Superplastic Zinc-Aluminum Alloys in Automotive Applications 700133

Three ranges of zinc-aluminum alloys, (1) 88 wt.% Zn, 12 wt.% Al;(2) 78 wt.% Zn, 22 wt.% Al; and (3) 30 wt.% Zn, 70 wt.% Al, with copper, magnesium and manganese additions up to 3.0, 1.0, and 0.2 wt.%, respectively, were investigated. A thermal decomposition method of obtaining a fine microstructure to achieve “Superplasticity” is presented. The effects of alloying element additions, solidification rates (graphite mold versus sand versus continuous casting), annealing time (up to 72 hr), aging time and temperatures (75 F, 20 hr and 200 F, 2 hr), and mechanical working were determined. Correlations between these effects were made with reference to current metal deformation theories aided by electron microscopic studies, x-ray micro-probe and computer analysis.

A closed-die forming process was achieved and demonstrated, using alloys and heat treatment cycles developed in this study.