TY - JOUR

T1 - Energetics of (1 1 4) twinning in B2 NiTi under coupled shear and shuffle

AU - Ezaz, Tawhid

AU - Sehitoglu, Huseyin

AU - Maier, Hans Jürgen

N1 - Funding information: The work is supported by the National Science Foundation under DMR-0803270. We acknowledge earlier discussions with Prof. D.D. Johnson on PES. 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, and also partial support from CMMI-1130031.

PY - 2011/11/4

Y1 - 2011/11/4

N2 - The (1 1 4) twin growth in the austenitic regime in NiTi (B2 lattice) is characterized precisely at the atomistic scale. This twinning mode is consistent with experimental observations but has not been well understood despite its importance. Combined shears, shuffles and interface shifts operate in a complex way to generate the (1 1 4) twin. Pure shear on the (1 1 4) plane results in a "pseudo-twin", and interchange shuffles are necessary to convert this to a "reflective" twin and render a lower energy state. Additional atomic shifts at the twin-matrix interfaces result in "sharp" boundaries, further lowering the energy barriers. We established the energy barrier to be 148 mJ m-2 during (114)[221̄] twin boundary growth of four layers at a time. The entire potential energy surface and the mean energy path during twinning can be derived from our simulations, providing the required insight into the atomistic processes involved.

AB - The (1 1 4) twin growth in the austenitic regime in NiTi (B2 lattice) is characterized precisely at the atomistic scale. This twinning mode is consistent with experimental observations but has not been well understood despite its importance. Combined shears, shuffles and interface shifts operate in a complex way to generate the (1 1 4) twin. Pure shear on the (1 1 4) plane results in a "pseudo-twin", and interchange shuffles are necessary to convert this to a "reflective" twin and render a lower energy state. Additional atomic shifts at the twin-matrix interfaces result in "sharp" boundaries, further lowering the energy barriers. We established the energy barrier to be 148 mJ m-2 during (114)[221̄] twin boundary growth of four layers at a time. The entire potential energy surface and the mean energy path during twinning can be derived from our simulations, providing the required insight into the atomistic processes involved.

KW - (1 1 4) shuffle

KW - ab initio

KW - B2 NiTi

KW - Deformation twinning

UR - http://www.scopus.com/inward/record.url?scp=80155211129&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2011.09.032

DO - 10.1016/j.actamat.2011.09.032

M3 - Article

AN - SCOPUS:80155211129

VL - 60

SP - 339

EP - 348

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 1

ER -