Effect of heat treatment on microstructure and mechanical properties of TiAl/Ti₂AlNb joint by spark plasma diffusion bonding

Abstract

TiAl/Ti2AlNb dissimilar alloys were successfully bonded together by spark plasma diffusion bonding. The joints were subjected to post-weld heat treatment at different temperatures. The microstructure of the welded joint was analyzed and the tensile strength and microhardness of the joint were tested. The results indicate that after heat treatment, the microstructure of Ti2AlNb base metal, TiAl base metal and interface has no obvious change. In the Ti2AlNb heat affected zone(HAZ), most B2 phase gradually turns into O phase, due to the precipitation of acicular O phase, the microhardness increases significantly compared to as welded condition. With the increase of heat treatment temperature, the microhardness of the Ti2AlNb HAZ gradually decreases, meanwhile, the tensile strength of the joint at room temperature shows an evident increase compared to as welded. The maximum tensile strength of the joint reaches 376 MPa at heat treatment temperature of 900℃. After heat treatment, the fracture mode of the joint is brittle fracture.

Keywords

• spark plasma diffusion bonding
• tial
• ti₂alnb
• tensile strength
• microhardness