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.
Machining magnesium—a study of ignition factors
Sparks and flares are potentional ignition sources in dry magnesium machining. An extensive series of tests was conducted to determine limits within which magnesium machining fires can be avoided or minimized through adjustment of environment and machining conditions.
Creep and Corrosion Properties of the Extruded Magnesium Alloy Containing Rare Earth
Effects of microstructures on the creep and corrosion properties were investigated in the Mg-8A1 alloys with addition of the rare earth elements (La-rich Mischmetal, RE). The addition of RE to Mg-8A1 alloy may form a stable intermetallic phase, Al 11 RE 3 at elevated temperature, and suppress the βhase (Mg 17 Alj 2 ) with poor stability at high temperature. The corrosion rate of the alloy slightly decreases with increasing the added RE contents. The constant-load creep behavior was examined at 423, 448 and 473 K under stresses between 40 and 100MPa. The RE-containing alloy showed a prolonged period of stead-state creep compared to the Mg-8Al base alloy and slightly reduced minimum creep rates. A stress exponent of 2 estimated suggests that the creep behavior can be controlled by the grain boundary sliding. The apparent activation energy for creep of Mg-8Al and Mg-8Al-2RE alloys are 114 and 104 kJ mol -1 , respectively.