Behavior of Titanium Alloy under Uniaxial and Biaxial Superplastic Conditions

摘要

The validity of extending constitutive relationships established under uniaxial condition to biaxial forming is an important issue from both basic and applied perspectives. The deformation of titanium alloy is studied under both uniaxial and biaxial states of stress to understand this relationship. Based on the mechanical constitutive equation obtained from uniaxial test, a model based on finite element method (FEM) was established to predict the superplastic deformation (SPD) of biaxial cones. The cones are designed to be subjected to balanced biaxial state of stress under a constant pressure loading. In the multi-cone test, four cones of different diameters are concurrently formed when they are subjected to different biaxial strain rate conditions. Sensitivity of material parameters obtained under uniaxial conditions are critically examined. Thickness profile and metallurgical state of the cones are also analyzed.