ELEVATED-TEMPERATURE BEHAVIOR OF RAPIDLY SOLIDIFIED MAGNESIUM ALLOYS CONTAINING RARE-EARTHS

The microstructure and mechanical properties of bars of six magnesium alloys (AZ91, AZ151, ACa54, ZE41, WE43 and WE54) extruded from melt sp un ribbons, were investigated. At room temperature, the 0.2% proof str ess for all the alloys (300-500 MPa) is much higher than that of comme rcial cast magnesium alloys. As far as the effect of temperature is co ncerned, the alloys can be separated into two classes: whereas in the case of AZ91, AZ151, ZE41 and ACa54, the yield stress of the bars decr eases rapidly as soon as the temperature increases, it remains very hi gh up to about 150 degrees C in the case of WE43 and WE54, before rapi dly decreasing. Furthermore, the creep resistance of WE alloys is far better than that of AZ alloys. The high yield stress at low temperatur e is ascribed to a strong Hall-Fetch effect (mean grain size similar t o 0.5 mu m). The medium and high temperature behaviours are discussed, with emphasis on the particular case of WE alloys.