Effect of rare earth elements addition on the tribological behavior of AZ91D magnesium alloy at elevated temperatures

The effect of 1, 2, and 3 wt% of lanthanum-base rare earth (RE) element additions on the wear behavior of AZ91 alloy was investigated under a normal load of 20 N at the wear temperatures of 25-250 degrees C. The wear tests were carried out using a pin-on-disk tribometer at a sliding speed of 0.4 ms(-1) for a sliding distance of 1000 m. The results showed that there was no change in the wear rate of the alloys at the wear temperature of 25 degrees C. By increasing the wear temperature to 100 degrees C, the wear rates of AZ91 and the RE-containing alloys decreased by about 58% and 40%, respectively. At higher wear temperatures, the wear of AZ91 alloy increased as a result of softening of beta-Mg17Al12 intermetallics resulting in severe plastic deformation and adhesion on the wear surface. However, the wear of the RE containing alloys decreased as the wear temperature increased to 200 degrees C due to the formation of stable oxide layers on the worn surfaces. The alloy containing 3 wt% RE exhibited the highest wear resistance at the wear temperatures of 150 and 200 degrees C. Further increase in the wear temperature to 250 degrees C led to severe plastic deformation and high adhesion of the alloys. (C) 2013 Elsevier B.V. All rights reserved.