The use of microstructural gradients in hot gas-pressure forming of zn-ai sheet

The gas-pressure forming of Zn-22 pct Al sheet containing regions of different initial microstructure, introduced by selected-area heat treatment, at elevated temperature and low strain rates has been evaluated. The heat treatments used converted a fine, spheroidal, phase mixture into a lamellar one, and the fraction of transformed material could be controlled reasonably well. The mechanical response of the material, determined by tensile testing, was correlated with the microstructure and its evolution during deformation. The material behavior was formalized as a simple constitutive equation which was used in finite-element modeling of the forming process. It was possible to influence the thickness distribution of a formed shape in a controlled manner using this approach.