Effect of Femtosecond Laser‐Induced Surface Textures on the Microstructure and Mechanical Properties of Mg/Ti Dissimilar Alloys Laser Lap Welds: A Numerical and Experimental Study

The strength of the joints in the Mg/Ti laser welding is difficult to meet the requirement because of the metallurgical incompatibility. In this study, the workpieces of Ti6Al4V and AZ31B are connected via the femtosecond laser welding, and the surface of the Ti alloy is textured with microgrooves, which aim to improve the wettability and spreading behaviors of the molten Mg alloy, and eventually enhance the overall quality of the joints. The influence of microgrooves’ width on the contact angle and spread length of the molten Mg is investigated. The optimal contact angle of 56.4° is achieved at the microgroove width of 100 µm because the leading and trailing edges of the microgroove texture can stimulate the formation of the microriveted structure, facilitating the fluidity of the liquid AZ31B. The joint’s tensile–shear capability is increased to 2449.9 N, which is 2.8 times stronger compared to joints without microgroove textures, when using a microgroove width of 100 µm and a laser power of 52%. The numerical simulation of the laser welding process was implemented to analyze the temperature field and the fluid characteristics within the melt pool. The results showed that the microgroove enhanced the material exchange at the interface and accelerated the interfacial reaction, which stimulates the formation of Ti‐Al and Mg‐Al IMCs at the central interface of the joint and enhances the Mg/Ti metallurgical bonding.This article is protected by copyright. All rights reserved.