Abstract: Toughness of SPF/DB interfaces according to the process parameters, and further, a corresponding interfacial fracture toughness analysis and prediction software system for TC4/TA2 are developed. For the calculating method, first, based on the theoretical analyses and experimental results, the growing model of the diffusion bonded interfaces is established, then the formula for calculating the thickness of interface layer is obtained and the calculation for material transition parameter m is established. Secondly, the modified general criterion for fracture toughness under mixed-mode loading is proposed for fitting the functional model of the fracture toughness curves of the interfaces in the diffusion bonded component. The results that are computed agree very well with experimental data. The analytical results show that within the limits permitted of process parameters, the fracture toughness increases with increase in forming temperature, forming pressure and in time applied pressure. Among them, the influence of forming pressure is maximum, the influence of time and temperature are in proper order. In order to increasing the interfacial fracture toughness of the components diffusion-bonded, the fracture mode mixture of the fracture tip in the interfaces must be increased with the interfacial layer design. The process parameters above mentioned are just concerned with the fracture mode mixture of the fracture tip closely.

Key words: Interface layer, Titanium alloy, Diffusion bonding, Fracture toughness, Superplastic forming