Molecular dynamics investigation of c-axis deformation of single crystal Ti under uniaxial stress conditions: Evolution of compression twinning and dislocations

Abstract

Twinning plays an important role on the microstructure evolution of HCP metals. In this work, we perform c-axis compression of single crystal Ti under uniaxial stress conditions using molecular dynamics simulations. The objective is to demonstrate activation and evolution of compression twins along with dislocations when Ti single crystals are loaded in uniaxial stress conditions using two commonly utilized interatomic potentials. We find that activation of only {101¯1} compression twins with the Kim potential is inconsistent with the Schmid criterion while activation of both {101¯1} and {112¯2} compression twins with the Hennig potential is consistent with the Schmid criterion. Twin variants activated do not contribute equally to the total twinned volume even with equal Schmid factor for both potentials and thereby demonstrating inability of the Schmid criterion to predict dominance and evolution of twin variants. The Kim potential shows large amount of dislocation density in comparison to the Hennig potential. The strain rate sensitivity on activation of compression twin systems is observed with the Hennig potential. The study can be utilized to further investigate the evolution of compression twins required to develop/improve twin volume fraction evolution laws for crystal plasticity finite element simulations.