Development of hardness homogeneity and superplastic behavior in an aluminum–copper eutectic alloy processed by high-pressure torsion

An Al–33% Cu eutectic alloy was processed by high-pressure torsion (HPT) at a pressure of 6.0 GPa for 1/4 to 10 turns. Examination after processing showed a gradual evolution to a reasonable level of hardness and microstructural homogeneity after 5 or more turns. Tensile tests were conducted at a temperature of 723 K on specimens processed through 5 and 10 turns of HPT. These specimens exhibited excellent superplastic properties with a maximum elongation of ∼1250% at strain rates lower than 10−3 s−1. The results also showed that the maximum elongation is displaced to a faster strain rate when the HPT processing is conducted to a higher number of turns. An analysis demonstrates that superplastic flow in the Al–Cu alloy processed by HPT is well described by a theoretical relationship that was developed for conventional superplastic materials.