Microstructural and mechanical analysis of single crystal iron under non-planar loading: Atomic simulation

Abstract

Current research still lacks understanding of the microstructure evolution and mechanical response of iron under non-planar loading conditions. In this work, the molecular dynamics simulation is used to investigate the effects of non-planar loading on single crystal iron with different loading directions, focusing on the microstructure evolution, the related mechanical characteristics, and the morphology evolution. For non-planar loading along different directions, different glide planes will be activated, leading to plastic deformation, which can be divided into two types: In the first type, dislocations glide occurs initially, followed by phase transformation between the glide planes. In the second type, phase transformation nucleation occurs first, followed by the formation of twins or dislocations in the phase transformation region. The products of phase transformation include abundant HCP and FCC phases, forming mixed- phase structures. The morphology of the iron after non-planar loading is affected by its microstructural evolution, exiting the obvious anisotropy of the hardness. Loading along the z[011]–x[100] direction has the shallowest penetration depth because a largest number of dislocations are formed. Meanwhile, temperature rise caused by structural deformation will also affect the hardness of materials through temperature softening effect. For loading along the z[111]–x[112¯] direction, the iron occurs the asymmetric structure deformation, leading to asymmetric stress and temperature distribution, as well as asymmetric fragmentation and jetting phenomenon. In addition, the composition of jetting is different under different loading directions. Among them, the flyer in the jetting material has the highest content when loading along the z[001]–x[100] direction.