Effects of oxides nanoparticles on the microstructure and properties of Mo composites prepared via SPS sintering

Abstract

Simultaneous achieving the second-phase particle strengthening, high density, and fine grain is a great difficulty for designing and preparing Mo alloys. In this study, the effects of γ-Al2O3 and Y2O3 nanoparticles on the microstructures and properties of Mo composites prepared via spark plasma sintering (SPS) were systematically investigated. It was found that for pure Mo and Mo–Y2O3 powders, Mo compact with both high density and fine grain size can't be achieved. However, Mo-Al2O3 composite with both a relatively high density (98%) and a fine grain size (1.67 μm) was synthesized successfully. The small γ-Al2O3 particles transformed into larger κ-Al2O3 particles by obvious grain boundary migration and grain growth in the sintering process, which effectively pinned the migration of Mo grain boundary with few effects on the surface atom diffusion of Mo. Moreover, there was a crystallographic orientation relationship between the κ-Al2O3 particles and Mo matrix (Mo (110)//Al2O3 (134‾1)). Ultrafine Mo composite containing dispersed Al2O3 particles with stable boundary adhesion can efficiently hinder dislocation movement and crack propagation, resulting in the obvious enhancements of bending strength, hardness and compressive yield strength.