Microstructure and Fracture Behavior of the Joint of Solidified TiB<sub>2</sub> Ceramic with Ti-6Al-4V Achieved by Reaction Fusion Bonding in Ultrahigh-Gravity Field

Abstract

Based on taking combustion synthesis in ultrahigh-gravity field to prepare solidified TiC-TiB2 ceramic, laminated composite of TiC-TiB2 to Ti-6Al-4V was successfully obtained by fusion bonding, and within the joint there achieved multi-scale (micron-submicron-micro-nano) and multi-level (TiC1-x-TiB-TiB2 + TiB2-Ti-TiC1-x-TiB + TiB2-TiC1-x-TiB-Ti + TiB-TiC1-x-Ti + TiC1-x-Ti + Ti) composite structures characterized by size and distribution of TiB2 and TiB phases. As micro-nano TiB2, TiB platelets and needle-like nano TiB grains at the joint area initiated residual stress toughening and pinning at crack tip, while Ti phases initiated ductile phase toughening and subsequent bridging in crack-tip wake, a typical delayed fracture under external stress was manifested obviously in the joint of TiC-TiB2 to Ti-6Al-4V. As a result, the shear fracture of the joint of ceramic toTi-6Al-4V alloy usually occurred in solidified area of Ti alloy rather than the joint, and the shear strength between the ceramic and Ti alloy was maintained at 375 ± 55 MPa.