Microstructure evolution during preparation of in-situ TiB reinforced titanium matrix composites

By means of DTA, SHS quenching, XRD and SEM, the microstructure evolution during fabricating of TiB reinforced in-situ titanium matrix composite was studied. DTA result shows that there are two exothermic and one endothermic reaction during heating of Ti-B-Al system. The exothermic reactions correspond to the solid-solid diffusion reaction between Ti and Al, and the reaction of TiB formation respectively, and the endothermic reaction corresponds to melting of Al. The sample of SHS quenching presents four regions: unreacted region, heat-affected region, reacting region and product region. The microstructures of these regions reflect the process of microstructure evolution during preparation of in-situ TiB reinforced TMC. Ti, B, Al powders are in simple mechanical contact in the unreacted region; the sharp angles of original metal particles have become round and B diffuses into melted Al in the heat-affected region; TiB whiskers begin to appear and grow in the interior of reacting region. In product region, the TiB whiskers are uniform and fine. The result of XRD indicates that the reinforcements formed in product region are TiB whiskers. And the TiB is a hexagonal prism with a pyramidal head.