RF plasma spheroidization of IMI834–TiB_w composite powders: Microstructural inheritance and deformation mechanisms of SPS-consolidated composites

TiB_w-reinforced titanium matrix composites offer high specific strength and thermal stability, making them attractive for aerospace applications, while pre-alloyed spherical powders are promising feedstocks for near-net-shape processing. In this study, HDH-crushed irregular IMI834–TiB_w composite powder was spheroidized by radio-frequency (RF) plasma and subsequently consolidated by spark plasma sintering (SPS), with IMI834 alloy processed under the same conditions as a reference. Plasma spheroidization and subsequent micro–nano separation produced highly spherical powders with improved flowability and apparent density, while nanoindentation hardness increased from 2.8 ± 0.2 to 8.7 ± 0.5 GPa. The nanoscale TiB_w formed during rapid solidification favored α′-Ti nucleation at TiB_w/matrix interfaces, thereby facilitating the β→α′ transformation and grain refinement. Silicides evolved from (Ti,Zr)₅Si₃ toward (Ti,Zr)₆Si₃, likely because of Si redistribution and partial loss. After SPS, the composite exhibited a fine equiaxed matrix with dispersed nano-TiB_w, whereas the alloy developed coarse α′/β colonies with a higher β fraction. In the composite, TiB_w participated in load transfer and impeded dislocation motion, contributing to a higher early-stage work-hardening rate. Cracks propagated predominantly along the fine grain-boundary network, forming a more tortuous path than in the alloy. Limited plastic accommodation associated with the lower β fraction, together with local TiB_w fracture promoted by strain concentration, may have contributed to the lower fracture strain. These results show that microstructural features formed during RF plasma spheroidization are partly inherited after SPS and influence deformation and fracture mechanisms.