Computational study of nanoscale mechanical properties of Fe–Cr–Ni alloy

Mechanical properties of Fe–Cr–Ni alloy nanowires have been investigated using molecular dynamics simulation with embedded atom method and first principles approach. Various cases of uniaxial tension, compression and shear deformations have been performed and studied in this work. From the first principles calculations, the higher magnitudes of uniaxial and shear deformations resulted in higher probability of martensitic transformations. Before the first yielding, nanowires preserved the elastic stage and then the mechanical deformation proceeded in alternating quasi-elastic and yielding stages. The plastic behaviour was not observed in compression while both tensile and shear deformations showed apparent plastic behaviour. In shear deformation, due to the martensitic phase transformation, the plastic behaviour persisted for total strain of 0.6 which was much larger than that during tensile and compression. This validated the previous experimental observations. In the studied Fe–Cr–Ni nanowires, deformations were controlled by dislocations. Dislocation-mediated twinnings were captured by common neighbour analysis. Twin quantification showed that the twin activity increased with increasing strain rate. Twinnings originated from stacking faults led by 1/6 <112> Shockley partial dislocations. At elevated temperature (beyond 500 K), the materials softening happened, and 316L nanowire became more plastic under a lower stress.