TY - JOUR

T1 - Plastic deformation of NiTi shape memory alloys

AU - Ezaz, Tawhid

AU - Wang, J.

AU - Sehitoglu, Huseyin

AU - Maier, H. J.

N1 - Funding information: The work is supported by the National Science Foundation under DMR-0803270. The authors gratefully acknowledge the use of the parallel computing resources part of the Taub cluster provided by the Computational Science and Engineering Program at the University of Illinois, partial support from CMMI-09-26813 and CRDF Award RUE1-2983-TO-10. The assistance of Wael Abuzaid with the pseudoelasticity experiments is acknowledged.

PY - 2012/10/26

Y1 - 2012/10/26

N2 - Dislocation slip in B2 NiTi is studied with atomistic simulations in conjunction with transmission electron microscopy (TEM). The atomistic simulations examine the generalized stacking fault energy (GSFE) curves for the {0 1 1}, {2̄11} and {0 0 1} planes. The slip directions considered are 〈1 0 0〉, 〈1 1 1〉 and 〈0 1 1〉. The results show the smallest energy barriers for the (0 1 1)[1 0 0] case, which is consistent with the experimental observations of dislocation slip reported in this study. To our knowledge, slip on the (0 1 1)[11̄1] system is illustrated for the first time in our TEM findings, and atomistic simulations confirm that this system has the second lowest energy barrier. Specimens that underwent thermal cycling and pseudoelasticity show dislocation slip primarily in the austenite domains while the bulk of martensite domains does not display dislocations. The results are discussed via calculation of the ideal slip nucleation stress levels for the five potential slip systems in austenite.

AB - Dislocation slip in B2 NiTi is studied with atomistic simulations in conjunction with transmission electron microscopy (TEM). The atomistic simulations examine the generalized stacking fault energy (GSFE) curves for the {0 1 1}, {2̄11} and {0 0 1} planes. The slip directions considered are 〈1 0 0〉, 〈1 1 1〉 and 〈0 1 1〉. The results show the smallest energy barriers for the (0 1 1)[1 0 0] case, which is consistent with the experimental observations of dislocation slip reported in this study. To our knowledge, slip on the (0 1 1)[11̄1] system is illustrated for the first time in our TEM findings, and atomistic simulations confirm that this system has the second lowest energy barrier. Specimens that underwent thermal cycling and pseudoelasticity show dislocation slip primarily in the austenite domains while the bulk of martensite domains does not display dislocations. The results are discussed via calculation of the ideal slip nucleation stress levels for the five potential slip systems in austenite.

KW - Density functional theory

KW - Dislocations

KW - NiTi

KW - Shape memory

KW - Slip

UR - http://www.scopus.com/inward/record.url?scp=84869081787&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2012.09.023

DO - 10.1016/j.actamat.2012.09.023

M3 - Article

AN - SCOPUS:84869081787

VL - 61

SP - 67

EP - 78

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 1

ER -