The evolution of deformation microstructure in electron beam melted Ta-2.5W alloy during cold rolling

The evolution of deformation microstructure in electron beam melted Ta-2.5W alloy was investigated. The morphology of microbands appear different in different reduction levels. The microbands are relatively straight at low to medium strain and can cross the grain boundary. They become wavy when the reduction reaches 70%. The microbands are parallel with rolling direction when the reduction is up to 90%. The average inclination angles between microbands and rolling direction is about 35° at 20% reduction and get smaller and smaller with increasing strain. EPBs are developed when the reduction is 20%. Most of grains contain one or two groups of EPBs occupying almost the whole grain interiors when the reduction is larger than 30%. The EPBs are fragmented, diffused and curved in the early stages of development. When the reduction reaches 40%, the EPBs become more well-developed and homogeneous. The dislocations within EPBs tend to rearrange themselves with increasing strain in a sequence, from tangled dislocations, followed by parallel dislocations and finally into dislocation nets. The evolution of microbands is related with both the cross-slip of dislocations and the splitting of high dense dislocation walls.