Production and characterization of functionally graded Al2024/SiC composites prepared by powder metallurgy techniques.

In this study, functionally graded Al2024/SiC composites (FGMs) were produced by powder metallurgy method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDX) analyses indicated that Al and SiC were dominant components as well as others such as Al4C3, CuAl2, and CuMgAl2. A maximum bending strength of 1400 MPa was obtained for two layered FGMs which contained with 40 wt. % SiC on top layer. A decrease in microhardness and changes in porozity content were discussed in relation to the SiC content and the intermetallics formations. The results show that the increase in microhardness values and intermetallic formation play a major role on the improvement of mechanical properties of the composites. Al2024 alloy exhibited better toughness compared to those obtained from Al2024/SiC composites. The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5 % NaCl solution. Corrosion experiments shows that corrosion rate (1,109 mpy) of two layered FGMs which containing 50 wt. % SiC were much higher than Al2024 matrix (2,569 mpy) and Al2024/50 wt.% SiC composite (2,201mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disc wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role.