A study on the effect of solution acidity on the microstructure, mechanical, and wear properties of tungsten alloys reinforced by yttria-stabilised zirconia particles

Abstract

Solution acidity greatly affects the fabrication of high-performance oxide dispersion-strengthened tungsten (ODS-W) alloys by liquid-liquid doping. In the present study, yttria-stabilised zirconia (Zr(Y)O2)-strengthened tungsten alloys (W-Zr(Y)O2) were developed via azeotropic distillation. The effect of solution pH on the precursor morphology and microstructure and the mechanical properties of the corresponding alloys was investigated. When the solution pH increased from 2 to 8, a larger number of bonding Zr(Y)O2 particles could be observed in the alloys. The W-Zr(Y)O2 alloy fabricated with the pH 2 precursor powder exhibited a better microstructure and mechanical properties (relative density, micro-hardness, yield, and ultimate strength) than the alloys prepared with pH 5 and 8 precursor powders. The ultimate compressive strength and failure strain of the pH 2 alloy were 1009 MPa and 0.22, respectively. In addition, this alloy contained finer particles than the pH 5 and 8 alloys. The grain sizes of W-Zr(Y)O2 alloys fabricated with pH 2, 5, and 8 precursor powders were in the range of 2–6 μm, which implies that they were much smaller than the particles in pure tungsten. Due to a complicated abrasion mechanism, the wear resistance of the W-Zr(Y)O2 alloys initially increased and then decreased with an increase in the Zr(Y)O2 content. Finally, we could confirm that the alloy fabricated with the pH 2 precursor powder (with 3.0 wt.% Zr(Y)O2) exhibited the most optimal chemical composition, microstructure, and compressive properties. In addition, the wear resistance of the W-Zr(Y)O2 alloy fabricated with the pH 2 precursor powder was characterised. Finally, we expect that the results outlined in this study will act as basic guidelines for the fabrication of ODS-W alloys by liquid-liquid doping.