Superplastic behaviour of an Al–Li–Cu–Mg alloy

Abstract

The superplastic properties and microstructure evolution of an Al–Li–Cu–Mg alloy were examined in tension in the temperature interval 400–525°C at strain rates ranging from 1·4 × 10⁻⁴ to 5·6 × 10⁻² s⁻¹. The refined microstructure with an average grain size of about 11 μm was produced in thin sheets by a thermomechanical processing. A maximum elongation to failure of 960% appeared at a temperature of 475°C and an initial strain rate of 1·4 × 10⁻³ s⁻¹, with corresponding strain sensitivity coefficient m of about 0·58. The highest m value was approx. 0·64 at the similar strain rate and T=525°C (δ≈750%). The microstructural evolution during superplastic deformation of the Al–Li–Cu–Mg alloy has been studied quantitatively. The role of dispersoids in superplasticity is considered.