Mechanical properties and microstructure of Ti–6.5Al–2Zr–1Mo–1V/TiB composites produced by vacuum arc or selective laser melting

Abstract

Ti–6.5Al–2Zr–1Mo–1V/TiB metal-matrix composites were produced by vacuum arc or selective laser melting (SLM) methods using 0.7 and 2 wt.% TiB₂ in the charge mixture. The initial microstructure of the as-cast and SLM composites consisted of TiB fibers randomly distributed within the two-phase α/β matrix. The average apparent length and cross-sectional size of the TiB fibers in the as-cast composite with 0.7 wt.% TiB₂ and as-cast composite with 2 wt.% TiB₂ were ~10 and ~11 μm and ~ 1.0 and ~ 1.2 μm, respectively. The average apparent length and cross-sectional size of the TiB fibers in the SLM composite with 0.7 wt.% TiB₂ and the SLM composite with 2 wt.% TiB₂ were ~3.5 and ~4.0 μm and ~0.2 and ~0.25 μm, respectively. The addition of the TiB fibers resulted in 20–27% increase in the strength without visible decrease in the ductility. An unreinforced alloy produced by the SLM showed 60% increase in strength compared to that obtained by the vacuum arc melting. The addition of the TiB fibers resulted in ~30% increase in the strength (for both composites) with a decrease in the ductility to 8 and 3% for the SLM composite with 0.7 wt.% TiB₂ and the SLM composite with 2 wt.% TiB₂, respectively.