Abstract
<title>Abstract</title> <p> With the rapid development of the aerospace industry, Al/Ti has received widespread attention as a dissimilar material with excellent properties. Refill friction stir spot welding (RFSSW) has been proven to offer distinct advantages in joining dissimilar materials. However, the interfacial diffusion behavior and mechanical properties of Al/Ti dissimilar material joints remain unclear. This study investigates interfacial metallurgical bonding in Al/Ti joints via RFSSW with varying dwell times, using a combined numerical simulation and experiment. The results indicate that with a prolonged dwell time, both the peak temperature and strain rate increased, resulting in grain coarsening and a thicker diffusion layer in the joint. In agreement with its low Gibbs free energy and interfacial energy, TiAl <sub>3</sub> is identified as the sole intermetallic compound at the interface via transmission electron microscopy. The tensile-shear failure load initially increases and then decreases, reaching a maximum of 6.39 kN at a dwell time of 6 s. This trend is attributed to the presence of coarse grain zone and hard Ti/TiAl <sub>3</sub> particles within the Al plate, which promote crack initiation and propagation. </p>