Experimental evaluation of cut quality and temperature field in fiber laser cutting of AZ31B magnesium alloy using response surface methodology

Fiber laser cutting of AZ31B magnesium alloy was studied to assess the effect of laser cutting process parameters on the resultant cutting temperature near the cut kerf and the resultant cut quality. To systematically analyze the effect of parameters on the temperature variation and cutting edge surface roughness during the cutting process of the AZ31B magnesium alloy, the Response Surface Methodology (RSM) was utilized to fit a quadratic polynomial model through the experiments. The influence of three main factors including speed of cutting, power of laser and nozzle distance on the major responses of temperature near the cut kerf, average surface roughness of the cutting edge and the cut kerf quality was then evaluated. Changes in the cutting speed had no serious impact on the quality of the cut kerf. Laser power levels from 800 to 1000 W were suitable for laser cutting of magnesium alloy sheets. The results showed that variations in the nozzle distance and laser emitted power had a remarkable effect on the temperature variation around the cut kerf width. Changing the nozzle distance and thereby creating different laser beam diameter had a more significant influence on the temperature variation rate (about 15 %), in comparison to the laser power. The nozzle distance had a huge effect on the cutting edge surface roughness due to the significant variation of laser beam energy density and beam diameter and hence, the cut kerf dimensional changes. The optimal cutting condition was obtained at the minimum roughness according to the investigated parameters levels, which included the cutting speed of 6 m/min, the power level of 1000 W and the nozzle distance of 0.8 mm. The SEM images from the top surface of the cut kerf implied the existence of oxidation in the magnesium alloy kerf edges.