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Diffusion bonding of martensitic stainless steel was conducted at different times. Based on the interface characteristic and shear strength, bonding mechanisms were discussed. Results showed that the bonding quality was controlled by void shrinkage and interface grain boundary migration. Large voids with scraggly edges changed to small voids with smooth edges, leading to an increase in interface bonding ratio. Two cases of interface grain boundary migration were revealed: interface grain boundary migration at the triple junction induced by the reduction in grain boundary energy and strain induced interface grain boundary migration resulted from the stored energy. Owing to the void shrinkage and interface grain boundary migration, the shear strength of the joint matched that of the base material.

The interaction process between void and migrating interface grain boundary (IGB) in the bonding interface of 1Cr11Ni2W2MoV steel joints produced by diffusion bonding has been examined, and the corresponding interaction mechanism was analysed. The results showed that there were two cases occurring in void-IGB interaction by comparing the IGB velocity with void velocity: if the IGB velocity exceeded the void velocity, the void would separate from the IGB and be trapped inside the grain; otherwise, the void would attach to and migrate with the IGB. It was also found that the void-IGB interaction was related to the radius of void. The bigger voids easily separated from the migrating IGB, while the smaller voids tended to attach to it. The approximate theoretical values of critical radius of voids for separation/attachment were derived, and they agreed well with the experimental values obtained.

In this paper, data are presented on the microstructure and superplastic deformation mechanics of an aluminum alloy, 2024, containing 10 vol % SiC particles. The material was fabricated by spray atomization and codeposition. The properties were studied after pretreatment by isothermal hot compression and isothermal hot forward extrusion (extrusion ratio 10.0). The experimental results show that the strain-rate sensitivity index (m-value) is 0.48 and the limit elongation (the elongation at fracture) is 345 % during superplastic uniaxial tension. The optimum conditions for superplastic behavior are 753 K of deformation temperature and 1.0 • 10 -3 s -1 of initial strain rate. Superplasticity may result from the fine grain size and the well-distributed SiC particles during superplastic uniaxial tension. Moreover, the simple and convenient pretreatment used in this paper is easily applied to industrial practice. I

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