Superplasticity at High Strain Rates: Exploring the Potential of a New Eutectic High-Entropy Alloy

This study investigates the high-temperature deformation behavior of a fine-grained AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA). AlCoCrFeNi 2.1 EHEA exhibited remarkable superplasticity at high strain rates, achieving ~960% elongation at 900 °C and 10 -1 s -1 . Optimal superplasticity is observed at a strain rate sensitivity (m) of ~0.5, with transitions to non-superplastic behavior both at low and high strain rates. The influence of strain rate (3x10 -4 s -1 to 10 -1 s -1 ) and temperature (700 to 900 °C) on ductility and ‘m’ is significant with a combination of high temperature and high strain rate showing exceptional superplasticity. Grain boundary sliding appeared to be the dominant mechanism, which was facilitated by the retention of an equiaxed grain structure. Fractured samples revealed cavities of 1-5 μm, suggesting nucleation, but growth was limited by a plasticity-driven mechanism proportional to cavity size. These findings highlight the potential of this EHEA for high-temperature applications.