Study On Microstructures Of Laser Melted Surface And Their Transformation During Treating And Superplastic Forming/Diffusion Bond Of A γ-TiAl Alloy

In this study, advanced Laser surface treatment, Superplastic, Solid-joint technologies were used to the bond of a γ-TiAl alloy to realize the high quality bond of this alloy at low temperature and short time. TEM, SEM, DSC, and X-ray method were used to study the microstructures and their transformation of the Laser melted layer, and superplastic forming bonding process of γ-TiAl was investigated. The results are as follows.After Laser surface treatment, a fine microstructure, containing equiaxed grains, cellular dendrite structure and heat influenced zone can be observed on the surface. This microstructure can transform into the fine microstructure with equiaxed grains when the sample was heated over 900℃. The microhardness of this fine microstructure at 900℃ is far lower than that of matrix. When superplastic forming/diffusion bonding between the surfaces with fine grained structure at the conditions of 900℃ and 60MPa. Three typical processes of SPF/DB occurred. When the bonding time is up to 1hr, sound joints can be obtained. The bending strength is up to 61% of that of the base alloy.