Superplasticity in Al–33Cu eutectic alloy in as extruded condition

Experiments were carried out to determine the superplastic properties of the Al–33Cu eutectic alloy in an as extruded condition. It is shown that the stress–strain curves do not attain a steady state condition and, except at high strain rates greater than ∼10⁻² s⁻¹, the curves show strain hardening due to concurrent grain growth. There is a sigmoidal relationship between stress and strain rate, with a maximum strain rate sensitivity of ∼ 0·5 at intermediate strain rates in region 2 and a decrease in the strain rate sensitivity to ∼ 0·3 at low strain rates in region 1. The maximum elongation to failure in these experiments is ∼1400% at an initial strain rate of 6·7 × 10⁻⁵ s⁻¹ and there is a decrease in the elongations to failure at both lower and higher strain rates. From detailed experimental measurements of grain growth, it is demonstrated by calculation that there is a genuine region 1 at low strain rates in this alloy in the as extruded condition.

MST/911