Effect of thermomechanical processing via rotary swaging on properties and residual stress within tungsten heavy alloy

Abstract

The effects of cold and warm rotary swaging and subsequent post-process annealing on mechanical properties, residual stress, and structure development within WNiCo powder-based pseudo-alloy were predicted numerically and investigated experimentally. The swaging temperature of 900 degrees C imparted increase in the Young's and shear moduli; the post-process annealing at 900 degrees C also imparted decrease in the residual stress values, primarily due to structure recovery introduced within the matrix. Cold rotary swaging at 20 degrees C imparted ultimate tensile strength of almost 1 900 MPa, while warm rotary swaging at 900 degrees C introduced increased plasticity (almost 24 % after a single swaging pass). Post-process heat treatment promoted diffusion of W to the Ni/Co matrix, which increased strength, but remarkably decreased elongation to failure and residual stress. Numerically predicted results of mechanical behaviour corresponded to the experimental results and confirmed the favourable effects of the selected thermomechanical treatments on WNiCo performance.