Chip morphology and combustion phenomenon of magnesium alloys at high-speed milling

Due to the lower ignition point and higher chemical activity of the magnesium alloy, the chips would combust easily at high-milling temperature, which would trigger a security issue. In this paper, the magnesium alloy chip morphology and combustion state variations of the chip were analyzed during the high-speed milling. Based on which the coupling relation among the chip morphology, the combustion state and the milling parameters were established. The high-speed milling experiments of the AM50A and AZ91D magnesium alloys were executed; whereas, the changes of the Al-Mn and β-Mg₁₇Al₁₂ phases in the magnesium alloys prior to and following milling were compared and analyzed. The main alloy phases that caused the chip combustion were pointed out. The chip combustion cause was explained from the magnesium alloy compositions; whereas, the reasons for the AZ91D magnesium alloy ease to catch fire and higher combustion strength compared to the AM50A magnesium alloy under the same conditions were obtained.