Mechanism of enhanced room temperature ductility of cold–rolled tungsten under micro-bending test

Abstract

The enhanced ductility of cold-rolled (CR) tungsten at room temperature is considered to be related to the activities of dislocations and the associated microstructures. However, the specific mechanism and the exact roles that dislocation activity and microstructure effects play in enhancing ductility in CR tungsten are still subjects of conjecture. In this context, three-dimensional electron backscatter diffraction reveals that a CR tungsten micro-cantilever fractures in a semi-brittle manner within the L-T fracture system. The ductile, blunted region shows high dislocation mobility away from the cracking tip, and its emission pathway is strongly correlated with low-angle grain boundaries. Meanwhile, strain and dislocations blocked at high-angle grain boundaries induces stress cracking and results in brittle intergranular fracture. These ductile and brittle failure modes trigger the crack bridging effect, ultimately leading to controlled crack propagation. This work would provide valuable idea for future investigations into the ductility enhancement of ultra-fine grain W.