Microstructure development and wear behavior of Al-15% Mg2Si-xGd composites before and after hot extrusion

The brittleness of Mg2Si particles in the Al-15%Mg2Si composites needs modification in order to enhance the structure and improve mechanical properties. The influence of Gd additions on the microstructure of primary Mg2Si phases and wear behaviour of Al–Mg2Si before and after the hot extrusion process was investigated. The results showed that the addition of 1.0 wt.% Gd modified the primary Mg2Si morphology but exceeding this level of Gd induced a loss of modification as the primary phase morphology coarsened again. Microstructural analysis results revealed that with 1.0 wt.% Gd addition to Al-15%Mg2Si composite the average particle size and aspect ratio decreased by about 147% and 38.7%, respectively. The results of wear test also showed that composites treated with Gd have higher wear resistance compared with those of without Gd. The highest wear resistance was observed as 0.09517 mm3/km and 0.04953 mm3/km in the composite containing 1.0 wt% Gd for before and after the hot extrusion process, respectively, which is likely the result of effect of hot extrusion in good dispersion of fine Mg2Si particles in the Al matrix