The evolution of shear bands in Ta-2.5W alloy during cold rolling

Abstract

The characteristics of shear bands in cold-rolled Ta-2.5W alloy are systematically investigated at different mechanical reduction levels. With increasing strain, the shear bands can appear as in-grain shear bands, trans-granular shear bands and wavy bands. At low strain the crystallographic planar in-grain shear bands are aligned close to the highly stressed slip planes at low strain. As strain increases, the shear bands rotate around the <110> or <111> direction to smaller inclination angles with respect to the rolling direction (RD). Meanwhile, new groups of shear bands are developed. Two groups of in-grain shear bands with a specific fishbone structure appear in the orientations with larger Taylor factor at medium strain. The trans-granular shear bands are formed when the adjacent grains get the continuity of slip planes. Therefore, the frequency of trans-granular shear bands increases with the enhancing of local texture. The wavy bands appear to be a result of sequential necking in the harder γ-fiber and a cooperative flow in the softer α-fiber. Meanwhile, the formation model of the wavy bands is also proposed based on the laminar composites.