Effect of High-Energy Ball Milling Time on the Density and Mechanical Properties of W-7%Ni-3%Fe Alloy

The present work was aimed at the investigation of the effect of high-energy ball milling (HEBM) time on the sintering kinetics, structure, and properties of the heavy tungsten alloy (HTA) W-7%Ni-3%Fe. The HTA samples were obtained from nanopowders (20-80 nm) using conventional liquid-phase sintering (LPS) in hydrogen and using spark plasma sintering (SPS) in vacuum. The HTA density was shown to depend non-monotonously on the HEBM time that originates from the formation of nonequilibrium solid solutions in the W-Ni-Fe systems during HEBM. The SPS kinetics of the HTA nanopowders was shown to have a two-stage character, the intensity of which depends on the Coble diffusion creep rate and on the intensity of diffusion of the tungsten atoms in the crystal lattice of the gamma-phase. The kinetics of sintering of the initial submicron powders has a single-stage character originating from the intensity of the grain boundary diffusion in the gamma-phase. The dependencies of the hardness and of the yield strength on the grain sizes were found to obey the Hall-Petch relation. The hardness, strength, and dynamic strength in the compression tests of the fine-grained tungsten alloys obtained using SPS and LPS were studied.