PNNL

Abstract

A promising approach to increasing fracture toughness and decreasing the DBTT of a W-alloy is by ductile-phase toughening (DPT). In this method, a ductile phase is included in a brittle matrix to prevent fracture propagation by crack bridging or crack deflection. Liquid-phase sintered W-Ni-Fe alloys consisting of nearly spherical W-particles embedded within a Ni-Fe-W ductile matrix are being manipulated by hot-rolling to create lamellar W/Fe-Ni-W composites with anisotropic fracture properties. The rolled W-Ni-Fe alloy becomes a lamellar alloy consisting of W lamellae separated by ductile-phase regions. The W-rich lamellae are strong but brittle, while the ductile-phase metallic regions have a thin, plate-like morphology to provide a ductile bridging region. This rolled material is oriented with the W-rich lamellae parallel to principal stresses so that surface cracking is normal to the ductile-phase bridging regions.