Experiments and modeling of spark plasma sintered, functionally graded boron carbide–aluminum composites

Continuous functionally graded boron carbide aluminum cermets were created using spark plasma sintering. The B 4C compacts with large, precipitous density gradients were melt infiltrated with 99.999% Al at 1453 K for 10 min. The microstructure of the material exhibits a gradual change from fully dense B 4C with a nominal grain size of 2 μm and a hardness of 32.3 GPa to a B 4C–Al cermet with a B 4C grain size on the order of 200 nm and a hardness of 8.36 GPa. Prior to melt infiltration, X-ray diffraction data indicates that the B 4C compacts have some microstructural defects present. This result is confirmed by the presence of twins on the fully dense fracture surface. Following melt infiltration, X-ray diffraction reveals that some of the defects are dissipated and small amounts of Al 3BC are present. Numerical modeling results indicate the presence of a 405 K temperature difference between the top and bottom of a specimen using this method and help confirm experimental observations.