Effects of strain aging on the structure and mechanical properties of PM 92·5W–5Ni–2·5Fe heavy alloys

Abstract

This paper describes the effects of strain aging on the mechanical properties and the microstructure of forged 92·5W–5Ni–2·5Fe and its heavy alloys microalloyed with cobalt. The investigation was performed on cold rotary forged rods deformed 15, 20 and 30% and strain aged at temperatures from 673 to 1273 K for 1·8–32·4 ks. The results show that for these alloys, there is a temperature range from 773 to 873 K in which maximum ultimate strength and hardness can be attained. Furthermore, the strain aged alloys have shown strength and hardness increase at a temperature of 973 K in a time period of 10·8 ks. The fracture analysis has shown the presence of predominant transgranular fracture of the tungsten phase and γ-phase in the strain-aged alloys in comparison with the forged alloys. The results indicate that interface and tungsten phase strengthening are predominant mechanisms of strain aging.

Keywords:

• HEAVY METAL
• POWDER METALLURGY
• STRAIN AGING
• MECHANICAL AND STRUCTURAL PROPERTIES
• FRACTURE ANALYSIS