www.sciencemag.org/content/355/6329/1055/suppl/DC1

Supplementary Materials for

Bone-like crack resistance in hierarchical metastable nanolaminate steels

Motomichi Koyama,* Zhao Zhang, Meimei Wang,* Dirk Ponge, Dierk Raabe, Kaneaki Tsuzaki, Hiroshi Noguchi, Cemal Cem Tasan*

*Corresponding author. Email: koyama@mech.kyushu-u.ac.jp (M.K.); wang@mit.edu (M.W.);

tasan@mit.edu (C.C.T.)

Published 10 March 2017, Science 355, 1055 (2017) DOI: 10.1126/science.aal2766

This PDF file includes:

Materials and Methods Supplementary Text Figs. S1 to S8 Tables S1 and S2 References

2

Materials and Methods

Materials

The ferrite-martensite Fe–0.9C–1.7Mn–0.24Si (wt.%) dual phase (DP) steel (Fig. 1C)

was produced by intercritical annealing at 1023 K and follow-up quenching to room

temperature. The ferrite-cementite Fe–0.9C–0.9Mn–0.4Si (wt.%) pearlitic steel (Fig. 1D)

was heat treated at 1200 °C for 30 min, followed by 650 °C for 3 min, and quenched in

water. The pearlite block size and lamellar spacing were approximately 75 μm and 0.15

μm, respectively. The metastable multiphase martensite-austenite TRIP steel (Fig. 1E) had

a chemical composition of Fe-9Mn-3Ni-1.4Al-0.01C (wt. %). The steel was cast and hot

rolled at 1373 K. Afterwards, it was homogenized at 1373 K for 1 hour and subsequently

water-quenched. The as-quenched steel plate was cold rolled by 70% thickness reduction.

Partial reversion of cold-rolled αʹ-martensite to austenite was carried out at 873 K for 1 h

(37: M.-M. Wang, C.C. Tasan, D. Ponge, D. Raabe, Spectral TRIP enables 1.1 GPa

martensite. Acta Materialia 111, 262-272 (2016).). The new metastable multiphase

nanolaminate steel (Fig. 1F) introduced in this study has a Fe-9Mn-3Ni-1.4Al-0.01C

(wt.%) composition. The steel was cast and hot rolled at 1373 K. Afterwards, it was

homogenized at 1373 K for 1 hour and subsequently water-quenched. The as-quenched

microstructure was fully lath martensitic. For obtaining reversed austenite with different

volume fractions, the as-quenched martensite bulk specimens were annealed at 873 K for

1 and for 8 hours, respectively (17, 18). This treatment produced a martensitic matrix with

austenite islands at various martensitic boundaries. The latter can be classified into two

groups based on their size: those that range between 0.1 - 0.3 μm2 and the others that are

between 0.3 - 4.0 μm2. As reference material in Fig. 2 we use a DP steel with coarse and

equiaxed grain shape. Specific martensite or ferrite morphologies such as laminated α/α’

that can deflect the fatigue crack path provide similar fatigue crack resistance to pearlitic

steels. Other mechanical tests of the metastable multiphase nanolaminate steels reveal

improvements in fracture toughness as well as in tensile elongation (18).

Methods

Fatigue properties were evaluated by rotary bending fatigue testing at 50 Hz at room

temperature (≈ 298 K). The stress ratio, R, was −1, and a sinusoidal waveform was

employed. The stress ratio is defined as the minimum stress divided by the maximum

stress. To reduce the effect of temperature increase during testing, the specimens were

cooled by an electric fan. The fatigue cracks were observed by optical microscopy using

the replica technique (38: S. Hamada et al., Strain mapping with high spatial resolution

across a wide observation range by digital image correlation on plastic replicas. Materials

Characterization 98, 140-146 (2014).). Prior to testing, the specimens were mechanically

polished with emery papers and colloidal silica. The polished specimens were chemically

etched with 3% nital to reveal the microstructures. In terms of instrumentation, we used an

Ono-type rotary bending fatigue test machine (specimens were clamped on both sides.)

(39: M. Ohnami, Fracture and society, IOS Press, 180 (1992).). The specimen geometry is

given in Fig. S1. After fatigue testing, sample surface was prepared following standard

metallography procedures. Samples were prepared by grinding, polishing in diamond

suspension and final polishing in colloidal silica suspension. The last step ensures obtaining

a deformation-free surface.

In addition, to clarify the high importance of the nanolaminate microstructure

3

morphology for the improved properties, we carried out corresponding fatigue tests also

for the same material, yet, with non-laminated metastable multiphase microstructure

presented in Fig. 1E. Since the design of the non-laminated metastable multiphase

microstructure requires cold rolling, the resulting specimen geometry is always a plate.

Therefore, the fatigue test plate specimen was fixed on the round bar jig as shown in Fig.

S3, and fatigue tests were performed on an Ono-type rotating bending fatigue testing

machine at room temperature with a stress ratio of −1 and a frequency of 30 Hz. Results of

this additional experiments are presented in Fig. S4. All of the results presented in Fig. S4

were obtained from the same plate specimen geometry and testing method.

Microstructures were characterized by scanning electron microscopy based EBSD at

15 kV at a beam step size of 80 nm and ECCI at 20 kV. Samples for the SEM analyses

were prepared by grinding, polishing in diamond suspension and final polishing in colloidal

silica suspension.

Supplementary Text

Fatigue crack closure

In this study, we observed crack termination associated with roughness of the crack

surface and metastability of austenite. The termination mechanisms of fatigue cracks

observed here have been understood as crack closure effects, which is different from the

crack arrest mechanisms observed in fracture toughness testing. Since fatigue cracks are

re-sharpened by compression, fatigue crack growth cannot be terminated by crack blunting

which typically reduces stress concentration at a crack tip. Instead, cyclic loading produces

compressive residual stresses on a crack surface, suppressing plastic deformation at a crack

tip during crack opening. This mechanism is typically referred to as plasticity-induced

crack closure. Volume expansion by αʹ-martensitic transformation enhances this crack

closure effect, a mechanism which is then referred to as transformation-induced crack

closure (25, 28, 29). Crack surface roughness also contributes to the enhancement of the

crack closure properties through strengthening effects contributed by compressive residual

stresses and friction stresses acting on the crack surface (24, 27). Specifically, fatigue

cracks are terminated when the following conditions are satisfied.

1) Dislocation emission at a fatigue crack tip does not occur. 2) Brittle cracking does not occur Even when a fatigue crack is not terminated, the fatigue crack growth is decelerated by

the crack closure effects, improving fatigue life.

Difference between rotary bending fatigue and pull-push fatigue tests

There is a difference between the rotary bending fatigue test and the pull-push fatigue

test due to the presence of stress gradients (40: D.C.R. Waryoba, J.S. Mshana, Effect of

size and stress gradient on fatigue behavior. International Journal of Pressure and Piping

60, 177-182 (1994).). Yet, this effect does not change the order and trend of fatigue life

and fatigue limit values obtained on specimens without notch in the comparison shown in

Fig. 2. Stress gradients lead to slightly higher fatigue strength values in rotary bending

fatigue tests (Fig. S5). Here, we consider effects of stress gradients on fatigue limit and

fatigue life separately. The fatigue limits presented in this study are determined by fatigue

crack initiation and non-propagation limits. The length of a non-propagating crack that

4

must be considered for fatigue limit is less than 140 μm as demonstrated in Fig. 3d.

Assuming a half-penny shaped crack, the depth of the small crack is 70 μm when counted

from the specimen surface. This means that a reduction in stress pertaining to the stress

gradient is negligibly small in the current case, which does not affect the small crack

behavior. Also for fatigue life, the major portion of the life span is composed of (a) the

fatigue crack initiation life span and (b) the small fatigue crack propagation life span. In

fact, 80% of the total fatigue life value is dominated by fatigue crack growth until 1 mm as

shown in Fig. S6. More specifically, for the case of fatigue life, the depth of the crack is

around 500 μm, which is still a small effect on stress reduction. The reminder of the 20%

of the fatigue life span may be influenced by the effect of stress gradients, which means

that the fatigue life span presented in this study may be overrated slightly. However, all the

other reference data used in this study were taken by the same experimental method and

on specimens with similar geometry. Therefore, the difference between rotary bending

fatigue testing and push-pull testing similarly affects respective experimental results of the

resent alloys and reference materials.

Comparison of the current findings with the properties of other conventional structural

materials

The data sets shown in Fig. S7 provide a wider comparison range in fatigue properties

of our new hierarchical nanolaminate steel with other structural materials including type

304 austenitic steel and Ti-based alloys. Even compared to the austenitic steels and Ti-

based alloys, the fatigue life values of the present metastable multiphase nanolaminate

steels are concluded to be superior particularly at high stress amplitudes.

Crack surface roughness and its effect on crack motion

Fig. S8 shows a SEM image showing a sub-crack with a distinct roughness in the

metastable multiphase nanolaminate steel. As indicated by the yellow arrows, some parts

of the crack surfaces contact each other, while other portions do not. The mismatch between

the crack surfaces during crack opening and closing processes prevents fatigue crack

growth, a mechanism which has been referred to as roughness-induced crack closure (25).

5

Fig. S1

A schematic sketch of the specimen geometry used for the rotary bending fatigue tests.

6

Fig. S2

Replica images showing fatigue crack initiation at a non-metallic inclusion of the presented

steel aged for 1 h tested at 500 MPa. (A) Before and (B) after testing until 2×105 cycles.

7

(A)

(B)

Fig. S3

(A) A schematic sketch of the plate specimen geometry used for the fatigue tests (unit:

mm). A jig shown in (B) was used to test samples taken from the plate specimens by

rotating bending fatigue testing. The plate specimen was fastened on the jig by screws.

8

Fig. S4

Stress amplitude vs. number of cycles to failure diagram of the presented steel in a

microstructural state once with and once without a nanolaminate microstructure.

9

Fig. S5

Comparison between fatigue strength values measured by rotary bending fatigue testing

and by pull-push fatigue testing (41: T. Araki, NRIM Fatigue Data Sheet No. 2, (National

Research Institute for Metals, 1978). 42: T. Araki, NRIM Fatigue Data Sheet No. 3,

(National Research Institute for Metals, 1978). 43: T. Araki, NRIM Fatigue Data Sheet No.

4, (National Research Institute for Metals, 1978). 44: S. Nishijima, Fundamental fatigue

properties of JIS steels for machine structural use, NRIM fatigue data sheet technical

document No. 5, (National Research Institute for Metals, 1981).). The chemical

compositions of these steels are listed in Table S1.

10

Fig. S6

Fatigue crack length plotted against number of cycles at 760 MPa observed in the new

metastable nanolaminate steel aged for 1 h.

11

Fig. S7

Comparisons of fatigue life values determined for various materials including type 304

austenitic steel (45: N. Hattori, S. Nishida, A. Takahashi, Effect of structure stability on

fatigue properties of austenite stainless steels. Transaction of the Japan Society of

Mechanical Engineering Series A 65, 340-344 (1999).) and Ti-based alloys (46: L.

Wagner, Mechanical surface treatments on titanium, aluminum and magnesium alloys.

Materials Science and Engineering A 263, 210-216 (1999)). Some of data obtained for the

12

Ti-based alloys and for the type 304 steel were tested with the same method as the samples

of the new metastable multiphase nanolaminate steels in our laboratory. The chemical

compositions of the steels tested in our laboratory are listed in Table 2.

13

Fig. S8

SEM image showing roughness and associated crack surface contact of the presented steel

aged for 1 h tested at 800 MPa. The yellow arrows specifically indicate parts of the crack

surface contacting each other. The specimen surface was mechanically polished up to depth

of 48 μm and subsequently etched by 3% nital after the fatigue test. This crack is one of

the sub-cracks that exist after the failure.

14

Table S1.

Chemical compositions (wt. %) of the steels used for Fig. S5 (41: T. Araki, NRIM Fatigue

Data Sheet No. 2, (National Research Institute for Metals, 1978). 42: T. Araki, NRIM

Fatigue Data Sheet No. 3, (National Research Institute for Metals, 1978). 43: T. Araki,

NRIM Fatigue Data Sheet No. 4, (National Research Institute for Metals, 1978). 44: S.

Nishijima, Fundamental fatigue properties of JIS steels for machine structural use, NRIM

fatigue data sheet technical document No. 5, (National Research Institute for Metals,

1981).). The steels marked by yellow and gray were used for determining fatigue strength

data at 105 and 2×107 cycles, respectively. -: Not examined

C Si Mn P S Ni Cr Mo Cu

S35C

A 0.35 0.21 0.77 0.021 0.022 0.01 0.01 - 0.02

B 0.35 0.30 0.74 0.017 0.024 0.01 0.10 - 0.01

C 0.34 0.26 0.74 0.012 0.015 0.01 0.02 - 0.01

D 0.36 0.26 0.70 0.009 0.023 0.08 0.12 - 0.09

S45C

A 0.45 0.25 0.79 0.018 0.016 0.02 0.13 - 0.02

B 0.45 0.26 0.76 0.027 0.019 0.01 0.11 - 0.02

C 0.45 0.24 0.71 0.010 0.009 0.12 0.06 - 0.13

D 0.44 0.24 0.82 0.021 0.021 0.03 0.02 - 0.03

S55C

A 0.55 0.23 0.76 0.018 0.012 0.01 0.09 - 0.01

B 0.54 0.26 0.76 0.022 0.021 0.02 0.12 - 0.01

C 0.52 0.29 0.83 0.016 0.025 0.04 0.04 - 0.02

D 0.56 0.26 0.67 0.019 0.026 0.04 0.13 - 0.11

S35C Max 0.38 0.30 0.82 0.031 0.030 0.08 0.12 - 0.11

Min 0.32 0.21 0.63 0.007 0.013 Ni + Cr = 0.02～0.20 - 0.01

S45C Max 0.49 0.26 0.83 0.027 0.025 0.13 0.13 - 0.15

Min 0.42 0.22 0.70 0.010 0.009 Ni + Cr = 0.03～0.18 - 0.01

S55C Max 0.57 0.30 0.83 0.024 0.026 0.06 0.13 - 0.22

Min 0.52 0.20 0.67 0.009 0.012 Ni + Cr = 0.02～0.17 - 0.01

SMn438 Max 0.46 0.27 1.59 0.017 0.019 0.06 0.22 - 0.08

Min 0.38 0.21 1.34 0.011 0.007 0.02 0.03 - 0.02

SMn443 Max 0.46 0.34 1.60 0.027 0.022 0.10 0.27 - 0.10

Min 0.40 0.21 1.36 0.008 0.007 0.02 0.04 - 0.01

SCr440 Max 0.43 0.32 0.81 0.022 0.014 0.07 1.12 - 0.13

Min 0.39 0.22 0.71 0.010 0.004 0.02 0.94 - 0.01

SCM435 Max 0.38 0.35 0.82 0.026 0.022 0.12 1.09 0.19 0.19

Min 0.33 0.23 0.69 0.012 0.007 0.01 0.97 0.15 0.01

SCM440 Max 0.44 0.29 0.87 0.024 0.028 0.24 1.10 0.22 0.15

Min 0.37 0.22 0.69 0.010 0.004 0.02 0.94 0.15 0.02

SNC631 Max 0.35 0.30 0.65 0.019 0.016 2.78 0.89 - 0.10

Min 0.28 0.22 0.49 0.008 0.004 2.63 0.71 - 0.05

SNCM439 Max 0.43 0.33 0.79 0.022 0.021 1.92 0.96 0.24 0.12

Min 0.37 0.19 0.68 0.010 0.004 1.62 0.68 0.16 0.03

SNCM447 Max 0.49 0.29 0.79 0.014 0.016 1.80 0.79 0.20 0.11

Min 0.44 0.16 0.69 0.009 0.009 1.65 0.71 0.16 0.05

SUS403 Max 0.15 0.50 0.83 0.029 0.023 0.31 12.70 0.15 -

15

Min 0.09 0.21 0.32 0.016 0.002 0.08 11.65 0.02 -

16

Table S2.

Chemical compositions of the reference materials for Fig. S7. -: Not examined.

Fe C Mn P S Ni Cr Ti Al N O V

Type 304

austenitic

steel

Bal. 0.046 0.84 0.02 0.005 8.7 18.42 0.002 0.001 0.044 - -

Ti-based

alloy 0.225 - - - - - - Bal. 6.29 - 0.155 4.35

References and Notes

1. Y. D. Wang, H. Tian, A. D. Stoica, X.-L. Wang, P. K. Liaw, J. W. Richardson, The development of grain-orientation-dependent residual stresses in a cyclically deformed alloy. Nat. Mater. 2, 101–106 (2003). doi:10.1038/nmat812 Medline

2. D. S. Kemsley, Interior deformation markings in copper fatigue specimens. Nature 178, 653–654 (1956). doi:10.1038/178653a0

3. H. Mughrabi, Cyclic slip irreversibility and fatigue life: A microstructure-based analysis. Acta Mater. 61, 1197–1203 (2013). doi:10.1016/j.actamat.2012.10.029

4. S. Timoshenko, History of Strength of Materials: With a Brief Account of the History of Theory of Elasticity and Theory of Structures (Courier Corporation, 1953).

5. C. M. Sonsino, Course of SN-curves especially in the high-cycle fatigue regime with regard to component design and safety. Int. J. Fatigue 29, 2246–2258 (2007). doi:10.1016/j.ijfatigue.2006.11.015

6. K. S. R. Chandran, Duality of fatigue failures of materials caused by Poisson defect statistics of competing failure modes. Nat. Mater. 4, 303–308 (2005). doi:10.1038/nmat1351 Medline

7. A. Pineau, D. L. McDowell, E. P. Busso, S. D. Antolovich, Failure of metals II: Fatigue. Acta Mater. 107, 484–507 (2016). doi:10.1016/j.actamat.2015.05.050

8. H. Peterlik, P. Roschger, K. Klaushofer, P. Fratzl, From brittle to ductile fracture of bone. Nat. Mater. 5, 52–55 (2006). doi:10.1038/nmat1545 Medline

9. R. K. Nalla, J. H. Kinney, R. O. Ritchie, Mechanistic fracture criteria for the failure of human cortical bone. Nat. Mater. 2, 164–168 (2003). doi:10.1038/nmat832 Medline

10. P. Fratzl, R. Weinkamer, Nature’s hierarchical materials. Prog. Mater. Sci. 52, 1263–1334 (2007). doi:10.1016/j.pmatsci.2007.06.001

11. R. O. Ritchie, The conflicts between strength and toughness. Nat. Mater. 10, 817–822 (2011).

12. L. L. Li, P. Zhang, Z. J. Zhang, Z. F. Zhang, Intrinsically higher fatigue cracking resistance of the penetrable and movable incoherent twin boundary. Sci. Rep. 4, 3744 (2014). Medline

13. Z. Ma, J. Liu, G. Wang, H. Wang, Y. Wei, H. Gao, Strength gradient enhances fatigue resistance of steels. Sci. Rep. 6, 22156 (2016). doi:10.1038/srep22156 Medline

14. Y. Kimura, T. Inoue, F. Yin, K. Tsuzaki, Inverse temperature dependence of toughness in an ultrafine grain-structure steel. Science 320, 1057–1060 (2008). doi:10.1126/science.1156084 Medline

15. Y.-B. Ju, M. Koyama, T. Sawaguchi, K. Tsuzaki, H. Noguchi, In situ microscopic observations of low-cycle fatigue-crack propagation in high-Mn austenitic alloys with deformation-induced ε-martensitic transformation. Acta Mater. 112, 326–336 (2016). doi:10.1016/j.actamat.2016.04.042

http://dx.doi.org/10.1038/nmat812http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12612694&dopt=Abstracthttp://dx.doi.org/10.1038/178653a0http://dx.doi.org/10.1016/j.actamat.2012.10.029http://dx.doi.org/10.1016/j.ijfatigue.2006.11.015http://dx.doi.org/10.1038/nmat1351http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15778715&dopt=Abstracthttp://dx.doi.org/10.1016/j.actamat.2015.05.050http://dx.doi.org/10.1038/nmat1545http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16341218&dopt=Abstracthttp://dx.doi.org/10.1038/nmat832http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12612673&dopt=Abstracthttp://dx.doi.org/10.1016/j.pmatsci.2007.06.001http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=24434787&dopt=Abstracthttp://dx.doi.org/10.1038/srep22156http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=26907708&dopt=Abstracthttp://dx.doi.org/10.1126/science.1156084http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=18497294&dopt=Abstracthttp://dx.doi.org/10.1016/j.actamat.2016.04.042

16. B. Gludovatz, A. Hohenwarter, D. Catoor, E. H. Chang, E. P. George, R. O. Ritchie, A fracture-resistant high-entropy alloy for cryogenic applications. Science 345, 1153–1158 (2014). doi:10.1126/science.1254581 Medline

17. M. M. Wang, C. C. Tasan, D. Ponge, A. Kostka, D. Raabe, Smaller is less stable: Size effects on twinning vs. transformation of reverted austenite in TRIP-maraging steels. Acta Mater. 79, 268–281 (2014). doi:10.1016/j.actamat.2014.07.020

18. M. M. Wang, C. C. Tasan, D. Ponge, A. C. Dippel, D. Raabe, Nanolaminate transformation-induced plasticity–twinning-induced plasticity steel with dynamic strain partitioning and enhanced damage resistance. Acta Mater. 85, 216–228 (2015). doi:10.1016/j.actamat.2014.11.010

19. Materials and methods are available as supplementary materials.

20. J. A. Wasynczuk, R. O. Ritchie, G. Thomas, Effects of microstructure on fatigue crack growth in duplex ferrite-martensite steels. Mater. Sci. Eng. 62, 79–92 (1984). doi:10.1016/0025-5416(84)90269-6

21. Z. G. Hu, P. Zhu, J. Meng, Fatigue properties of transformation-induced plasticity and dual-phase steels for auto-body lightweight: Experiment, modeling and application. Mater. Des. 31, 2884–2890 (2010). doi:10.1016/j.matdes.2009.12.034

22. X.-L. Cai, J. Feng, W. S. Owen, The dependence of some tensile and fatigue properties of a dual-phase steel on its microstructure. Metall. Trans. A Phys. Metall. Mater. Sci. 16, 1405–1415 (1985). doi:10.1007/BF02658673

23. S. Suresh, R. O. Ritchie, Propagation of short fatigue cracks. Int. Met. Rev. 29, 445–475 (1984). doi:10.1179/imtr.1984.29.1.445

24. G. T. Gray, J. C. Williams, A. W. Thompson, Roughness-induced crack closure: An explanation for microstructurally sensitive fatigue crack growth. Metall. Trans. A Phys. Metall. Mater. Sci. 14, 421–433 (1983). doi:10.1007/BF02644220

25. R. O. Ritchie, Mechanisms of fatigue crack propagation in metals, ceramics and composites: Role of crack tip shielding. Mater. Sci. Eng. A 103, 15–28 (1988). doi:10.1016/0025-5416(88)90547-2

26. I. Verpoest, E. Aernoudt, A. Deruyttere, M. De Bondt, The fatigue threshold, surface condition and fatigue limit of steel wire. Int. J. Fatigue 7, 199–214 (1985). doi:10.1016/0142-1123(85)90051-9

27. M. A. Daeubler, A. W. Thompson, I. M. Bernstein, Influence of microstructure on fatigue behavior and surface fatigue crack growth of fully pearlitic steels. Metall. Trans. A Phys. Metall. Mater. Sci. 21, 925–933 (1990). doi:10.1007/BF02656577

28. H. R. Mayer, S. E. Stanzl-Tschegg, Y. Sawaki, M. Hühner, E. Hornbogen, Influence of transformation-induced crack closure on slow fatigue crack growth under variable amplitude loading. Fatigue Fract. Eng. Mater. Struct. 18, 935–948 (1995). doi:10.1111/j.1460-2695.1995.tb00918.x

http://dx.doi.org/10.1126/science.1254581http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=25190791&dopt=Abstracthttp://dx.doi.org/10.1016/j.actamat.2014.07.020http://dx.doi.org/10.1016/j.actamat.2014.11.010http://dx.doi.org/10.1016/0025-5416(84)90269-6http://dx.doi.org/10.1016/j.matdes.2009.12.034http://dx.doi.org/10.1007/BF02658673http://dx.doi.org/10.1179/imtr.1984.29.1.445http://dx.doi.org/10.1007/BF02644220http://dx.doi.org/10.1016/0025-5416(88)90547-2http://dx.doi.org/10.1016/0142-1123(85)90051-9http://dx.doi.org/10.1007/BF02656577http://dx.doi.org/10.1111/j.1460-2695.1995.tb00918.x

29. Z. Mei, J. W. Morris Jr., Analysis of transformation-induced crack closure. Eng. Fract. Mech. 39, 569–573 (1991). doi:10.1016/0013-7944(91)90068-C

30. A. G. Pineau, R. M. Pelloux, Influence of strain-induced martensitic transformations on fatigue crack growth rates in stainless steels. Metall. Trans. 5, 1103–1112 (1974). doi:10.1007/BF02644322

31. Y. Murakami, S. Kodama, S. Konuma, Quantitative evaluation of effects of non-metallic inclusions on fatigue strength of high strength steels. I: Basic fatigue mechanism and evaluation of correlation between the fatigue fracture stress and the size and location of non-metallic inclusions. Int. J. Fatigue 11, 291–298 (1989). doi:10.1016/0142-1123(89)90054-6

32. G. N. Haidemenopoulos, A. T. Kermanidis, C. Malliaros, H. H. Dickert, P. Kucharzyk, W. Bleck, On the effect of austenite stability on high cycle fatigue of TRIP 700 steel. Mater. Sci. Eng. A 573, 7–11 (2013). doi:10.1016/j.msea.2013.02.015

33. A. Aran, H. Türker, The effect of martensite content on the fatigue behaviour of a ferritic-martensitic steel. J. Mater. Sci. Lett. 9, 1407–1408 (1990). doi:10.1007/BF00721598

34. M. Abareshi, E. Emadoddin, Effect of retained austenite characteristics on fatigue behavior and tensile properties of transformation induced plasticity steel. Mater. Des. 32, 5099–5105 (2011). doi:10.1016/j.matdes.2011.06.018

35. G. T. Gray, A. W. Thompson, J. C. Williams, Influence of microstructure on fatigue crack initiation in fully pearlitic steels. Metall. Trans. A Phys. Metall. Mater. Sci. 16, 753–760 (1985). doi:10.1007/BF02814826

36. T. Fujisawa, S. Hamada, N. Koga, D. Sasaki, T. Tsuchiyama, N. Nakada, K. Takashima, M. Ueda, H. Noguchi, Proposal for an engineering definition of a fatigue crack initiation unit for evaluating the fatigue limit on the basis of crystallographic analysis of pearlitic steel. Int. J. Fract. 185, 17–29 (2014). doi:10.1007/s10704-013-9895-3

37. M.-M. Wang, C. C. Tasan, D. Ponge, D. Raabe, Spectral TRIP enables ductile 1.1 GPa martensite. Acta Mater. 111, 262–272 (2016). doi:10.1016/j.actamat.2016.03.070

38. S. Hamada, T. Fujisawa, M. Koyama, N. Koga, N. Nakada, T. Tsuchiyama, M. Ueda, H. Noguchi, Strain mapping with high spatial resolution across a wide observation range by digital image correlation on plastic replicas. Mater. Charact. 98, 140–146 (2014). doi:10.1016/j.matchar.2014.10.010

39. M. Ohnami, Fracture and Society (IOS Press, 1992).

40. D. C. R. Waryoba, J. S. Mshana, Effect of size and stress gradient on fatigue behavior. Int. J. Pressure Vessels Piping 60, 177–182 (1994). doi:10.1016/0308-0161(94)90024-8

41. T. Araki, NRIM Fatigue Data Sheet No. 2 (National Research Institute for Metals, 1978).

42. T. Araki, NRIM Fatigue Data Sheet No. 3 (National Research Institute for Metals, 1978).

43. T. Araki, NRIM Fatigue Data Sheet No. 4 (National Research Institute for Metals, 1978).

http://dx.doi.org/10.1016/0013-7944(91)90068-Chttp://dx.doi.org/10.1007/BF02644322http://dx.doi.org/10.1016/0142-1123(89)90054-6http://dx.doi.org/10.1016/j.msea.2013.02.015http://dx.doi.org/10.1007/BF00721598http://dx.doi.org/10.1016/j.matdes.2011.06.018http://dx.doi.org/10.1007/BF02814826http://dx.doi.org/10.1007/s10704-013-9895-3http://dx.doi.org/10.1016/j.actamat.2016.03.070http://dx.doi.org/10.1016/j.matchar.2014.10.010http://dx.doi.org/10.1016/0308-0161(94)90024-8

44. S. Nishijima, Fundamental Fatigue Properties of JIS Steels for Machine Structural Use. NRIM Fatigue Data Sheet Technical Document No. 5 (National Research Institute for Metals, 1981).

45. N. Hattori, S. Nishida, A. Takahashi, Effect of structure stability on fatigue properties of austenite stainless steels. Trans. Jpn. Soc. Mech. Eng. A 65, 340–344 (1999). doi:10.1299/kikaia.65.340

46. L. Wagner, Mechanical surface treatments on titanium, aluminum and magnesium alloys. Mater. Sci. Eng. A 263, 210–216 (1999). doi:10.1016/S0921-5093(98)01168-X

http://dx.doi.org/10.1299/kikaia.65.340http://dx.doi.org/10.1016/S0921-5093(98)01168-X

aal2766-Koyama-SM.ref-list.pdfReferences and Notes