Changes in Intermetallic Compounds and Mechanical Performance of Steel/Aluminum Welded Joints Containing Nano TiC during Isothermal Aging

Steel/aluminum welded joints are prone to the formation of brittle intermetallic compounds (IMCs), which significantly affect the mechanical performance of the joints. In this study, the isothermal aging process was used to simulate the prolonged heating of chassis welds during automotive operation. A comparative analysis was conducted to investigate the evolution of IMCs at the aluminum interface of two types of steel/aluminum joints, with and without nano TiC, under different aging treatment times. Mechanical performance tests were also conducted on the joints. The results indicate that during the aging treatment the growth of IMCs at the aluminum side interface of both joints is influenced by grain boundary diffusion. The thickness of the IMCs layer increases with time, following a parabolic pattern. The addition of nano TiC reduces the diffusion coefficient of IMCs at the aluminum interface of the joint from 4.652 to 3.233, effectively reducing the growth rate of IMCs, enhancing the mechanical performance of the joint and reducing occurrences of transgranular and intergranular fractures.