Develop a new strain rate sensitive solid-state pressure bonding model

Abstract

Solid-state bonding is widely involved in metal forming and joining applications. The quality of the bonded interface is the key to the final integrity of the joint or formed structure; thus, its controllability and predictivity have been the focus over decades. The interface bond quality is jointly determined by the interface oxide behaviour and microstructure evolution. In this study, a new four-stage model, considering the cohesion of different contacting pairs (oxide-oxide, oxide-metal and metal–metal) and the reduced adverse effect of remaining oxides, is proposed to describe the bonding process under hot deforming conditions. This proposed model was validated through a range of hot compression bonding tests, using Gleeble under different strains (10%, 30% and 50%), strain rates (0.001 s−1, 0.01 s−1 and 0.1 s−1) at 1150 °C with references. Scanning electron microscope (SEM) and Electron Backscatter Diffraction (EBSD) were used to characterize the oxide behaviour and microstructure evolution. Tensile tests at room temperature were conducted on bonded samples and references to reveal the interface bond ratio. 100% bonding strength, equivalent to the base metal's strength and ductility, was achieved at the large strain of 50% for all three strain rates.