Abstract
New strain rate sensitivity factors α and γ values have been defined respectively as power indices of changing rates of depth and diameter of hollows obtained by high temperature indentation test, and examined to evaluate superplasticity in the 7475 aluminum alloy sheet. The α and γ values for this alloy are proportional to each other and show the same tendency as the ordinary m value and total elongation. The values themselves are a little larger than that of m. Though the m-value and total elongation of the tested sheet are found to be small, the α and γ values are predictive of the deformation behaviour.
