Evaluation of Hardness of Aluminium Metal Matrix Composites at Elevated Temperature

Abstract

Aluminium based composite materials (LM25 alloy) was fabricated by stir casting method at different percentages like 3%, 6%, 9% and 12% weight percentage of MgO. The four samples were prepared by using the above method. Then the four samples are heated at different temperatures such as 200ºC, 300ºC, and 400ºC in the muffle furnace. Then the heated specimens are cooled to room temperature by air cooling method. The four samples are subjected to Rockwell Hardness tester at four different elevated temperatures. The hardness of the specimen was investigated by the reinforcement of MgO. The maximum hardness was obtained at 12% of MgO. Similarly, the temperature was increased. Correspondingly the hardness of the specimen was also increased. The maximum hardness was obtained at 400ºC. The microstructure of the above mentioned four samples was evaluated by using scanning electron microscopy. The EDAX test revealed that Fe, Cu, Mg, Al, and Si, are present in the composite specimen. The EDAX test confirmed that the above metal matrix composite is aluminium based composite.