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

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 { 1 0 1 ¯ 1 } and { 1 1 2 ¯ 2 } twins activate for Ackland and Mishin potentials, while only { 1 0 1 ¯ 1 } 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 { 1 0 1 ¯ 1 } twin-like orientations and the structure factor analysis gives a signature of pressure-induced ω phase for the twin-like oriented unknown structure. No signature of twin-like oriented unknown structure and ω 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.