Microstructure evolution of SiC/Ti6Al4V titanium matrix composites during heat treatment

The Ti6Al4V alloy and Ti6Al4V-SiC composites were prepared by the selective laser melting method. The influence of different heat treatment systems on the microstructure of the two materials was comparatively studied, revealing the strengthening mechanism of the Ti6Al4V-SiC composite material. The main conclusions are as follows: With the increase of solution temperature, the metastable phase α' martensite of the Ti6Al4V alloy formed by SLM gradually decomposes. After the precipitation of the β phase (α'→β) and the transformation of α' martensite to the α phase (α'→α), an α+β biphasic structure is eventually formed. However, due to high temperature, the α phase coarsened and the tissue became uneven. The in-situ formed TiC particles in the Ti6Al4V-SiC composite material transform α' martensite into granular α phase, forming randomly distributed TiC particles and a more uniform α+β biphase structure. Meanwhile, the nano-Ti5Si3 particles distributed at the α/β interface limit the growth of the α phase, resulting in a finer structure.