Microstructural evolution and growth kinetics of interfacial compounds in TiAl/Ti3SiC2 diffusion bonding joints

TiAl intermetallic was direct diffusion bonded to Ti 3 SiC 2 at 900 °C, 950 °C, and 1000 °C with a holding time ranging from 0.25 h to 64 h. The interfacial microstructural evolution , the growth kinetics and the mechanical properties of the bonded TiAl/Ti 3 SiC 2 joints were systematically investigated. The build-up of interfacial compounds in the TiAl/Ti 3 SiC 2 joints changed from γ+α 2 /γ/Ti 5 Si 3 /Ti 3 SiC 2 to γ+α 2 /γ/TiAl 2 /Ti 5 Si 3 /Ti 3 SiC 2 , to γ+α 2 /γ/TiAl 2 /Ti 5 Si 4 /Ti 5 Si 3 /Ti 3 SiC 2 , and to γ+α 2 /γ/TiAl 2 /TiAl 3 +Ti 5 Si 3 /Ti 5 Si 4 /Ti 5 Si 3 /Ti 3 SiC 2 as the holding time or bonding temperature increased. The formation sequence of interfacial phase at the joint was: Ti 5 Si 3 →Ti 5 Si 4 →TiAl 2 →TiAl 3 . The de-intercalation Si atoms from the Ti 3 SiC 2 diffusing into the TiAl base alloy and reacting with the Ti was responsible for the formation of the interfacial reaction layers. The thicknesses of the interfacial reaction layers grew following the parabolic kinetic law, indicated their growth was controlled by the bulk diffusion . The bonding activation energy was 213 kJ/mol. The joint, bonded at 900 °C for 9 h, had the highest shear strength (about 53 MPa) with a γ+α 2 /γ/TiAl 2 /Ti 5 Si 4 /Ti 5 Si 3 /Ti 3 SiC 2 interfacial microstructure and with a total thickness of 6 μm.