Investigation of deformation and heat treatment effects on properties of PM 92.5W-5Ni-2.5Fe heavy alloys

This paper presents the effects of vacuum heat treatment under different cooling conditions on mechanical and structural properties of forged heavy alloys, such as 92.5W-5Ni-2.5Fe and 92.5W-5Ni-25Fe microalloyed with Co. The tungsten composition in the c phase has proved to be higher and more homogenous in the rapidly cooled alloys than in the slowly cooled ones. The effects of chemical composition inhomogeneity on mechanical and structural properties of alloys were also analysed and discussed. The results of tensile and toughness testing have shown an increase in ductility and toughness, while the strength of heat treated alloys decreased in comparison with the strength of forged alloys. The fracture analysis has shown that in the sintered and rotary forged alloys, intergranular fracture of the tungsten phase and transgranular fracture of the γ phase occurred, respectively. The fracture of these phases after heat treatment was characterised by transgranular morphology.