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 B4C 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 B4C with a nominal grain size of 2 μm and a hardness of 32.3 GPa to a B4C–Al cermet with a B4C 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 B4C 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 Al3BC 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.