Tribological behavior of AZ91D magnesium alloy at elevated temperatures

The wear behavior of AZ91 magnesium alloy was investigated under applied loads of 5, 20 and 40 N at the wear testing temperatures of 25 °C to 300 °C. The wear tests were carried out using a pin-on-disk tribometer at a sliding speed of 0.4 ms−1 for a total sliding distance of 1000 m. The examination of worn surfaces showed that the abrasive wear was the main mechanism at 25 °C under the loads tested. The results showed that under a normal load of 40 N, rising the wear temperature increased the wear rate. However, under a normal load of 20 N the wear of the alloy decreased by about 58% as the wear temperature increased to 100 °C. Further increase in the wear temperature to 250 °C resulted in an increase in the wear of the alloy due to the softening and dissolution of β−Mg17Al12 phase. Under a normal load of 5 N, the wear rate decreased as the wear temperature increased to 250 °C. Under a specific normal load, there was a critical surface temperature at which a transition from a mild to a severe wear mechanism might occur. These temperatures were about 140, 180, and 400 °C at the normal loads of 40, 20, and 5 N, respectively.

► Tribological behavior of AZ91 was studied in a wide range of temperatures and loads.
► Critical surface temperatures for a mild to a severe wear transition were found.
► Dissolution of β−Mg17Al12 could affect the wear of AZ91 alloy at high temperatures.