive equations describing the onset and evolution of the failure

of hard alpha were developed. The constitutive equations developed describe the fracture ofhard alpha (intact material) and the failure stress of damaged hard alpha as a function of damage

using a continuum damage mechanics formulation. The equations are briefly described below.More details are provided in Reference 3.

For intact material, the flow or fracture stress, Yi, of hard alpha is given by:

+=

n

ni

Y

PlogZXYY

( 1)

whereX= 1.4,

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whereD is an internal variable representing the state of damage. The value ofD is zero for intactmaterial and it is 1 when the material fails completely.

The damage rate is given by:

= && 3cD

where & is the strain rate

( ) N.%wtNfore.c Nc. 417518 4151603 = &

c4 = -0.0964 (wt.% N-1) and N is nitrogen content in wt.%. ( 5)

The accumulated damage at any time is obtained by integrating the damage rate equation:

== dtcdtDD && 3 ( 6)

3.4 Definitions of Hard Alpha and Diffusion Zone

The constitutive property data generated experimentally in TRMD Phase I (Reference 1) indicate

that hard alpha deforms plastically when the nitrogen content is less than 4 weight %, butfractures when the nitrogen content is 4 weight % or greater. Guided by these experimental

observations, constitutive equations were developed to describe the fracture behavior of hardalpha with high nitrogen contents ( > 4 % N) and the plastic flow behavior of hard alpha with

low nitrogen contents ( < 4 % N).

Henceforth, the region with nitrogen content greater than 4% is called a hard alpha and the

region with nitrogen content less than 4% is called a diffusion zone Each is described by its own

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3.5 Strain to Cracking and Damage Results

The hard alpha constitutive and damage equations describ ed in the previous section were used to

determine the strain to hard alpha cracking and damage. Table 2 lists the values of the variablesused. Diffusion zone was defined as 1 to 4% nitrogen content; at these nit rogen contents, the

anomaly shows good ductility and no cracking. Hard alpha was defined as greater than 4%nitrogen content; at these nitrogen contents, the anomaly exhibits poor ductility and cracking.

Calculations were done upto 8% hard alpha nitrogen content, since there is little difference forhigher nitrogen contents.

VARIABLE Min/Max Levels

Hard Alpha N2 content (weight %) 4, 8

Diffusion Zone N2 content (weight %) 1, 3

Strain rate (1/sec) 0.1, 1.0

Temperature (F) 1550, 1750

Macro forging strain 0.1, 2.1

Damage 0, 1

Table 2. Variables used in strain to cracking study.

The calculation steps are summarized below:

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3. The forging macro strains to reach several values of damage in the range of 0 to 1 werecalculated. Hard alpha cracking starts when the damage exceeds zero. For a damage

value of unity, the hard alpha is fully cracked. Cracking occurs over a range of damage

and macro strain. Therefore, cracking was defined to have occurred if the hard alphadamage (from equation (6)) reached a pre-defined damage value. If the damage

calculated in step 3 exceeded the pre-defined critical damage, cracking was deemed tohave occurred. The corresponding forging strain to reach the extent of cracking defined

by this value of damage was calculated. This strain, as a function of hard alpha N2content, diffusion zone N2 content, strain rate, temperature, and critical damage, wassaved for use in the DEFORMTM user subroutine. The use in the subroutine was again

through a table look up function similar to that described for damage in step 2.

Strain to hard alpha cracking was obtained as a function of five variables: Hard alpha nitrogen content, Diffusion zone nitrogen content,

Deformation temperature, Deformation strain rate, and

Critical damage indicating the extent of cracking.

Hard alpha damage was obtained as a function of five variables: Hard alpha nitrogen content, Diffusion zone nitrogen content,

Deformation temperature, Deformation strain rate, and Macro strain.

Since the microcode does not explicitly predict cracking, damage was used to indicate the extent

of cracking. Strain to cracking, strain rate and temperature all refer to macro forging values.

The results were plotted in various ways for ease of use and interpretation. There are a total of 5

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and the associated reduction in flow stress dominates thermal softening. At higher macro strains,when damage has occurred at all temperatures, the flow stress shows the normal decrease with

increasing temperature. At high macro strains, the thermal softening dominates as damage has

occurred at all temperatures.

At higher strain rate, hard alpha deforms less since the ratio of the flow stress of HA to base Ti-64 increases with strain rate. Damage is proportional to both strain rate and to strain.

This shows that depending on the deformation region (strain, strain rate, temperature), the trendsin flow stress can be quite different. For this reason, the strain to cracking and damage do not

vary monotonically with some of the deformation parameters.

To summarize, the strain to hard alpha cracking increases and damage decreases with decreasing hard alpha nitrogen content, decreasing diffusion zone nitrogen content,

increasing temperature, and decreasing strain rate.

In other words more forging macro strain is needed to crack an anomaly with a lower hard alpha

nitrogen content or a lower diffusion zone nitrogen content or at a higher temperature or at alower strain rate.

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Figure 2. Contours of strain to cracking as a function of strain rate and temperature.

Strain to Cracking decreases with increasing DZ N2 % (compare left/right figures).

Strain to Cracking decreases with increasing HA N2 % (compare top/bottom figures).

Strain to Cracking decreases with increasing strain rate and with decreasing temperature.

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Figure 3. Contours of strain to cracking as a function of temperature and damage.

Strain to Cracking decreases with increasing strain rate (compare left/right figures).

Strain to Cracking decreases with increasing DZ N2 % (compare top/bottom figures).

Strain to Cracking decreases with decreasing temperature and with decreasing critical damage.

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Figure 4. Contours of hard alpha damage as a function of strain rate and temperature.

Damage increases with increasing DZ N2 % (compare left/right figures).

Damage increases with increasing HA N2 % (compare top/bottom figures).

Damage increases with increasing strain rate and with decreasing temperature.

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Figure 5. Contours of hard alpha damage as a function of temperature and macro strain.

Damage increases with increasing strain rate (compare left/right figures).

Damage increases with increasing DZ N2 % (compare top/bottom figures).

Damage increases with decreasing temperature and with increasing macro strain.

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3.6 Use of Strain to Cracking and Damage Contour Plots

The use of the damage and the strain to cracking plots is described below and shown in Figure 6 and

Figure 7.

The way to use these plots, is to first find the plot with the most suitable contour axes; e.g., if strainrate and temperature are known and results are desired for several HA N2 and DZ N2, a plot with the

latter two as the contour axes should be selected. The deformation conditions of macro strain, strainrate and temperature are located at the given HA N2 % and DZ N2% and this gives the damagevalue. Damage equal to zero indicates an intact hard alpha anomaly. Damage equal to 1 indicates a

fully failed hard alpha anomaly. Therefore, the larger the damage value, the more extensive the

cracking of the hard alpha anomaly.

The strain to cracking plots should be used in the same way. First the plot with the most suitablecontour axes is selected. The point at the given values of the 5 variables is located to obtain the

cracking strain contour value. The cracking strain is compared with the macro strain from a forgingmodel of the deformation process. This determines if a hard alpha anomaly at the location will crack

and the corresponding damage value indicates the extent of cracking.

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Figure 6. Description of how to use damage results.

With HA N2 at 8%, DZ N2 at 3%, strain rate at 0.5/sec, temperature at 1650F, a macro strain of 0.3 would result in a damage of 0.42.

Damage = 0 (no cracking), Damage = 1 (fully cracked).

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Figure 7. Description of how to use strain to cracking results.

With HA N2 at 4%, DZ N2 at 1%, strain rate at 0.5/sec, temperature at 1650F, a macro strain of 1.25 would result in a damage of 0.5.

Damage = 0 (no cracking), Damage = 1 (fully cracked).

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3.7 List of Hard Alpha Cracking Strain Contour Plots

A few select plots were shown in Figure 2 thru Figure 7. The cracking strain was plotted as contours

in two variables, holding the other three variables at specified values. The results were plotted invarious ways for ease of use and interpretation. All the strain to cracking plots are included in

APPENDIX 2: STRAIN TO CRACKING PLOTS.

List of plots:

Cracking Strain - f(Strain Rate, Temperature), given HA N2, DZ N2, Damage Cracking Strain - f(Temperature, Damage), given HA N2, DZ N2, Strain Rate

Cracking Strain - f(Strain Rate, Damage), given HA N2, DZ N2, Temperature Cracking Strain - f(HA N2, Temperature), given DZ N2, Strain Rate, Damage Cracking Strain - f(HA N2, Strain Rate), given DZ N2, Temperature, Damage Cracking Strain - f(HA N2, Damage), given DZ N2, Strain Rate, Temperature Cracking Strain - f(DZ N2, Temperature), given HA N2, Strain Rate, Damage Cracking Strain - f(DZ N2, Strain Rate), given HA N2, Temperature, Damage Cracking Strain - f(DZ N2, Damage), given HA N2, Strain Rate, Temperature

Cracking Strain - f(HA N2, DZ N2), given Strain Rate, Temperature, Damage

3.8 List of Hard Alpha Damage Contour Plots

All the hard alpha damage plots are included in APPENDIX 3: HARD ALPHA DAMAGE PLOTS.

List of plots:

Damage - f(Strain Rate, Temperature), given HA N2, DZ N2, Macro Strain Damage - f(Temperature, Macro Strain), given HA N2, DZ N2, Strain Rate D f(St i R t M St i ) i HA N2 DZ N2 T t

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Results are shown as contour plots of flow stress in temperature/strain rate. The strain and strain ratein these plots refer to macro values. The following conclusions were drawn:

With increasing macro strain, HA flow stress decreases due to increased damage and cracking.

Damage and cracking initiate at high strain rate and/or low temperature and spread to lowerstrain rates and higher temperatures with increasing macro strain.

The following plots are included in APPENDIX 4: Ti-64 AND HARD ALPHA FLOW STRESS

PLOTS.

HA vs Ti-64 Flow Stress at Macro Strain 0.05 HA vs Ti-64 Flow Stress at Macro Strain 0.25 HA vs Ti-64 Flow Stress at Macro Strain 0.50 HA vs Ti-64 Flow Stress at Macro Strain 1.00 HA vs Ti-64 Flow Stress at Macro Strain 1.50 HA vs Ti-64 Flow Stress at Macro Strain 2.00

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4.0 WORK ITEM 2: CRACKING STRAIN VS FORGING STRAIN

4.1 Objective

Evaluate the strain to hard alpha cracking relative to the strain produced during billet conversion

and during forging. Contours of strain during the forging of three generic non-proprietary shapeswill be obtained. Only one material (Ti-64) will be modeled. In general, each forging should be

modeled and the results evaluated on a case-by-case basis. The results obtained here will betypical of what to expect.

4.2 Accomplishments

A user subroutine was written to process the damage and strain to hard alpha cracking datain DEFORMTM. The subroutine creates contour plots of the hard alpha damage based on

the local forging temperature, strain and strain rate for given HA and DZ nitrogencontents. The damage values indicate the extent of cracking for the given HA and DZ

nitrogen contents. High damage values (approaching 1) indicate severe cracking whereaslow damage values (close to zero) indicate only the onset of cracking.

The model was validated using the data from the seeded dog-bone and back-flow forgingsfrom Phase I.

4.3 DEFORMTM

User Subroutine

The layout of the user subroutine is summarized below. A listing of the subroutine is provided in

APPENDIX 9: DEFORMTM SUBROUTINE.

1. Read damage rate and strain to cracking data on the first pass through this subroutine.

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3. The data read in step 1 is interpolated to the elemental strain, strain rate and temperature.

4. The interpolated damage is saved in four user defined variables at each element:

a) Damage at HA N2 = 4% and DZ N2 = 1%

b) Damage at HA N2 = 8% and DZ N2 = 1%c) Damage at HA N2 = 4% and DZ N2 = 3%

d) Damage at HA N2 = 8% and DZ N2 = 3%

5. Four contour plots of damage at the extremes of HA N2 and DZ N2 are obtained as

output.

6. These plots show the extent of cracking for anomalies with these nitrogen contents.

4.4 Model Validation

Macro forge models of the seeded mults SB1 - SB4 (dog-bone and reverse flow) werecompleted. These models were created in Phase I TRMD and were rerun using the strain to

cracking DEFORMTM user subroutine described above. The damage contours at the extremes ofHA N2 and DZ N2 are shown in Figure 8 and Figure 9.

A total of 44 seeds were fabricated, with/without diffusion zone, individual and clusters andforged in SB1 SB4 (Table 3). Twenty-eight (28) of the 44 seeds were cutup for detailedinvestigation of deformation and cracking.

SB1 (4 seeds cutup): seed numbers 1, 3, 4, 6. SB3 (12 seeds cutup): seed numbers 13-16, 17-20, 21-24. SB4 (12 seeds cutup): seed numbers 29-32, 33-36, 41-44.

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low (0.5), the correlation between damage and the extent of cracking isgood. At intermediate damage values (0.2 0.4), there is some scatter in the data.

Diffusion

Forging Seed # % N Zone Length, in Diameter, in

SB-1 1 1.5 Yes 0.200 0.2002 1.5 Yes 0.200 0.2003 12 Yes 0.200 0.200

4 12 Yes 0.200 0.200

5 12 No 0.200 0.1006 12 No 0.200 0.100

SB-2 7 1.5 Yes 0.200 0.200

8 1.5 Yes 0.200 0.2009 12 Yes 0.200 0.200

10 12 Yes 0.200 0.20011 12 No 0.200 0.100

12 12 No 0.200 0.100

SB-3 13-16 12 Yes 0.800 0.20017-20 12 Yes 0.800 0.200

21-24 12 Yes 0.800 0.20025-28 12 Yes 0.800 0.200

SB-4 29-32 12 Yes 0.800 0.200

33-36 12 Yes 0.800 0.20037-40 12 Yes 0.800 0.20041-44 12 Yes 0.800 0.200

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23

HAN2=4%; DZN2=1%

HAN2=4%; DZN2=3% HAN2=8%; DZN2=3%

HAN2=8%; DZN2=1%HAN2=4%; DZN2=1%HAN2=4%; DZN2=1%

HAN2=4%; DZN2=3%HAN2=4%; DZN2=3% HAN2=8%; DZN2=3%HAN2=8%; DZN2=3%

HAN2=8%; DZN2=1%HAN2=8%; DZN2=1%

Figure 8. Damage in SB1 SB3.

Damage increases with DZ N2% and with HA N2%.

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24

HAN2=4%; DZN2=3% HAN2=8%; DZN2=3%

HAN2=8%; DZN2=1%HAN2=4%; DZN2=1%

HAN2=4%; DZN2=3%HAN2=4%; DZN2=3% HAN2=8%; DZN2=3%HAN2=8%; DZN2=3%

HAN2=8%; DZN2=1%HAN2=8%; DZN2=1%HAN2=4%; DZN2=1%HAN2=4%; DZN2=1%

Figure 9. Damage in SB4.


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25

Radius (in) Radius (in)

He

ight(in)

Hei

ght(in)


He

ight(in)

Hei

ght(in)

Figure 10. Seed locations in forging SB1.

The figure on the left shows the initial seed locations, orientation and nitrogen content. Locations were measured by sonic inspection from the OD and are within

+0.125 in the scan direction. The figure on the right shows a comparison of the measured (indicated by an x and the letter m)and predicted seed locations (indicated by

the deformed rectangular shape and the lette r p). Locations were measured by sonic inspection from the top face and are within + 0.125 in the scan direction. The

measured and predicted locations agree well.

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26

HA 12% N2DZ 1.5% N2Axial

Damage 0.144

SB1, Seed 3

OD

ID

SB1, Seed 4

HA 12% N2DZ 1.5% N2Radial

Damage 0.405

OD

ID

SB1, Seed 6

HA 12% N2DZ 0% N2Circumferential

Damage 0.088

Seed mostly intact.Fractured across

diameter at fewlocations along length

OD

ID

HAN2=8%; DZN2=1%

HAN2=8%; DZN2=3%


Damage 0.144

SB1, Seed 3

OD

ID


Damage 0.144

SB1, Seed 3

OD

ID

OD

ID

SB1, Seed 4


Damage 0.405

OD

ID

SB1, Seed 4


Damage 0.405

OD

ID

OD

ID

SB1, Seed 6


Damage 0.088



OD

ID

SB1, Seed 6


Damage 0.088



OD

ID

OD

ID

HAN2=8%; DZN2=1%

HAN2=8%; DZN2=3%



Figure 11. SB1 Seeds: Comparison of predicted damage with extent of cracking.

Extent of cracking correlates approximately with hard alpha damage

Damage values at actual HA and DZ N2 contents.

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27


He

ight(in)

Height(in)


He

ight(in)

Height(in)




the deformed rectangular shape and the lette r p). Locations were measured by sonic inspection from the top face and are within + 0.125 in the scan direction. The


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28

HA 12 % N2DZ 1.5% N2Radial

ID

SB3-170.228

SB3-180.202

SB3-190.182

SB3-200.163

OD

SB3-210.122

HA 12 % N2DZ 1.5% N2Axial

SB3-230.125

SB3-220.123

SB3-240.126

ID Right sideOD Left side

SB3-14

HA 12 % N2DZ 1.5% N2CircumferentialDamage 0.205

OD

ID

circumference

SB3-13 SB3-15 SB3-16

HAN2=8%DZN2=1%

HAN2=8%DZN2=3%


ID

SB3-170.228

SB3-180.202

SB3-190.182

SB3-200.163

OD


ID

SB3-170.228

SB3-180.202

SB3-190.182

SB3-200.163

OD

SB3-210.122


SB3-230.125

SB3-220.123

SB3-240.126


SB3-210.122


SB3-230.125

SB3-220.123

SB3-240.126


SB3-14


OD

ID

circumference

SB3-13 SB3-15 SB3-16SB3-14


OD

ID

circumference

SB3-13 SB3-15 SB3-16

HAN2=8%DZN2=1%

HAN2=8%DZN2=3%


Extent of cracking correlates approximately with hard alpha damage .


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29


He

ight(in)

Height(in)


He

ight(in)

Height(in)




the deformed rectangular shape and the letter p). Locations were measured by sonic inspect ion from the top face and are within + 0.125 in the scan direction. The


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30


SB4-330.220

SB4-340.258

SB4-350.350

SB4-360.490ID OD

HA 12 % N2DZ 1.5% N2AxialDamage 0.852

SB4-41-44

Top Bottom

HA 12 % N2DZ 1.5% N2

CircumferentialDamage 0.818

SB4-32SB4-31SB4-30SB4-29

OD

ID

circumference

HAN2=8%DZN2=1%

HAN2=8%DZN2=3%


SB4-330.220

SB4-340.258

SB4-350.350

SB4-360.490ID OD


SB4-330.220

SB4-340.258

SB4-350.350

SB4-360.490ID OD


SB4-41-44

Top Bottom


SB4-41-44SB4-41-44

Top Bottom

HA 12 % N2DZ 1.5% N2


SB4-32SB4-31SB4-30SB4-29

OD

ID

circumference

HA 12 % N2DZ 1.5% N2


SB4-32SB4-31SB4-30SB4-29

OD

ID

circumference

HAN2=8%DZN2=1%

HAN2=8%DZN2=3%


Extent of cracking correlates approximately with hard alpha damage.


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31

Figure 16. Summary Predicted damage compared with photographs of extent of cracking for all seeds.

The seeds are arranged in order of increasing damage. The extent of cracking (as observed visually from the photographs) correlates approximately with hard alpha

damage. At low (0.5), the correlation between damage and the extent of cracking is good. At intermediate damage values (0.2 0.4), there is

some scatter in the data.

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5.0 WORK ITEM 3: CRACKING DURING BILLET CONVERSION AND

COMPONENT FORGING

5.1 Objective

Determine hard alpha nitrogen content which would not crack during billet and forgingconversions. A combination of the strain to cracking and the forging macro-strain data will be

used to determine the hard alpha nitrogen contents at which cracking occurs.

5.2 Accomplishments

Determined extent of hard alpha cracking during billet conversion and component forging.

Used three generic forging shapes as examples.

Modeled one material (Ti-64).

5.3 Ingot to Billet Conversion Damage

Damage was computed for the ingot to billet conversion process as described below:

Results based on 36 initial diameter.

For other diameters, these results apply for the same initial to final diameter ratio.

Based on uniform strain = ln(square of initial to final diameter ratio).

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5.4 Application of Damage and Cracking Strain to Forged Disks

Three generic forging shapes were used to illustrate the strain to cracking capability. In general,one should evaluate the results for any forging on a case-by-case basis. Strains during conversionof ingot to billet should be considered in addition to the component forging strains when

assessing the cracking of hard alpha anomaliess.

The first generic shape used was the seeded billet forgings SB1 SB4 from TRMD Phase I. Theother two shapes were Rolls-Royce forgings.

The two Rolls-Royce forgings which were modeled in Phase 1 (P/N 68696, AE 3007 fan disk

and P/N 68014, AE 2100/3007 Stage 14 compressor disk) were used as examples to illustrate theuse of the strain-to-cracking subroutines. The forgings are shown in Figure 17. In Phase I, areview of Rolls-Royce Allison fan rotor and compressor disk components resulted in theselection of these two components. The criteria for selecting the components were:

Must be in commercial service; Titanium alloy; Produced by press forging.

The fan disk is produced by Wyman-Gordon in Ti-64 alloy and the compressor disk is produced

by Sifco in Ti-6242 alloy. The fan disk is produced by press forging in a highly contoured closeddie. The compressor disk, being a relatively simple, flat shape, is press forged as a pancake inopen dies.

Roll-Royce worked with Wyman-Gordon and Sifco to establish DEFORMTM forging models for

each part. Both forgers use DEFORMTM in their forging die design operations and agreed to

share key word files with Rolls-Royce to run the models in-house. This was successfullyaccomplished and both models were run at Rolls-Royce. For the fan disk, Rolls-Royce used

proprietary Wyman-Gordon flow stress data for Ti-64 to run the macromodel. The data were

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Similar plots for the two Rolls-Royce forgings are shown in Figure 18 and Figure 19 and in

APPENDIX 6: DAMAGE, STRAIN, STRAIN RATE, AND TEMPERATURE CONTOURSPLOTS FOR RR P/N 68014, AE 2100/3007 STAGE 14 COMPRESSOR DISK and APPENDIX7: DAMAGE, STRAIN, STRAIN RATE, AND TEMPERATURE CONTOURS PLOTS FOR

RR P/N 68696, AE3007 FAN DISK.

Figure 17. (a) Fan Disk Forging. (b) Compressor Disk Forging.

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35

HAN2=4%; DZN2=3% HAN2=8%; DZN2=3%

HAN2=8%; DZN2=1%HAN2=4%; DZN2=1%

HAN2=4%; DZN2=3% HAN2=8%; DZN2=3%

HAN2=8%; DZN2=1%HAN2=4%; DZN2=1%

Figure 18. Damage - AE 2100/3007 Stage 14 compressor disk.


These plots show the damage only from the forging process.

Damage from the conversion process should be added to assess the extent of HA cracking.

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36

HAN2=4%; DZN2=3% HAN2=8%; DZN2=3%

HAN2=8%; DZN2=1%HAN2=4%; DZN2=1%

HAN2=4%; DZN2=3% HAN2=8%; DZN2=3%

HAN2=8%; DZN2=1%HAN2=4%; DZN2=1%

Figure 19. Damage - AE 3007 Fan disk.


These plots show the damage only from the forging process.

Damage from the conversion process should be added to assess the extent of HA cracking.

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5.5 Strain to Cracking Conclusions

The results of the present study show that ingot to billet conversion will, under commonly usedprocessing conditions, crack all hard alpha with nitrogen contents greater than 4%, which is the

lowest hard alpha nitrogen content evaluated here. The extent of cracking will be less if theconversion is carried out at high temperatures (~1750F) or low strain rates (~ 0.1/sec). Fornitrogen content less than 4%, the anomaly is treated as a diffusion zone. The diffusion zone

results from partially dissolved hard alpha cores during melting or conversion steps. If theanomaly is a diffusion zone only (without a hard alpha core), then the TRMD Phase I flow stresstests indicate that it has good ductility (Sections 3.3 and 3.4). The diffusion zone only anomaly is

unlikely to crack after billet conversion and forging; it would only deform along with the basematerial, but to a lesser extent depending on its nitrogen content. In reality there is no sharp

transition between a diffusion zone and a hard alpha at 4% nitrogen. The transition from ductileto brittle behavior occurs over a range of nitrogen contents depending on the deformationconditions (strain, strain rate, and temperature) and the beta to (beta + alpha) transition

temperature. More work is needed to accurately characterize the transition zone. Figure 20shows conceptually the dependence of cracking on nitrogen content in the diffusion zone and

hard alpha and the in-between transition zone.

Diffusion Zone Transition HACracked Diffusion Zone Transition HACracked

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6.0 WORK ITEM 4: ANOMALY ORIENTATION

6.1 Objective

Determine the orientations of melt-related anomalies in the conversion from ingot to billet and

also the conversion from billet to forging. The primary objective of this study would be todetermine if it would be likely that melt-related anomalies could end up oriented normal to

forging surfaces. Forging flow lines along which melt related anomalies tend to get oriented willbe predicted for the same three generic shapes defined in Work Item 3. Again, each forgingshould be modeled and the results evaluated on a case-by-case basis. The results obtained here

will be typical of what to expect.

6.2 Accomplishments

Predicted forging flow lines along which melt related anomalies tend orient.

Used same three generic forging shapes as in Work Item #3.

6.3 Results

Results for the seeded billet forgings SB1 SB4 are shown in Figure 21 and Figure 22.

Results for the two Rolls-Royce forgings are shown in Figure 23 thru Figure 26.

In some regions of these forgings, the flow lines are normal to forging surfaces. Melt-relatedanomalies which tend to orient along the flow lines might not be detectable if scanned from the

face to which the flow lines are normal. When flow lines are normal to a face, a scan fromh f h h ld b d

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39

Forging flow lines

normal to face Scan fromthis face

Forging flow lines


Forging flow lines


Forging flow lines


Figure 21. Flowlines in forgings SB1 SB4.

The sonic shape is shown by the inside solid lines.

The figure on the left show the initial parallel lines in the billet.

The figures on the right shows the deformed pattern in the forgings.

When flow lines are normal to a face, a scan from another face, or a shear scan should be used.

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40

Figure 22. Graphical display of overall deformation and orientation in forgings SB1 - SB4.

The figure on the left shows the initial circular pattern in the starting billet. The middle figure shows the deformed pattern in the dog-bone forgings SB1 SB3. The

figure on the right shows the deformed pattern in the backflow forging SB4. In all the three figures, the right half of forging shown and the symmetry centerline is on the

left edge. The three figures are to different scales.

These are the matrix material deformations and not the hard alpha deformations.

The deformed patterns correlate with grain deformation from macroslices.

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41

Forging flow linesnormal to faceForging flow linesnormal to faceForging flow linesnormal to faceForging flow linesnormal to face

Figure 23. Flowlines - AE 2100/3007 Stage 14 compressor disk.


The figure on the right shows the deformed pattern in the forging .


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42

Figure 24. Graphical display of overall deformation and orientation in AE 2100/3007 Stage 14 compressor disk.

The figure on the left shows the initial circular pattern in the starting billet. The figure on the right shows the deformed pattern in the forging. In both the three figures,

the right half of forging shown and the symmetry centerline is on the left edge.



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43

Forging flow lines

normal to face;Bore is probably

machined away

Forging flow lines

normal to face;Bore is probably

machined away

Figure 25. Flowlines - AE 3007 Fan disk.


The figure on the right shows the deformed pattern in the forging .


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44

Figure 26. Graphical display of overall deformation and orientation in AE 3007 Fan disk.

The figure on the left shows the initial circular pattern in the starting billet. The figure on the right shows the deformed pattern in the forging. In both the three figures,

the right half of forging shown and the symmetry centerline is on the left edge.



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7.0 SUMMARY AND CONCLUSIONS

In Phase I and earlier in Phase II of the TRMD program, a microcode was developed andvalidated to predict the size and orientation of hard alpha anomaliess. DOE (Design OfExperiments) based models were used to correlate anomaly deformation and forging macro

strain. This correlation predicts anomaly deformation quickly and accurately for both billetconversion and component forging and can be used to modify the anomaly distribution used in

lifing analyses.

As a follow-on, another activity was defined with the objective of determining the deformation

macro strain required to crack hard alpha anomalies in order to determine the likelihood of non-

cracked hard alpha under typical forming conditions. The results of this study are reported here.These results may direct the future development of NDE UT (Non-Destructive Evaluation Ultra-sonic) methods and/or changes to current inspection procedures to enhance anomalydetectability.

Hard alpha cracking strain and damage (extent of cracking) were determined as functions of

nitrogen content and deformation parameters. The model was validated with the limited seededbillet experimental data from TRMD Phase II. Extent of cracking correlates approximately with

hard alpha damage. Results are shown in a number of ways for ease of use and interpretation.

Strain to HA cracking increases and HA damage decreases with

decreasing HA N2 and decreasing DZ N2 content; increasing temperature; and decreasing strain rate.

For Ti-64, temperatures higher than 1700F and strain rates less than 0.5/second cause low

damage and cracking.

Damage and forging flow lines along which anomaliess tend to orient were computed for three

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The results of the present study show that ingot to billet conversion will, under commonly usedprocessing conditions, crack all hard alpha with nitrogen contents greater than 4%, which is the

lowest hard alpha nitrogen content evaluated here. The extent of cracking will be less if theconversion is carried out at high temperatures (~1750F) or low strain rates (~ 0.1/sec). Fornitrogen content less than 4%, the anomaly is treated as a diffusion zone. The diffusion zone

results from partially dissolved hard alpha cores during melting or conversion steps. If theanomaly is a diffusion zone only (without a hard alpha core), then the TRMD Phase I flow stress

tests indicate that it has good ductility (Sections 3.3 and 3.4). The diffusion zone only anomaly isunlikely to crack after billet conversion and forging; it would only deform along with the basematerial, but to a lesser extent depending on its nitrogen content. In reality there is no sharp

transition between a diffusion zone and a hard alpha at 4% nitrogen. The transition from ductile

to brittle behavior occurs over a range of nitrogen contents depending on the deformationconditions (strain, strain rate, and temperature) and the beta to (beta + alp ha) transitiontemperature. More work is needed to accurately characterize the transition zone.

The reasons for the discrepancies between the predictions and the measurements are:

Non-smooth hard alpha flow behavior with accumulated damage, especially at high N2content.

A wide range of the various independent variables fitted into a regression equation.

Inaccuracies in the constitutive property data obtained from a rather small number oftests.

Data smoothened and fitted into constitutive equation.

Cracking and voiding in hard alpha not captured.

Unknowns like pre-voiding, pre-cracking, fragmentation and reconstitution will influence

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8.0 ACKNOWLEDGEMENTS

The author would like to acknowledge technical discussions Jon Bartos (OSU/FAA) and JonTschopp (GEAE). Acknowledgements are also due to Joe Wilson and Tim Mouzakis at the FAAfor funding this effort and for technical discussions.

9.0 REFERENCES

1. Turbine Rotor Material Design, Final Report DOT/FAA/AR-00/64, December 2000.

2. S. Srivatsa, Turbine Rotor Material Design, Task 2, Effect Of Forging On DefectMorphology, Phase II Report, December 11, 2002.

3. K S Chan, L Perocchi, G R Leverant, Constitutive Properties of Hard-Alpha Titanium, MetTransactions A, Volume 31A, p3029, December 2000.

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10.0 APPENDIX 1: STATEMENT OF WORK DATED APRIL 9, 2003

The original statement of work dated April 9, 2003 is reproduced here. Some changes were madeto the approach (without changing the final deliverables) as the work progressed and these are

identified below.

10.1 Significance of this Task

The expected benefit of the strain-to-cracking studies is that the generic results will provideinsight into the likelihood of non-cracked HA under typical billet and forging conditions. Also,

expecting insight into the typical orientations of HA in forgings. The results of these studies maydirect the future development of NDE UT methods and/or changes to current inspection

procedures to enhance the detectability of HA in Titanium.

10.2 Work to be performed

1. Determine the relationship between hard alpha nitrogen content and strain to cracking using

TRMD data and the micro- and macro-codes. The strain to hard alpha cracking is a functionof the three variables: hard alpha nitrogen content, the deformation temperature and strain

rate. The results will be presented as contours of strain to hard alpha cracking as a function oftwo variables, with the third variable held constant. Examples are shown below:

Increasing strain

Strain

-Rate

Contours of Strain to Failureat a fixed N2 content

Increasing strain

Strain

-Rate

Contours of Strain to Failureat a fixed N2 content

Increasing strain

Strain

-Rate

Contours of Strain to Failure

at a fixed temperature

Increasing strain

Strain

-Rate

Contours of Strain to Failure

at a fixed temperature

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In general, each forging should be modeled and the results evaluated on a case-by-case basis.The results obtained here will be typical of what to expect.

3. Determine hard alpha nitrogen content which would not crack during billet and forging

conversions. A combination of the strain to hard alpha cracking and the forging macro-straindata will be used to determine the hard alpha nitrogen contents at which hard alpha crackingoccurs. This can be post-processed and be represented on the forging shape as a contour of

minimum hard alpha nitrogen content to hard alpha cracking.

Note: Initially the results were plotted as contours of hard alpha nitrogen content that would

not crack. However, it was found that the transition from cracking to no cracking occurs

over a narrow range of hard alpha nitrogen content resulting in very closely packed contours

in some regions of the forging. Therefore, this output was modified to produce contours of

damage which more quantitatively indicates the extent of cracking.

Contours of nitrogen content: hard alpha cracking will occur at a location for nitrogen contentsgreater than this

4. Determine the orientations of melt-related anomalies in the conversion from ingot to billet

and also the conversion from billet to forging. The primary objective of this study would beto determine if it would be likely that melt-related anomalies could end up oriented normal to

forging surfaces. Forging flow lines along which melt related anomalies tend to get orientedwill be predicted for the same three generic shapes defined in Item 2. Again, each forgingshould be modeled and the results evaluated on a case-by-case basis. The results obtained

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11.0 APPENDIX 2: STRAIN TO CRACKING PLOTS

In this appendix, all strain to cracking plots are included. The cracking strain is a function of the

five variables:

Hard alpha nitrogen content Diffusion zone nitrogen content Deformation temperature Deformation strain rate Critical damage defining extent of cracking

The cracking strain has been plotted as contours in two variables, holding the other three

variables at specified values.

The critical damage value in the plots indicates the extent of cracking achieved at the givencracking strain.

Damage = 0 (no cracking); and damage = 1 (fully cracked).

List of plots:

Cracking Strain - f(Strain Rate, Temperature), given HA N2, DZ N2, Damage Cracking Strain - f(Temperature, Damage), given HA N2, DZ N2, Strain Rate Cracking Strain - f(Strain Rate, Damage), given HA N2, DZ N2, Temperature Cracking Strain - f(HA N2, Temperature), given DZ N2, Strain Rate, Damage

Cracking Strain - f(HA N2, Strain Rate), given DZ N2, Temperature, Damage

Cracking Strain - f(HA N2, Damage), given DZ N2, Strain Rate, Temperature Cracking Strain - f(DZ N2, Temperature), given HA N2, Strain Rate, Damage C ki St i f(DZ N2 St i R t ) i HA N2 T t D

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Figure 33. Contours of strain to cracking as a function of strain rate and damage.

Strain to Cracking increases with increasing temperature (compare left/right figures).


Strain to Cracking decreases with increasing strain rate and with decreasing critical damage.

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Figure 34. Contours of strain to cracking as a function of strain rate and damage.



Strain to Cracking decreases with increasing strain rate and with decreasing critical damage.

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Figure 35. Contours of strain to cracking as a function of HA N2 and temperature.



Strain to Cracking decreases with increasing HA N2 % and with decreasing temperature.

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Figure 39. Contours of strain to cracking as a function of HA N2 and strain rate.



Strain to Cracking decreases with increasing HA N2 % and with increasing strain rate.

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Figure 43. Contours of strain to cracking as a function of HA N2 and damage.


Strain to Cracking decreases with increasing strain rate (compare top/bottom figures).

Strain to Cracking decreases with increasing HA N2 % and with decreasing critical damage.

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Figure 44. Contours of strain to cracking as a function of HA N2 and damage.



Strain to Cracking decreases with increasing HA N2 % and with decreasing critical damage.

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Figure 45. Contours of strain to cracking as a function of DZ N2 and temperature.



Strain to Cracking decreases with increasing DZ N2 % and with decreasing temperature.

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Figure 49. Contours of strain to cracking as a function of DZ N2 and strain rate.



Strain to Cracking decreases with increasing DZ N2 % and with increasing strain rate.

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Figure 53. Contours of strain to cracking as a function of DZ N2 and damage.



Strain to Cracking decreases with increasing DZ N2 % and with decreasing critical damage.

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Figure 54. Contours of strain to cracking as a function of DZ N2 and damage.



Strain to Cracking decreases with increasing DZ N2 % and with decreasing critical damage.

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Figure 55. Contours of strain to cracking as a function of HA N2 and DZ N2.



Strain to Cracking decreases with increasing HA N2 % and with increasing DZ N2 %.

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12.0 APPENDIX 3: HARD ALPHA DAMAGE PLOTS

In this appendix, all hard alpha damage plots are included. The HA damage is a function of the

five variables:

Hard alpha nitrogen content Diffusion zone nitrogen content Deformation temperature Deformation strain rate Macro strain

The HA damage has been plotted as contours in two variables, holding the other three variables

at specified values.

The HA damage value in the plots indicates the extent of cracking achieved at the given macrostrain.

Damage = 0 (no cracking); and damage = 1 (fully cracked).

List of plots:

Damage - f(Strain Rate, Temperature), given HA N2, DZ N2, Macro Strain Damage - f(Temperature, Macro Strain), given HA N2, DZ N2, Strain Rate Damage - f(Strain Rate, Macro Strain), given HA N2, DZ N2, Temperature Damage - f(HA N2, Temperature), given DZ N2, Strain Rate, Macro Strain Damage - f(HA N2, Strain Rate), given DZ N2, Temperature, Macro Strain

Damage - f(HA N2, Macro Strain), given DZ N2, Strain Rate, Temperature Damage - f(DZ N2, Temperature), given HA N2, Strain Rate, Macro Strain D f(DZ N2 St i R t ) i HA N2 T t M St i

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Damage increases with increasing HA N2 % (compare

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