Fabrication and characterization of functionally graded aluminum/aluminum diboride matrix composites for high wear aerospace applications using centrifugal casting

Functionally graded advanced composite materials contain reinforcement particles whose volume fraction varies continuously thereby bearing a non-uniform microstructure with continuously changing properties. Aluminum-based functionally graded materials (FGMs) reinforced with AlB2 particles were manufactured by centrifugal casting to obtain these graded properties, which can not be achievable in monolithic or homogeneous materials. Volume fraction of pores and reinforcements particles, superficial Rockwell hardness (HR15w), Vickers microhardness (HV50), and stereological parameters from the microstructure were measured on Al -2 wt.% Mg - 1, 2, 3 and 4 wt.% B centrifugally cast and gravity cast composites. These materials showed AlB2 particles segregation toward the external zone of the cast piece, resulting in higher hardness and microhardness in this region. Wear behavior of the composites was studied by pin-on-disk wear test. This test was conducted on five zones (0, 5, 10, 15 and 20mm) sectioned along the length of the cylinder of the centrifugally cast aluminum matrix composites (AMC's) and on stationary (gravity) cast specimens. The results of this study showed the smallest wear volume on the external zone (20mm) of the FGMs. Morphological characterization of the wear tracks by scanning electron microscopy (SEM) helped corroborate the wear volume results.