Synthesis and consolidation via spark plasma sintering of nanostructured Al-5356/B4C composite

The combination of two versatile processing routes: cryomilling and spark plasma sintering (SPS) was employed in the present study for fabrication of bulk Al5356-B4C nanocomposites. This approach resulted in large microhardness and flexural strengths values in the consolidated samples of 244 ± 2.06 HV and 707 MPa respectively. While cryomilling provided the combined advantage of homogenous dispersion of the reinforcement in the matrix as well as nanostructuring of the Al-5356 phase, the SPS facilitated the solid state consolidation of the metal matrix composite (MMC) in one single step at very high sintering rates and very short dwelling times. No additional processing steps such as forging or hot extrusion were necessary to achieve powder consolidation. The resulted samples exhibited two to three times higher microhardness values than the monolithic micron sized un-reinforced alloy.

► Full density (>99%) was obtained for this system above 500 °C.
► Maximum strength of 707 MPa and hardness of 244 HV for a grain size of 67 nm.
► Analysis of the fracture surface showed dimples within the matrix.
► The grain size varies between 1 and 5 min holding for the same sintering temperature.