On the flow and work hardening behavior of tungsten heavy alloy 92W-5.5Ni-2.5Fe

Abstract

Present work describes flow and work hardening behavior of Tungsten Heavy Alloy 92W-5.5Ni-2.5Fe (wt%) in heat treated and swaged conditions. The morphology of W-grains in heat treated and swaged materials is equiaxed and elongated in longitudinal direction with same volume fraction, respectively. The swaged material depicts different contiguity values along transverse and longitudinal directions. The strength and elongation values in heat treated condition are smaller and larger than those of the swaged material. The difference in σYS and σUTS values is very small in swaged material. The true stress-true plastic strain curve of the alloy on log-log scale exhibits two slopes in heat treated condition and follows Ludwigson constitutive equation. This can be attributed to the differences in micro hardness values of W-grains and matrix phase. In contrast, the true stress-true plastic strain curve of the swaged alloy on log-log scale displays only single slope and follows Swift equation due to the presence of pre-strain in the material. Both the materials exhibit three typical stages (I, II and III) of work hardening and linear part of stage III follows KME model. The fracture surface of heat treated material consists of W-cleavage, W-W decohesion and matrix rupture in considerable proportions. In contrast, the swaged material displays the presence of mainly W-cleavage. The fraction of W-matrix failure is significantly small and more or less same in both the materials.