Process parameter optimization of laser welding for dissimilar aluminum alloys 4047 and 6061 using response surface methodology: Microstructure and mechanical properties

Abstract

In this study, continuous fiber laser was used to butt weld 2 mm thick 4047 and 6061 dissimilar aluminum alloys, and the optimization of welding parameters, microstructure and mechanical properties of the joint were studied. The Box-Behnken Design (BBD) response surface test design method was used to optimize three main process parameters: laser power, welding speed and defocusing amount. The optimal process parameter combination was determined as follows: laser power 800 W, welding speed 17.5 mm/s, defocusing amount 0 mm. The accuracy of the prediction model of back-width ratio and effective area under this parameter is as high as 97 % compared with the reality. The welded joint with good weld shape and no defects was obtained. The microstructure of the weld is mainly composed of α-Al matrix and Al-Si eutectic structure, the center of the weld is equiaxed crystal structure, and the near melting zone is columnar dendrite. The main alloy elements of the weld are Al, Si, Mg and Fe, and there is no obvious element segregation. The longitudinal local tensile results show that the tensile strength of the weld metal reaches 260.45 MPa, which is 202.6 % and 83.3 % of the 4047 base metal and 6061 base metal respectively. The elongation is 12.25 %, which is 43.9 % and 98.2 % of 4047 and 6061 base materials, respectively. The above research provides a reference for the connection and application of 4047/6061 dissimilar aluminum alloy.