Diffusion Bonding Of Gamma-TiAl Alloys To Ti-6Al-4V Alloys

γ-TiAl alloys exhibit low density,excellent high temperature strength retention,better oxidation resistance and good creep properties at high temperatures,etc.,which are one of the most promising materials for high temperature application in the aerospace industry.To ensure their application and to make them more attractive for the potential utilization,the development and adoption of adequate joining techniques have to be conducted simultaneously with the improvement of the properties of these alloys.In the thesis,diffusion bonding between Ti-46.5Al-2.5V-2Cr-1.5Nb and Ti-6Al-4V(in atom percent)alloy under the different conditions were investigated,focusing on the microstructures, compositions and phase constitution in the bond between base alloys.In the meantime,laser rapid solidification method was used to obtain the fine microstructure on the surface of these two alloys,and the effects of the fine microstructure on the diffusion bond process was studied.The results indicated that a sound bond betweenγ-TiAl and Ti alloys could be achieved when joining is carried out at temperatures of 1073K and over, under an applied stress of 100Mpa for 2h.The bond width increased with the increase of bonding temperature; There was a diffusion flux of Al atoms fromγ-TiAl alloys towards Ti alloy and of Ti atoms in the opposite direction,and the process was controlled by interface diffusion; By laser rapid solidification and heat treatment,a very fine microstructure can be obtained,which is benefit to the diffusion bonding; At the conditions of 60MPa/850℃/1h,a sound bond can be obtained in the laser surface treated samples,and the bend strength of the joint reached 82% of that of matrix(TiAl).Finally,the possibility of measurement of the quality of joints by using the ultrasonic non-destructive testing method was discussed.