Development of In-Situ Al-Si/CuAl2 metal matrix composites: Microstructure, hardness & wear behavior

In the present work, in-situ metal matrix composites were fabricated through squeeze casting by dispersing copper particles with different weight content (3, 6, 10, and 15%) into Al-12% Si piston alloy. Heat treatments at 380°C and 450°C for holding times of 6, and 18 hours were also performed. The microstructures, XRD, hardness and wear characteristics were evaluated. The results showed that the copper particles were reacted with the aluminum at all the processing conditions resulting in formation of fine copper aluminides intermetallics. Most of the intermetallics were CuAl2, while AlCu was appeared in small ratio. The intermetallics were homogenously distributed within the matrix up to 6 % Cu addition. The amounts of the resulted intermetallics were increased after performing heat treatment. At 380°C, most of the resulted intermetallics were CuAl2, while the Cu-rich intermetallics appeared at 450°C. Increasing the holding time to 18 hours resulted in grain coarsening and formation of some cracks. The hardness of the resulted composite materials was improved. The hardness value reaches to about 170 HV after heat treating at 380°C for 8 hours. The wear resistance of the resulted composite materials was remarkably improved especially at lower Cu addition and lower heat treatment temperature.