Stereographical and characterization analysis of nano yttria-dispersed tungsten heavy alloys: Impact on particle size and Y-W-O complex oxide formation

The present study investigates the influence of nano-Y2O3 (0.25-0.75 wt%) additions on the microstructural evolution of a tungsten heavy alloy (WHA) composed of 93 wt% tungsten, with a fixed Ni/Co binder ratio of 9. The precursor powders of Ni, Co, and Y2O3 were subjected to high-energy ball milling to produce an oxide-dispersion-strengthened (ODS) matrix, which was subsequently blended with tungsten via low-energy ball milling. The resulting composite powders were consolidated through cold isostatic pressing and sintered at 1438 degrees C for 1 h. The processed ODS-W-Ni-Co alloys achieved a relative density exceeding 99.7 % of the theoretical value. Microstructural analysis confirmed the formation of a W-Y-O complex oxide phase, characterized by core-shell structures and particle coarsening phenomena. These structural transformations substantially influenced grain morphology, growth kinetics, and overall microstructural refinement. Notably, the incorporation of 0.75 wt% Y2O3 increased the solid-liquid interfacial energy to 744.44 MJ/m2, albeit inducing anisotropic interfacial energy distributions. High-resolution transmission electron microscopy (HR-TEM) revealed a semi-coherent gamma-Ni/Y2O3 interface with a lattice mismatch parameter of 0.056, which is indicative of enhanced interfacial bonding. The presence of this semi-coherent interface is proposed to improve interfacial strengthening between W grains and the gamma-Ni binder phase, contributing to microstructural stability and potential mechanical property enhancement.