A Short Review on Superplasticity of Aluminum Alloys

Superplastic aluminum (Al) alloys can be used in the forming processes to fabricate complex geometry components for a wide range of applications in the automobile industry, where light weight and high stiffness are needed. Those alloys exhibit extreme tensile elongation of more than 300% at a high homologous temperature and appropriate low strain rate. Superplasticity occurs in Al alloys via the mechanisms of grain boundary sliding, solute drag creep and diffusion creep. Grain boundary sliding usually leads to extensive superplasticity. The activation of grain boundary sliding depends on grain size, strain rate sensitivity, deformation temperature and alloy chemical composition. A complete understanding of influencing factors on Al alloy superplasticity is the key to developing novel superplastic Al alloys. This review discusses the superplastic behavior of several Al alloys, especially focusing on Al-Mg 5xxx alloys. It highlights the mechanisms that govern superplasticity of Al alloys at a low and high strain rate. The factors which influence superplasticity are analyzed. As practice industrial applications, high-cycle-time superplastic forming operations such as quick plastic forming and high-speed blow forming are briefly discussed.