Fabrication of FGM sheet of aluminum matrix composite using powder metallurgy and hot-rolling processes

Nowadays, functionally graded materials have different applications in various industries, such as Aerospace industry, turbomachinery, coating industry, etc., due to their unique ability in providing multiple and sometimes opposite properties in a material volume. The purpose of this paper is to fabricate functionally graded material sheet of aluminum based composite with SiC reinforcing particles, using powder metallurgy and hot rolling methods. In this regard, the amount of reinforcement in the direction of thickness has been changed from the value of 0 to 4 weight percent. The samples were prepared in four steps including ball-milling, degassing, cold pressing and sintering, and then were hot-rolled up to three passes. The distribution of the reinforcing particles in the matrix phase was evaluated using optical microscope. Furthermore, the mechanical properties of the FGM samples including their hardness, tensile strength and flexural strength were measured and reported. Finally, the fracture surfaces in the tensile and flexural tests were observed using scanning electron microscope (SEM). According to the images obtained from the microstructure of the samples, the reinforcing particles have an acceptable distribution in the matrix phase. Also, the results indicate that the hardness and strength are enhanced by increasing reinforcing particles and the number of rolling passes. In addition, the main fracture mechanism in pure aluminum layer is the initiation and propagation of cracks between initial aluminum powder particles, while separation of two phases in the matrix-reinforcement interface and small SiC particle agglomerations are responsible for crack initiation in the composite layers.