DIFFUSION BONDING OF 2 PHASE GAMMA-TIAL ALLOYS WITH DUPLEX MICROSTRUCTURE

Solid state diffusion bonding of TiAl was carried out with different b onding parameters within the superplastic temperature range. The effec t of post-bond heat treatment (PBHT) on the mechanical properties of t he bonds was also studied. Defect free sound bonds were achieved withi n the temperature range 925-1150 degrees C and the pressure range 20-4 0 MPa. Transverse microtensile specimens extracted from the bonds were tested to evaluate room temperature tensile properties of the bonds a nd to correlate them with bonding parameters. The bond strength increa sed with an increase in bonding temperature and pressure. All the spec imens of the bond made at 925 degrees C and 40 MPa, and most of the sp ecimens of bonds made at 1000 degrees C and 30 MPa and at 1100 degrees C and 20 MPa, failed in the bond area; all the specimens of bonds mad e at 1100 degrees C and 30 MPa and at 1150 degrees C and 20 MPa failed in the bond area; all the specimens of bonds made at 1100 degrees C a nd 30 MPa and at 1150 degrees C and 20 MPa failed in the base metal. P ost-bond heat treatment at 1350 degrees C for 1 h led to the transform ation of the recrystallised gamma grains were also formed away from th e bond area in the bonds made at 1100 degrees C and 30 MPa and at 1150 degrees C and 20 MPa. After PBHT, these bonds exhibited slightly lowe r tensile strength values owing to the change in the base metal micros tructure away from the bond area. (C) 1997 The Institute of Materials.