The austenite/lath martensite interface in steels: Structure, athermal motion, and in-situ transformation strain revealed by simulation and theory

Maresca, Francesco; Curtin, W.A.

doi:10.1016/j.actamat.2017.05.044

Cited by 72 publications

(67 citation statements)

References 66 publications

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“…of the SFE is negative both from the Meyer-Entel potential and first principles data, which indicates a spontaneous formation of the planar defects in the fcc phase. The SFE of the modified embedded atom method (MEAM) type potential by Lee et al for the fcc phase was found to be positive (+37.5 mJ/m 2 ) in opposite trend to the first principles data [31,32], therefore we do not use this potential. For the present work, it is very important to have the correct energetics of the planar defects, in this case SF, with respect to the first principles data; because it is this energetics that controls the stability of the planar defects in the fcc phase.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Effect of pre-existing defects in the parent fcc phase on atomistic mechanisms during the martensitic transformation in pure Fe: A molecular dynamics study

2018

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Molecular dynamics (MD) simulations are used to study the effect of different defect configurations and their arrangements in the parent fcc phase on atomistic mechanisms during the martensitic transformation mechanisms in pure Fe. The defect configurations considered are stacking faults (SF) and twin boundaries (TB) in single crystal fcc. Three arrangements of these defect structures are considered: parallel TB, intersecting SF, and intersecting SF and TB. Each of these defect configurations affects the transformation mechanisms and transformation temperatures. Parallel TB are the lowest-barrier sites for the atomic shear and thus accelerate the transformation process. The fcc phase with parallel TB follows the Nishiyama-Wasserman (NW) martensitic transformation mechanism. On the other hand, intersecting SF impede the atomic shear and thus retard the transformation. The atomistic transformation mechanism in this case first follows the hcp to bcc Burgers path and then the fcc to bcc Olson-Cohen model. The intersecting SF and TB result in a combined effect of both the previous cases. The simulation results show the occurrence of different atomistic mechanisms during martensitic transformation depending on the type of defects present in the parent fcc phase.

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Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Effect of pre-existing defects in the parent fcc phase on atomistic mechanisms during the martensitic transformation in pure Fe: A molecular dynamics study

2018

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“…Molecular dynamics (MD) simulation has contributed to the atomistic analysis of the processes occurring under the transformation, and several characteristics-such as the transformation pathway or the kinetics of the transformation-could be successfully analyzed [4][5][6]. Besides the thermally induced transformation, the effect of applied stresses was also studied [7][8][9][10], to analyze how and to what extent such stresses may trigger and influence the transformation.…”

Section: Introductionmentioning

confidence: 99%

Dislocations Help Initiate the α–γ Phase Transformation in Iron—An Atomistic Study

Meiser

Urbassek

2019

Metals

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Using molecular dynamics simulation, we studied the influence of pre-existing dislocations on the austenitic and the martensitic phase transformations in pure iron. The simulations were performed in a thin-film geometry with (100) surfaces. We found that dislocations alleviate the transformation by lowering the austenitic transformation temperature and increasing the martensitic transformation temperature. In all cases, the new phase nucleates at the dislocations. The orientation relationships governing the nucleation process are dominated by the Burgers, Kurdjumov–Sachs, and Nishiyama–Wassermann pathways. However, upon growth and coalescence of the transformed material, the final microstructure consists of only few twinned variants separated by twin boundaries; this simple structure is dictated by the free surfaces which tend to form conserved planes under the transformation. After transformation, the material also contains abundant dislocations.

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“…Thus, it has been found that grain boundaries [5,6], other planar defects such as stacking faults [7] and dislocations [8][9][10] may act as nucleation sites for the transformation. In addition, phase boundaries [11][12][13][14] and heterogeneous interfaces, such as with carbide phases [15], affect the transformation behavior; in these cases, of course, the crystal orientation at the interface is decisive.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Crystal Surface on the Austenitic and Martensitic Phase Transition in Pure Iron

Meiser

Urbassek

2018

Crystals

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Using classical molecular dynamics simulations, we studied the influence that free surfaces exert on the austenitic and martensitic phase transition in iron. For several single-indexed surfaces—such as ( 100 ) bcc and ( 110 ) bcc as well as ( 100 ) fcc and ( 110 ) fcc surfaces—appropriate pathways exist that allow for the transformation of the surface structure. These are the Bain, Mao, Pitsch, and Kurdjumov–Sachs pathways, respectively. Tilted surfaces follow the pathway of the neighboring single-indexed plane. The austenitic transformation temperature follows the dependence of the specific surface energy of the native bcc phase; here, the new phase nucleates at the surface. In contrast, the martensitic transformation temperature steadily decreases when tilting the surface from the (100) fcc to the (110) fcc orientation. This dependence is caused by the strong out-of-plane deformation that (110) fcc facets experience under the transformation; here, the new phase also nucleates in the bulk rather than at the surface.

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The austenite/lath martensite interface in steels: Structure, athermal motion, and in-situ transformation strain revealed by simulation and theory

Cited by 72 publications

References 66 publications

Effect of pre-existing defects in the parent fcc phase on atomistic mechanisms during the martensitic transformation in pure Fe: A molecular dynamics study

Effect of pre-existing defects in the parent fcc phase on atomistic mechanisms during the martensitic transformation in pure Fe: A molecular dynamics study

Dislocations Help Initiate the α–γ Phase Transformation in Iron—An Atomistic Study

Influence of the Crystal Surface on the Austenitic and Martensitic Phase Transition in Pure Iron

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