Processing and properties evaluation of functionally continuous graded 7075 Al alloy/SiC composites

In the present investigation, functionally continuous graded AA 7075 Al/SiC composites (Al-6.5%SiC and Al-9.5%SiC) were processed through the centrifugal casting technique. Additionally, the as cast AA 7075 alloy was prepared for comparison purposes. The wear, hardness, strength and microstructure properties were characterized for the alloy and composites. The composites show clearly smooth and uniform SiC particles gradient from the core to the surface. The density of the composites decreases with the increasing particle volume fraction due to the increased defects. The improvement of hardness and wear resistance from the core to the surface of the FG composites is in accordance with the increasing amount of the particles. The wear rate of the FG composites increases with the increasing sliding speed, load and sliding distance conditions. Among the as cast alloy and the composites, the FG Al-9.5%SiC composite is found to be superior in terms of hardness and wear resistance. At low sliding speed (2 m/s) and load (15 N) conditions, the abrasive wear and matrix cracking are found to be dominant in contrast to the complex interaction of multi mode wear mechanisms such as tribo-oxidation, abrasive and delamination wear exist at higher load and speed conditions.