Achieving near equiaxed α-Ti grains and significantly improved plasticity via heat treatment of TiB reinforced titanium matrix composite manufactured by selective laser melting

A facile heat treatment strategy suitable for TiB reinforced titanium matrix composites (TMCs) fabricated by selective laser melting (SLM) is proposed. The effects of boron modification and heat treatment on the microstructure and mechanical properties of the selective laser melted TMC samples were systematically investigated. The ultrafine ∼2 vol% TiB whiskers that formed in situ exhibited a much more homogeneous distribution in the matrix compared to that of conventionally processed composites containing similar volume fractions, further promoting the formation of fine equiaxed α-Ti grains throughout the matrix. An excellent combination of strength and fracture strain of 1428 MPa and 43.6%, respectively, was simultaneously achieved for the heat-treated TMC, in which the plasticity was improved by 126% over that of the as-fabricated composite (19.3%). This finding provides significant guidance for tailoring the microstructure in selective laser melted TMCs to achieve the desired mechanical properties.