High-strain-rate deformation of pure aluminum reinforced with 25% alumina submicron particles near the solidus temperature

Discontinuously reinforced aluminum metal matrix composites (MMCs) with about 20 vol.% reinforcement produced by powder metallurgy (PM) are attractive for many structural applications because of their high specific strength and stiffness. While they exhibit reduced ductility and toughness at room temperature, many of them can be superplastically deformed at high-strain rates in the vicinity of their solidus temperature [1-8]. Recently, the mechanical properties at room and elevated temperatures of dispersion-strengthened-cast aluminum (DSC-Al) with high volume fractions (>25 vol.%) of submicron Al2O3 oxide dispersoids have been investigated [9,10]. The material has characteristics of both Al-MMCs (e.g., high modulus, strength, and low coefficient of thermal expansion) and conventional PM oxide-dispersion-strengthened aluminum with lower reinforcement content (e.g., high creep resistance). While the room-temperature ductility of DSC-Al is quite high (9.4% for extruded DSC-AI with 25 vol.% Al2O3 oxide particles [9]), its formability at elevated temperatures is limited by its high creep strength and low creep ductility [10,11]. Because of the similarity of microstructure between DSC-Al and other Al-MMCs, the question arises whether DSC-Al containing 25% Al2O3 particles can exhibit high-strain-rate superplasticity near the solidus temperature. The purpose of the present note is to investigate this issue.