Optimising multiple qualities of Nd:YAG laser welding onto magnesium alloy via grey relational analysis

This work evaluates multiple quality optimisation of Nd:YAG laser welding onto magnesium alloy via grey relational analysis. The effectiveness of the grey relational grade lies in quantifying and judging the performance obtained using various combinations of laser welding parameters. The parameters are shielding gas, laser energy, travelling speed of workpiece, point at which the laser is focused, pulse frequency, and pulse shape in this work. Moreover, 18 combinations of these six essential welding parameters were set following Taguchi's method to evaluate the integrated performance. The welding parameters that govern the laser beam in thin plate butt welding were evaluated by measuring the ultimate tension stress, and both the depth and the width along the welding path. This integrated performance was then quantified and judged via grey relational analysis to obtain an optimised set-up for laser welding. The verifying test was proved to optimise the ultimate tension stress, depth and width along the welding path from 67·0 MPa, 0·50 mm and 0·77 mm to 142·3 MPa, 0·79 mm and 0·79 mm, respectively.