Dislocation Substructures in Hot-deformed Ni-based Alloys: Simulation for Structure Evolution of Hot-worked Austenite in Low Carbon Steels

Abstract

The dislocation substructure in compressively deformed fcc 70Ni-30Fe and 67Ni-30Fe-3Ti alloys was investigated to understand or model microstructural evolution in austenite of low carbon steels during hot deformation. These Ni-based alloys are expected to show similar deformation characteristics to austenitic steels because of similar stacking fault energy. The deformation substructure depended in particular on deformation temperature. Below 700°C a heavy deformation (70% reduction) introduced microbands, while above 800°C it produced equiaxed dislocation cell structures with some partially recrystallized austenite grains. Crystallographic misorientation in microband structures tended to be larger than that in cell structures at the fixed strain and temperature. Preexisting precipitates effectively suppressed the growth of austenite grains recrystallized after deformation, which resulted in macroscopically homogeneous dislocation substructures consisting of microbands. The temperature dependence of dislocation substructures may closely relate to the mechanism of diffusional transformation to ferrite at very low temperature 500°C through strain assisted transformation in low carbon steels.