SPS has been utilized in several studies to retain the nanostructure of aluminum alloy powders during consolidation. Ye et al. investigated the effect of processing of cryomilled Al 5083 powder via SPS [13]. X-ray Diffraction (XRD) grain size calculations before and after SPS showed that the average grain size of the alloy only increased from 25nm to 50nm (from powder to bulk state). Subsequently, the hardness values obtained through nanoindentation for specimens of AA5083 produced via SPS were highly improved in comparison to conventional sintering methods were grain coarsening takes place on a larger scale. In another study the combination of cryomilling and SPS of AA-5356/B4C nanocomposites powder was found to largely improve the microhardness and flexural strengths of the bulk nanocomposite. Rana et al. [14] investigated the effect of SPS on mechanically milled AA6061 (Al–Mg–Si) micro-alloy powder. The average grain size after 20h of milling was ∼35nm and increased to only ∼85nm after processing with SPS at 500°C. Microhardness and compressive tests were carried out on the consolidated near full density specimens of both unmilled and milled powders and the results showed significant increase in both hardness and compressive strengths for the milled nanocrystalline powders as a result of the very fine grain size.
