Study of temperature on microstructure and mechanical properties on Fe/Al joint in laser-assisted friction stir welding

Abstract

Laser-assisted friction stir welding between Q235 steel and 6061-T6 aluminum alloy was studied by numerical and experimental methods in this paper. The mathematical model of heat source, which is from the laser beam, the tool shoulder and the tool pin, is developed respectively. The temperature field is measured by infrared thermography and it is compared with the simulated result under the same condition. The measured result is in good with the calculated result. Besides, the temperature field of wok-piece was calculated at different laser powers and the corresponding tensile strength of the joints were tested and compared. It indicates that laser power is one of the key factors that affect the tensile strength of the joints significantly. Proper laser power can obtain a sound joint. What is more, SEM, hardness test and an optical microscope are used to analyze the fractography of tensile fracture surfaces, hardness profile and the metallographic structure of the joints, respectively. Results show that the welding temperature has a significant effect on the microstructures and the mechanical properties of the joint.