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techniques. It is now used in the joining of brittle materials and dissimilar materials [6][7][8]. Fe 3 Al and Q235 steel can be bonded by using the vacuum diffusion bonding technology. However, the stress in the Fe 3 Al/Q235 diffusion bonded joint still is a key that limits the interfacial strength. It is nearly impossible to exactly measure the stress distribution of a diffusion bonded joint. Up to now, researchers pay more attention to the calculation of the stress using various engineering analysis software, programming or finite element analysis [9][10][11]. But few reports are given to the study on stress in the Fe 3 Al joint.In this paper, Fe 3 Al intermetallics and Q235 steel are bonded using vacuum diffusion bonding technology. The interfacial shear strength was measured and the stress of Fe 3 Al/Q235 diffusion bonded joint was analyzed using finite element analysis (FEA). During the stress analysis, the various major thermal-physical properties of the materials under the condition of diffusion bonding were considered. Experiment materials and method Joint preparation and materials definitionThe materials used in the test are Fe 3 Al intermetallic and Q235 carbon steel. Fe 3 Al is melted by using a vacuum induction furnace and then fabricated into a plate using a heat press. Their chemical compositions and thermo-physical performances are shown in Table 1. The sample sizes of Fe 3 Al and Q235 steel are 100 mmx20 mmx20 mm and 100 mmx 20 mmx8 mm, respectively.The oxidation films on the surface of Fe 3 Al and Q235 steel are eliminated by mechanical and chemical methods before diffusion bonding. After that, the plates of Fe 3 Al and Q235 steel are overlapped and then are welded using a Workhorse II vacuum diffusion bonding equipment. The heating power is 45 kW. A series of technology parameters used in the test are: heating temperature T = 1000-1080°C, holding time Abstract Fe 3 Al intermetallics and Q235 steel are bonded using vacuum diffusion bonding technology. The interfacial shear strength was measured and the stress of Fe 3 Al/Q235 diffusion bonded joint was analyzed using finite element analysis (FEA). The results indicate that interfacial shear strength increases from 39.9 to 112.3 MPa with the enhancement of heating temperature from 1000 to 1060°C. Also, shear fracture has more characteristics of cleavage fracture. The farther from the central axis of the interface, the larger the stress is, and the maximum stress appears on the surface of the joint. The maximum stress increases with the heating enhancement and increase of material thickness. When the thickness reaches a critical value (6 mm) and then increases, the stress increases slightly and even to a stable value.