In this study, intermetallic TiAl and steel 40Cr are diffusion bonded successfully by using a composite barrien layer Ti/V/Cu. 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. 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 maximum value of thermal stress and stress concentration zones of iron/TiC cermet joint during cooling were studied in this paper. The results show: the shear stress on iron/TiC cermet joint concentrates on the interface tip and the maximum value of shear stress appears on the left tip of iron/TiZrNiCu interface. Positive tensile stress on TiC cermet undersurface concentrates on both sides of TiC cermet and its value decreases during cooling. Negative tensile stress on TiC cermet undersurface concentrates on the center of TiC cermet and its value increases during cooling. Brazing temperature has little effect on the development and maximum value of thermal stress.

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.