Laser Welding-Brazing Process And Microstructure Property Of Al/Ti Joint

Al/Ti bonded structural components, with excellent performances of two alloys, possess comprehensive prospect of aerospace applications. However, the existence of hard and brittle inter-metallic compounds layer in the joint is primary problem for the welding Al/Ti dissimilar alloys, because it causes the property of joint decrease.In this paper, dissimilar metals of Al/Ti are successfully joined by laser welding-brazing process with Al-Si filler which is singled out via comprehensive analysis, which avoid these defects, such as pore, cracks, burning loss of metal elements in laser welding process. It is found that the welding stability is affected greatly by the energy distribution of spot in laser welding-brazing process. The heating of filler metal and baser metals by circular spot with Gaussian distribution of energy is inclined to the burning loss of filler metal and flux, or the bad spread-ability of fused filler metal due to low temperature of base metals.The adoption of elliptic spot obtained by inclined laser beam can enhance the process stability and improve the surface quality of brazed seam. The good joint is got by optimizing the process parameter, such as laser power, welding speed, the speed of filler metal and so on. The average strength of joints is about 298 MPa, over 85% of strength of aluminum. And it is observed that laser power is the ultimate affection of joint strength, the defocusing amount is the weak influence, and the welding speed between the former affection factor.The rectangular spot(4×2mm2) with symmetrical energy distribution make the greatest process stability, the broadest processing parameter and best surface quality of seam, but the power density which ensuring the great spread-ability of fused filler metal can be obtained only by the higher laser power.Furthermore, the interface behavior and bonding mechanism of Al/Ti joints obtained by laser welding-brazing process have been researched The inter-metallic compounds with non-homogeneous distribution in Al/Ti joint is constituted of binary Al-Ti and ternary Al-Ti-Si compounds. The layered inter-metallic compounds with denticular distribution enhance the area of stress, increase the property of Al/Ti joint. The thickness of inter-metallic compounds...