Effect of Al–5Ti–0.3C–0.2B Master Alloy on the Structure and Properties of Ti6Al4V by Laser Solid Forming

Titanium matrix composites (TMCs) with the addition of in situ ceramic reinforcing particulates have attracted extensive interest. Herein, additive-manufactured Ti6Al4V/Al–5Ti–0.3C–0.2B alloys are fabricated from mixed powders by laser solid forming. The contents of Al–5Ti–0.3C–0.2B with 1.5, 2.5, and 5.0 wt% are considered. The results indicate the apparent microstructure transition from columnar grain to equiaxed grain with increasing content of Al–5Ti–0.3C–0.2B. The in situ reaction between the Ti6Al4V and Al–5Ti–0.3C–0.2B produces TiB, TiC, and Ti₃AlC reinforcements. The increase of Al–5Ti–0.3C–0.2B content will refine grains and reduce α′ martensite phase, which is associated with the formation of TiB at the grain boundaries. As the content of Al–5Ti–0.3C–0.2B increases, the ultimate tensile strength of Ti6Al4V–x wt% (Al–5Ti–0.3C–0.2B) alloy increases from 993.8 MPa to 1233.6 MPa. The strength increases because of an increase of the solid phases TiB and Ti₃AlC, which is ascribed to the presence of precipitation and grain refinement strengthening mechanisms. Meanwhile, the elongation of the alloy increases from 1.1% to 4.9% because the Ti₃AlC phase is conducive to reducing thermal transfer and interfacial stress. These findings provide insights into the selection of reinforcement materials for optimizing mechanical properties of TMCs alloys.