Study of a Bimetallic Interfacial Bonding Process Based on Ultrasonic Quantitative Evaluation

The interfacial bonding process and mechanical properties of AISI (American Iron and Steel Institute) stainless steel/Q235A carbon steel were investigated by deformation bonding, heat preservation, and tensile tests. The results reveal that the deformation temperature has a beneficial effect on the bonding rate, and that the critical temperature for the large-area bonding of stainless steel and carbon steel is approximately 700 °C. However, owing to the short contact time, only a shallow diffusion of approximately 2–3 µm can be achieved. A slight decrease in the interfacial bonding rate after heat preservation is correlated to the difference between the thermal expansion coefficients of the two materials, but the thickness of the diffusion layer shows a significant increase. It was found that the strength of the composites is mostly related to the bonding rate and the strength of the relatively soft material, which can be determined using an explicit equation. Moreover, with the increase in the interfacial bonding rate, the crack source changes from the junction of the unbonded and bonded areas of the interface to the interior of the carbon steel. The failure mode evolves from cleavage brittle fracture to ductile–brittle mixed-mode fracture, and then to ductile fracture.