A comparative investigation of shock response in high entropy Cantor alloys by MEAM and LJ type potentials

Abstract

We assess the effect of interatomic potential in determining the shock response of the high entropy Cantor alloy through large scale non-equilibrium molecular dynamics simulations. In literature, two different potentials have been suggested for modelling Cantor alloys at atomic scale – the 2NN MEAM potential, henceforth termed as the MEAM potential, and the Lennard-Jones (LJ) type-potential. We show that the MEAM potential results in a different shock response than the LJ type-potential – (i) the shock wave speed and the pressure behind the shock front are smaller for MEAM than the LJ type-potential, (ii) no twinning is observed with the MEAM potential along the [100] direction unlike that with the LJ type-potential, and (iii) the shock induced phase transition from FCC to HCP is observed along the [100] direction only with the LJ type-potential. Our numerical results with the LJ type-potential are in agreement with the experiments as well, where twinning and phase transition have been observed. Looking at the morphology of the post-shocked samples at different times, we identify the mechanism behind the phase transition. Lastly, we subject the post-shocked structure to uniaxial tensile tests to show that for the [111] direction, a greater fracture strain than the unshocked structure is obtained, suggesting a higher fracture toughness. • Used 2-NN MEAM and LJ-type potential to study the effect of shock loading in Cantor alloy. • The LJ-type potential results in higher shock pressure and shock speed as compared to MEAM. • The elastic precursor wave is overdriven by the plastic wave along [100], unlike the [110] and [111] directions. • Plastic deformation by slipping and twinning in [100] direction is observed with LJ-type, consistent with experiments, unlike the MEAM potential. • Disordered phases along [110] and [111] directions increases the fracture toughness in after-shocked samples.