Effects of Ti Sheet Insert on Microstructure and Properties of Graded Composites of TiB 2 -based Ceramic and Ti-6Al-4V Alloy

Abstract By inserting Ti sheet between ceramic powder and Ti alloy steel, (TiC-TiB 2 )/Ti-6Al-4V graded composites were rapidly prepared by SHS centrifugal-casting process with different Ti sheet thickness from 0.5 to 1.5 mm. XRD, FESEM and EDS results show that there is no significant change in phase composition of the ceramic matrix after inserting Ti sheet, but the inserting promotes the microstructure refinement of the reaction products with the thickness increasing. Meanwhile, the introduction of Ti sheet not only enhances the thickness of the gradient interface, but also decreases the thermal infected zone of interface. Moreover, fusion bonding and atomic interdiffusion between liquid TiC-TiB 2 and excessive Ti liquid in thermal vacuum circumstances are considered to initiate peritectic reaction of TiB 2 (s) + Ti(l) → 2TiB(s), direct growth of TiB solids from liquid Ti and eutectic reaction of TiB solids and liquid Ti at the final stage of joint solidification, so that consumption of TiB 2 solids and increase of TiB crystal relieve the interface residual stress, and the joint of the ceramic to Ti alloy is achieved in multilevel and multi-scale microstructure. The joint represents a transitional change in Vickers hardness and gets a high shear strength of (316±25) MPa between the ceramic and Ti alloy.