Microstructure and properties of WMoCu refractory alloys with skeleton structure fabricated by laser powder bed fusion

Abstract

WMoCu refractory alloys were fabricated via LPBF using spray granulation-plasma spheroidized WMo alloy powders and Cu powders. The as-fabricated WMoCu refractory alloys could attain a relative density exceeding 99 %, featuring a continuous WMo solid solution skeleton that encapsulates Cu phase within interconnected interstitial gaps. Microstructural characterization demonstrates a bimodal grain structure of refined WMo grains coexisting with relative coarse Cu grains. Residual stresses and localized strain accumulation originate from the thermos-physical mismatch between WMo and Cu phases during LPBF solidification. Residual compressive stress exists in the WMo phase, while Cu phase alleviates tensile stresses through dislocation slip and grain boundary migration, which induces strain-driven reorganization of dislocations into low-angle grain boundaries (LAGBs). Compared to conventional WMoCu alloys fabricated by powder metallurgy, the WMoCu alloys show enhanced compressive strength but compromised thermal conductivity and electrical conductivity. The WMo solid solution effect simultaneously induces solid solution strengthening and promotes grain refinement during LPBF processing, thereby significantly improving the strength. Conversely, the combined solid solution and grain refinement substantially enhance electron and phonon scattering mechanisms, resulting in a notable reduction in electrical and thermal conductivity.