In-situ reinforced Ti6Al4V-TiB2 titanium matrix composite fabricated by selective laser melting: Microstructure, mechanical properties and heat treatment

Ti6Al4V-x wt%TiB2 titanium matrix composites (x = 0, 0.01, 1, 3.4, 4.8) were prepared by selective laser melting (SLM), followed by solution-aging treatment. The microstructure and mechanical properties of the SLM-formed samples and the heat-treated ones were systematically investigated. In the SLM-formed samples, in-situ TiB whiskers clustered around the original position of the TiB2 particles, which reacted with the matrix through dynamic dissolution. The phase transformation of α' → α + β and the coarsening of TiB whiskers occurred during solution-aging treatment. The microhardness of the samples was enhanced with the increase of TiB2, while the heat treatment was harmful to microhardness. The fine grain strengthening and the dispersion strengthening caused by TiB whiskers enhanced the quasi-static compressive strength of the samples. The samples were modified successfully by solution-aging, and the compressive strength and strain of the Ti6Al4V-0.01wt.%TiB2 composite reached 1957 MPa and 23.7% respectively. The samples had higher ductility but lower strength under dynamic load, and the heat treatment had little effect on the dynamic properties.