Formability Determination of Titanium Alloy Tube for High Pressure Pneumatic Forming at Elevated Temperature

Abstract

High pressure pneumatic forming is a forming technology at elevated temperature, whose ultimate goal is to form a tube blank of usually uniform cross-section into a die cavity of complex shape with variable cross-sections by applying internal pressure and axial feeding. In this paper, the mechanical property and formability of Ti-3Al-2.5V were evaluated by tube bulging tests at 800°C. The limit expansion ratios of Ti-alloy tube were 56.1%, 43.3% and 34.2% with constant internal pressure of 7.5, 12 and 14M Pa, respectively. The outline of the bulging zone was considered as a parabolic model. The relationship between thickness at the highest position and bulging height was considered as a linear model. The Fields–Backofen constitutive model was used to describe the flow stress of Ti-3Al-2.5V under biaxial stress states.