Post-Superplastic Forming Analysis Under Different Loading Paths. Part One: Uniaxial Loading Case

Abstract

In a previous work, an optimization approach for superplastic forming based on a multiscale stability criterion, and yielding a variable strain rate loading path instead of the commonly used constant strain rate one, was presented. The approach was experimentally validated using the AZ31 magnesium alloy, where it was proven effective in reducing forming time without sacrificing the uniformity of deformation. In this work, the validation process is taken to a different level, where the post-superplastic forming mechanical properties, often ignored in superplasticity, become the criteria. The material is first superplastically deformed under uniaxial loading at an elevated temperature, following both loading paths; constant strain rate versus optimized variable strain rate. Thereafter, specimens extracted from the deformed material are tested at room temperature to evaluate the changes in mechanical properties, in reference to those of the as-received material. The results emphasize on the necessity of a combined forming and post-forming analysis in optimizing the superplastic forming process.