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

Abstract

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 μm. 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”.