Chip ignition in research on high-speed face milling AM50A magnesium alloy

The ignition of magnesium alloy chips is a problem during high speed dry machining in industry. It should be avoided in the practical production. Many factors including machining environment, material composition, tool geometry, cutting parameters etc. can influence the cutting processes. Among these factors, cutting parameters is one of most important elements to induce the ignition of magnesium alloys. AM50A is a commercial magnesium alloy which is widely used in industry. However, very few reports about the ignition conditions of AM50A magnesium alloy are available. In this paper, we investigated the ignition conditions of AM50A magnesium alloy at different cutting parameters. The relationship between ignition conditions and chip morphologies was further explored. The macro morphologies of the chips were observed by optical microscope and the micro structure were obtained by scanning electron microscope (SEM). It is found that the macro morphologies of chips can be characterized into powdered chip, tubular helical chip, acicular helical chip, and long belt chip, which correspond to the different ignition conditions. The powdered chips and acicular spiral chips are easily ignited. They have thinner lamellar thickness compared to the other two types of chips. These results may be used to analyze cutting process and prevent the chip ignition in dry machining magnesium alloy.