Superplastic forming of 7475 al alloy by variable-pressure blowing

Abstract

Although the bulge forming technique is currently employed in commercial superplastic forming (SPF) processes, the uniaxial tensile test is still the most commonly used method for the evaluations of the superplasticity of materials due to its simplicity in testing. The bulge forming of domes is usually involved in the early stages of superplastic forming processes and hence attracted many research attentions. In this study the superplastic bulge forming of 7475 Al alloy by the constant-pressure blowing and the constant strain rate variable-pressure blowing were studied. In addition, a step-change pressure forming process to shorten the forming time spans required for specific amounts of forming strain by several easy step changes of forming pressure were proposed and examined. The purpose of this work is to characterize the forming behaviors of 7475 Al alloy by these forming processes and to compare the forming efficiency of variable-pressure forming processes to those of constant-pressure forming ones.