Microstructure and Mechanical Properties of in-situ Synthesized TiB+La₂O₃/TC4Titanium Matrix Composite by Selective Laser Melting

With Ti-6Al-4V titanium alloy powder and LaB₆ powder as raw materials, the in-situ synthesized TiB+La₂O₃/TC4 titanium matrix composite and TC4 titanium alloy were prepared by selective laser melting. The phase compostion, microstructure, hardness and compressive strength of the composite and the titanium alloy were studied and compared. The results show that the microstructures of the composite and the titanium alloy were both composed of columnar β grains and acicular α' martensite distributed in grains. The size of the β grains and α' martensite clusters of the composite were smaller, and the proportion of large angle grain boundary was higher. TiB and La₂O₃ reinforcements were formed by in-situ reaction of LaB₆ and titanium. TiB was elongated and distributed along a certain direction. La₂O₃ was in shape of small spheres, and dispersed on grain boundaries and in grains. The microhardness and room temperature/high temperature compressive strength of the composite were higher than those of the titanium alloy.