Superplastic characteristics of Ti-alloy and Al-alloy sheets by multi-dome forming test

Abstract

The present study evaluates the superplastic material characteristics of Ti-alloy "Ti-4.5Al-3V-2Fe-2Mo", SP-700, and Al-alloy "A5083", which have been obtained by utilizing a multi-dome forming test. First, the flow stress vs. strain rate relationship was established for certain strain rate range, from a single circular sheet containing four different domes, sized 35, 30, 25, and 20mm diameter, respectively. The multidome forming experiments were conducted under constant pressure at a superplastic temperature of 800°C for Ti-alloy and of 530°C for Al-alloy. The bulge forming of domes was also simulated by finite element method (FEM) to verify the experimentally-obtained material characteristics. Then the material characteristics obtained through multi-dome forming test were compared to those obtained by tensile step strain rate tests. In contrast to the predictions of the tensile test, the multi-dome forming test's predicted time of deformation was generally in reasonable agreement with the results of the FEM simulation. There was no great difference, however, between the multi-dome forming test and the tensile testing with regard to the predicted final thickness distribution.