Principles of Engineering P3 - - TU · PDF filePrinciples of Engineering P3 Prof. Dr.-Ing....

Principles of Engineering P3

Prof. Dr.-Ing. habil. Dietmar Eifler

Dr.-Ing. Frank Balle, Dipl.-Ing. Sebastian Schuff

Characterization of local mechanical properties of

multiphase metallic materials related to RTG 1932

Topics

Multiphase metallic materials

Metal matrix composites

Microscopic characterization of heterogeneous materials

Stress-strain behavior of multiphase materials

Micro-deformation in multiphase materials

Micro-deformation mapping and up-scaling on macro as well as component level

3

Topics







4

Educational objectives of materials science and engineering

5

Education in

Manufacturing

Structure / microstructure

Properties

Applications

development of chemical and physical basics of materials science

Application of knowledge to solve technical challenges related to materials science and engineering

Requirements for engineering materials

Engineering components and products must

resist monotonic and cyclic stresses,

combined with specific environmental

conditions like:

temperature, humidity etc.

withstand loading conditions in terms of

abrasion, erosion and corrosion

be processible and machinable

be re-usable (recyclable)

6

Design Manufacture

Material

Component

Examples for the use of highly stressed materials

7

Steam turbine Modern high speed train

Test stand for brakes Commerical aircrafts

Density in kg/m3

You

ng‘s

mod

ulus

in

GP

a

Overview of present material groups

8[CES EduPack]

Classifications for metallic materials

Density Light alloys < 5 g/cm³ (e.g.: Mg 1.7, Al 2.7, Ti 4.5)

Heavy metals > 5 g/cm³ (e.g.: Fe 7.8, Cu 8.9, Ta 16.6, Os 22.5)

Alloy system

Ferrous alloys (e.g.: carbon steels, low- and high-alloy steels)

Nonferrous alloys (e.g.: AA1050, Ti6Al4V)

Number of phases

Single-phase (homogeneous) materials (e.g.: pure aluminum, CuZn20)

Multi-phase (heterogeneous) materials (e.g.: AMC 217xe)

Manufacturing

Metal forming wrought alloy (e.g.: AA2124)

Sintering sintering alloy (e.g.: WC)

Casting casting alloy (e.g.: AlSi12)

9

Binary phase diagram

Elements A and B

Completely soluble in liquid condition

In solid condition limited soluble in each other (eutectic reaction)

10

CB in weight-%

Binary phase diagram:Aluminum - Copper

11

[CES Edu Pack]

Lattice structure, crystal system

12

a0

b0 = a0

c0 = a0

Face-centered cubic lattice (fcc)e.g. aluminum

Notation of lattice planes

°

{111}

{101}

{001}

x

y

z

Defects in crystalline materials

Point defects (1D)

Linear defects (2D)

13

Vacancy Interstitial atom

Substitutionalatom

Interstitialatom

Twin boundary

Zone

Small angle boundary Large angle boundary

Spatial defects (3D)

Micro crack

Precipitationordispersion

Dislocations –one-dimensional imperfections

14

Linear lattice defects are necessary for mechanical deformation

Edge dislocation: dislocation line perdendicular to Burgers vector

Screw dislocation: dislocation line parallel to Burgers vector

Hardening mechanisms #1

Solid solution hardening

Dislocations have to pass obstacles (e.g. foreign atoms) in their slip plane

Material resistance can be calculated as

′with: parameter depending on size effect δ and modulus effect η

shear modulus′ concentration of foreign atoms

constant ( ⁄ 1)

15

Hardening mechanisms #2

Precipitation hardening

Precipitations reduce the mobility of dislocations

The aim is a high volume-% of small precipitations to increase the material resistance

16

- partially coherentprecipitations(particles)

- coherentprecipitations(particles)

- noncoherentprecipitations(particles)

Schematic microstructure of polycrystalline metals

17

Substitutionalatom

Vacancy

Unit cell

Interstitial atom

Edge dislocation

Noncoherentprecipitations

Screw dislocation Grain boundaryprecipitation

Slip lines

High-meltingsecond phase

Coherent precipitations, orientated by the lattice,

Topics







18

Overview of multi-phase composite materials

19Density in kg/m3

You

ng‘s

mod

ulus

in

GP

a

Polymers

MetalsPolymer Matrix

Composites

Metal Matrix Composites

[CES EduPack]

Motivation for the use of metal matrix composites

201000 10000

10

100

1000UHM (f)

HM (f)

Carbon fibers

UHS (f)

HS (f)Nicalon (f)Boron

B (f)B (w)

Silicon carbide Al₂O₃ (w)

SiC (w)SiC (p)

Diamond (p)

Alumina

Silicon nitride

Al₂O₃ (f)Al₂O₃ (p)

TiC (p) ZrC (p)

WC (ρ=15.6)

Tungsten (ρ=19.3)

Tantalum(ρ=16.8)

Steels

ZrO₂ (p)

Titaniumalloys

Asbestos (f)Si (f)

SiliconM

SE

A

CGlass fibers

SilicaAluminum

alloys

Magnesium alloys

Cellulose (f)

29

49

Kevlar (f)

UDPE (f) (ρ=0.97)

Density in kg/m3

You

ng‘s

mod

ulus

in G

Pa

SiC (f)

[CES EduPack]

Engineering applications for composite materials

21

[Airbus Group]

[Sauber Formel 1][CeramTec]

Motivation for metal matrix composites

22

1 1

2

Layer Composite Fiber Composite Particle Composite

Microstructure

Characteristics Reinforcement layer as coating or alternating

Thin (dis-)continuous fibers (few µm)

Fine particles,stochastically distributed

Example Sandwich structures Al-oxide fibers Carbide particles in Al-matrix

Types of reinforcement for composites

23

Aluminum wrought alloy AA2124

24

Material properties

Main alloy component copper (series 2xxx)

Density 2.78 g/cm³

Young‘s modulus 73.1 GPa

UTS 483 MPa

Hardness 146 HV

Melting point ≈ 600 °C

Chemical composition

Wt.-% Al Cu Mg Mn Fe Si Cr Zn

AA2124 basis 4.24 1.34 0.76 0.17 0.09 0.06 0.04

[CES EduPack]

Silicon carbide particles

25

Material properties

Most important nonoxide ceramic

Molecular formula SiC

Density ≈ 3.21 g/cm³

Young‘s modulus ≈ 400 GPa

Hardness ≈ 2600 HV

Melting point decompositionover 2700 °C

Manufacturing

Acheson-method

Quartz sand and petrol coke

Chipped wood to generate pores for degassing

Temperatures from 2000°C to 2400°C by carbo-thermal reduction

3 → 2

10 µm

[CES EduPack]

[M. Wolf, WKK]

Manufacturing of Al-Matrix-Composites

Benefits

Increase of Young‘s modulus

Increase of ultimate tensile strength

Increase of erosion resistance

26

Metal powder(aluminum)

Carbide Particles

(SiC)

High energymixing

Solid statecompression

Billet

Extrusion

Matrix: Aluminum Alloy 2124 T6

[AMC Composites, UK]

Al-Matrix-Composites in P3

27

17

0.73.5 0.3

Vo

lum

e fr

acti

on

SiC

in %

Particle size SiC in µm

AMC 217xeAMC xfine217

AMC xxfine217

5 µm

AMC 217xe: cross section AMC xfine217: cross section

5 µm

SiC particlesAluminum

matrix alloy

Material properties of Al-Matrix Composites used in P3

28

Unit AMC 217xe AMC 217xfine

Density g/cm³ 2.82 2.80

Young‘smodulus

GPa 104 102

Poisson ratio 0.32 0.34

Yield strength MPa 399 465

UTS MPa 589 644

Hardness HV 30 174 186

[S. Schuff, M. Wolf, WKK]

Topics







29

Different microscopic resolution limits

30

[nach Guy, A.: Metallkunde für Ingenieure]

macroscopic light-microscopic electron-microscopic atomic

Different microscopic resolution limits:Examples

31

Broken gear box shaft Microstructure of Al alloy AA5454

50 µm

Macroscopic Light microscope

Scanning electronmicroscope (SEM):Human hair

Cutting

Cooling liquid to avoid changes in microstructure and to flush out abrasion

Mounting

Easy handling of specimen

Hot mounting: Pressure and temperature to melt granulate resin

Cold mounting: Combination of resin and hardener

Metallographic preparation

32

[Struers]

Metallographic preparation

33

Grinding

Abrasive particles are used in successively finer steps

Polishing

To remove marks from grinding and obtain a highly reflective surface for microscopy

10 mm 10 mm

Metallographic orientations ofextruded AMC

Longitudinal-section: plane x-z Cross-section: plane y-z

34

z

y

x

5 µm5 µm

Topics







35

Tensile test

One of the most important destructive tests

Standardized in DIN EN 10 002, part 1

Material behavior in uniaxial direction under monotonic load

Determination of material characteristics, which are an important basis for dimensioning of engineering components

Quantities to be measured: - Force- Elongation

36

Linear elastic properties

Horizontal cut

Cut face = A0

Cutting force (F A0): F = F

Cutting force (F A0): F|| = 0

Normal stress:

No shear stress, because F|| = 0.

37

FA0

F

F

F

Global mechanical properties of heterogeneous engineering materials

Definition of mechanical properties

Engineering stress

Engineering strain

Yield strength

Young‘s modulus

Ultimate tensile strength

38

UTS

yspecimen failure

∆

∆

Why do we need fatigue tests?

39

Fatigue cracks nearby doors andwindows of the first passengerjetliner Comet

Aloha-Airlines-Flight 243 of a Boeing 737-200on April 28th 1988 from Hilo to Honolulu After climbing a part of the fuselage area

In the front part of the aircraft broke out

Dynamic crack

Constant amplitude test

maximum stress

minimum stress

stress amplitude

2mean stress

2stress ratio

period of oscillation

1 2

frequency

40

S-N diagram

Aim:

41

Determination of the fatigue strength RD of a material

Sufficient number of specimens under identical loading conditions

Constant stress amplitude a with the same mean stress m

Tests untill specimen failure (NB) or to an ultimate number of cycles (NG)

Approach:

S-N diagram: Type I

Ferritic-pearlitic steels

Tempered steels

Many Cu-alloys

fatigue strength

42

S-N diagram: Type II

fcc-metals (Al, Cu)

Austenitic steels

/ fatigue strength

43

Topics







44

Comparison of macroscopic and microscopic view

45

10 µm

1 mm

10 mm

Propagation of fatigue cracks

State I

Along slip planes

Small crack length

State II

Normal to loading direction

46

State I

State I

State II

[C.-P. Fritzen, University of Siegen]

Crack growth from initiation to failure

47

Cra

ck le

ngth

a

Number of cycles N

FailureLong crack propagation

Micro crack propagation

Crack initiation

State II[U. Krupp, Hochschule Osnabrück]

Micro cracks

Local material discontinuity with finite length

Endless sharp crack tip

Crack surface spacing 0

48

2b x

zy

n

xy

2a

2b

y

x

Crack surfacespacing 0

Crack tip with curvature radius 0 (with from ellipse equation)

→ ∙

Stress intensity

49

At positions y = 0 and x = ±a stress peaks occur because of the notch effect

12

12

1 2

By transformation of equation (1) via multiplication with :

12

12

12

12

Stress intensity ⁄

Describes stress field around the crack tip

(1)

Crack propagation diagram

50

[S. Suresh]

region A region B

region C

da/

dN

in m

m/c

ycle

log ∆K

K0

l

m

KC

⁄

∆

Upscaling from micro tensilespecimen to component level

5120 mm 50 mm

[Materion]

Topics







53

Specimen preparation out of extruded AMC

54

z

y

x

Topview on a micro tensile specimen

Plane: x-y

55

y

z x

FX (>0)FX (>0)

FX (>0)

1 mm

FX (>0)

Micro tensilespecimen

Mechanical loading system

Mechanical loading system forinsitu experiments

56

50 mm

[M. Schrader, WKK]

Micro tensile test on AMC 225xe

[M. Schrader, WKK]

F0 = 0 N

10 µm

Fmax = 4050 N

10 µm

57

4000

4000

Fo

rce

in N

Elongation in µm

100 200 300

3000

2000

1000

0

Fmax

F0

Movement u1 in x-direction

58

[J. H. Fitschen, P3]

Strain

59

[J. H. Fitschen, P3]

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