The orientation spreading in γ-fiber of electron beam melted Ta-2.5W alloy during cold rolling

The work presents a detailed investigation of the microstructure characteristics of the γ-fiber (normal direction//<111>) in electron beam melted Ta-2.5W alloy subjected to cold rolling. With increasing strain, the average space of microbands decreases towards a saturation value which is about 0.5 μm. The typical microstructure in γ fiber is microbands and shear bands in different appearance. The microbands are relatively straight and aligned close with slip planes when the strain is lower than 60%. The non-crystallographic irregular microbands and shear bands prevail in γ fiber when the strain is larger than 70%. When the strain reaches 90%, a group of parallel macroshear bands are formed. The orientation of γ fiber can spread up to 60°. Both {111}<112> and {001}<120> new orientations are developed in {111}<110> orientation. Many new developed high angle boundaries of these new grains are coincident site lattice boundaries (Σ3 and Σ9). Meanwhile, these new grains and matrix always share a common <111> or <110> with matrix.