In this study, intermetallic TiAl and steel 40Cr are diffusion bonded successfully by using a composite barrien layer Ti/V/Cu. The relationship of the bond parameters and tensile strength of the joints was discussed, and the optimum bond parameters were obtained. The reaction products and the interface structures of the joints were investigated by SEM, EPMA and XRD. In this case, a diphase Ti3Al+TiAl layer and a Ti solid solution which enhance the strength of the joint are obtained at the TiAl/Ti interface. Formation mechanism at the interface of TiAl/Ti was propounded. The whole reaction process can be divided into three stages. In the first stage, Ti (ss.Al) layer is formed at the interface TiAl/Ti40Cr. In the second stage, TiAl+ Ti3Al layer are formed adjacent to TiAl, in the mean, the continuous diffusion of Al atoms from TiAl to Ti gives occasion to the formation of Ti3Al. In the last stage, the thickness of each reaction layer increases with bonding time according to a parabolic law. The interface of TiAl/Ti/V/Cu/40Cr was free from intermetallic compounds and other brittle phases, and the strength of the joint was as high as 420MPa, very close to that of the TiAl base. This method gives a reliable bonding of intermetallic TiAl and steel 40Cr.

The development of thermal stress during the diffusion bonding of Al2O3 ceramic to Al is analyzed by the finite-element analysis using MARC/MENTAL code. Prior to diffusion bonding, a Cu layer of 0.2mm in thickness is sintered on the ceramic. The results show that shear stress concentration occurs in the ceramic near the corner of Al2O3/Cu interface, and tensile stress concentration occurs near the corners of Al2O3 outer surface during cooling from bonding temperature to room temperature. After tensile stress concentration on the Al2O3 undersurface rises to a certain value, ceramic deforms gradually, resulting in stress beginning to relax. The stress relaxation originates in the stress concentration region of Al2O3 outer surface.

The microstructures of the TiC cermet/steel joint brazed with Ag-31Cu-23Zn brazing alloy (1123K, 20min) and Ag-54Cu-33Zn brazing alloy (1123K, 20/25min) were investigated. When the amounts of Cu and Zn increase in the brazing alloy, there are not many Cu-base solid solution stripes and blocks but few Cu-base solid solution blocks occurred in the middle of the brazing alloy.

Through eliminating voids not affecting the primary bonding process, and incorporating interlayer and flexible base material, the interface geometry character and brief mathematics process was put forth. Through analyzing contact process of diffusion bonding, contact area model was settled. It can interpret the phenomenon of different interface areas taking on different strengths. In the course of physical contact, shear stresses serve an important function for the plastic deformation and the cohesion of interface voids.