Innovative insight for microstructural regulation of intermetallic compounds in Ti/Al dissimilar alloy laser welding: Micro-surface texturing via pulsed laser pretreatment

The welding of dissimilar Ti/Al hybrid structures is recognized as a critical technology for the high-performance/ lightweight fabrication of aerospace and high-speed transportation components. Laser brazing welding, a recognized method for Ti/Al joining, is challenged by the formation of brittle intermetallic compounds (IMCs), which significantly compromises joint mechanical. Herein, pulsed laser pretreatment (PLP) is employed to butt surface, effectuating a 40 % enhancement in tensile strength of Ti/Al dissimilar joint under laser brazing welding. The influence of PLP on evolution of IMCs is comprehensively understood by numerical simulation. PLP induces a turbulent flow at Ti/Al interface and enhances thermal diffusion on Ti side, resulting in alternating distribution and diverse crystallographic orientations of IMCs with an average thickness reduced to 2 mu m. Thereupon, the fundamental relationship between IMCs structure and mechanical performance is illuminated by exploring joint fracture failure behavior. PLP promotes the stochastic distribution of Ti3Al, curbing the cracking of brittle phase and its interfaces within IMCs layer, diverting crack propagation paths and markedly reducing extension rates, thereby effectively enhancing tensile strength. This article heralds a considerable advance in understanding the formation and fracture of IMCs for Ti/Al system. It further furnishes novel and unique insights into the improvement strategies for mechanical properties of Ti/Al dissimilar joint, based on surface texture "Riveting" and IMCs structure "Pinning".