Evolution of tension twinning in single crystal Ti under compressive uniaxial strain conditions

S Rawat and N Mitra, COMPUTATIONAL MATERIALS SCIENCE, 141, 302-312 (2018).

DOI: 10.1016/j.commatsci.2017.09.041

We perform molecular dynamics simulations to study the evolution of tension twinning in single crystal Ti under uniaxial strain conditions. The objective is to understand the evolution trends of twin volume fraction as well as number of twins and express them in terms of the individual twin dynamics. The compressive strain applied along < 2 (1) over bar (1) over bar 0 > and < 0 1 (1) over bar 0 > directions leads to the activation of 1 0 (1) over bar 2 twin variants. We find that the activation of twin variants follows the Schmid criterion. However, they do not activate at the same time even with equal Schmid factor indicating the stochastic nature of the twin variant activation. For the case where four variants activate (loading along < 2 (1) over bar (1) over bar 0 > direction), high nucleation events occur compared to the case where only two variants activate (loading along < 0 1 (1) over bar 0 > direction). The activated variants in each case do not evolve with same rate even with equal Schmid factor and a clear dominance of twin variants is observed. For the case where only two variants activate, average twin growth rate and overall twin volume fraction are high compared to the case where four variants activate. A correlation between the number of activated variants and the overall twin volume fraction is observed. The size distribution of the nucleated twins follows the power law function. The expressions provided for overall number of twins and overall twin volume fraction can serve as a basis to develop the physicsbased twin evolution laws to model twinning at higher length scales. (C) 2017 Elsevier B.V. All rights reserved.

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