Developing superplasticity in an aluminum matrix composite processed by high-pressure torsion

An Al-7075 alloy reinforced with 10 vol% Al2O3 particulates was processed by high-pressure torsion (HPT) at room temperature under a pressure of 6.0 GPa through up to 20 turns. The metal matrix composite (MMC) showed significant grain refinement from an initial average grain size of ~8 μm to ~300 nm after processing by HPT through 20 turns. The Vickers microhardness also increased from an initial value of Hv≈167 to a saturation value after HPT processing of Hv≈260. Tensile testing at 623 K demonstrated the potential for achieving true superplasticity in the HPT-processed MMC with a maximum elongation of ~670% when testing at a strain rate of 1.0×10−2 s−1.