Superplasticity of AlCoCrCuFeNi High Entropy Alloy

An AlCoCrCuFeNi high entropy alloy was hot worked by multi-directional isothermal forging at 950 degrees C to produce an equiaxed fine-grain structure with the average grain/particle size of similar to 1.5 mu m. The forged alloy exhibited superplastic behavior in the temperature range of 800-1000 degrees C. For example, during deformation at a strain rate of 10(-3) s(-1), tensile ductility increased from 400% to 860% when the temperature increased from 800 degrees C to 1000 degrees C. An increase in strain rate from 10(-4) to 10(-2) s(-1) T = 1000 degrees C did not affect tensile ductility and elongation to failure was about 800%. The strain rate sensitivity of the flow stress was rather high, m = 0.6, which is typical to the superplastic behavior. The equiaxed morphology of grains and particles retained after the superplastic deformation, although some grain/particle growth was observed.