Effect of swaging and aging heat treatment on microstructure and mechanical properties of tungsten heavy alloy

Abstract

In the present study, a 90W-6Ni-2Fe-2Co (Wt.%) tungsten heavy alloy was processed through liquid phase sintering route, followed by vacuum heat treatment and swaging. Further, ageing was carried out at 700° C for three different time period, in order to improve mechanical properties. Microstructural analysis showed decrease in contiguity levels from sintered to swaged condition. Swaging improved the tensile strength of the alloy at the expense of ductility and impact. Aging of the swaged alloys showed further improvement in yield, tensile strength and hardness of the alloy with concomitant loss of ductility and impact toughness. The fracture surface of sintered alloy exhibited brittle failure features consisting of tungsten-matrix and tungsten-tungsten failure. However, the heat treated alloy showed lesser intergranular failure indicating higher ductility. The swaged alloy exhibited relatively higher fraction of transgranular cleavage features. The study shows that the heat treatment (that includes solution heat treatment and ageing) and swaging can be used judiciously to tailor the final mechanical properties of the tungsten heavy alloys.