Abstract: Based on current theories of diffusion and creep cavity Closure at hign temperatures, a theoretical analysis of diffusion bonding under superplastic condition for Ti-6 A1--1 V titanium alloy is carried oul. The diffusion bonding is mainly described us a two -stage process:1 The shrinkage process of cavities with shape change from elliptical to cylindrical:2 In the second stage, the radii of the cylindrical cavities are reduced and eliminated.In this paper, the mathematical model is established in order to predict the bonding quality which are affected by technological parameters, such as temperature, pressure, bonding time etc. Meanwhile the reasonable technological parameters are chosen from theoretical analysis. The theoretical analysis is in good agreement with experimental results.

Key words: diffusion bonding, superplastie condition, Ti-6 Al-4 V alloy