Compression twinning and structural phase transformation of single crystal titanium under uniaxial compressive strain conditions: Comparison of inter-atomic potentials

S Rawat and N Mitra, COMPUTATIONAL MATERIALS SCIENCE, 126, 228-237 (2017).

DOI: 10.1016/j.commatsci.2016.09.034

We perform molecular dynamics simulations to simulate the c-axis compression of single crystal Ti at high strain rates under uniaxial strain conditions. Since it is well known that molecular dynamics simulations heavily rely upon the type of potential used, a comprehensive study is presented in which four different commonly utilized potentials for Ti (Ackland, Mishin, Kim and Hennig) are evaluated against their abilities to demonstrate different variants of compression twins, dislocation structures and structural phase transformation. We find that 10 (1) over bar1 and 11 (2) over bar2 twins activate for Ackland and Mishin potentials, while only 10 (1) over bar1 twins activate for Kim potential. No compression twin systems activate for Hennig potential. The c-vector analysis of unknown structure generated with Ackland, Mishin and Kim potentials shows that the unknown structure has 10 (1) over bar1 twin-like orientations and the structure factor analysis gives a signature of pressure-induced omega phase for the twin-like oriented unknown structure. No signature of twin-like oriented unknown structure and omega phase is observed for Hennig potential. The large amount of dislocation density is observed for Ackland potential followed by Mishin, Kim and Hennig potentials. The presence of compression twins and high dislocation density for Ackland, Mishin and Kim potentials suggest that the c-axis deformation is accommodated by twins and slip together, while only slip accommodates the c-axis deformation for Hennig potential. Based on these observations and as well as on the formulation of the above mentioned potentials, Kim potential is being recommended for use under c-axis uniaxial compressive strain loading situations. (C) 2016 Elsevier B.V. All rights reserved.

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