Hot Stretch Bending and Creep Forming of Titanium Alloy Profile

Abstract

Titanium alloy is frequently used in aerospace applications such as load carrying airframe due to their excellent mechanical and corrosion properties in combination with being comparatively light weight. However, it is well-known that titanium alloy is difficult to form at room temperature. So hot stretch bending and creep forming process is used to improve formability and reduce springback in forming titanium alloy profile. The principle of hot stretch bending and creep forming is leading a stress relaxation stage by maintaining the workpiece against the die for a selected dwell time after hot stretch bending stage. This allows the benefits of low residual stress and minimum springback including inexpensive tooling and good repeatability. In the present work, a set of uniaxial tension tests was performed on OT4 titanium alloy at the temperature ranging from 773K to 973K and strain rate from 0.0025 s-1 to 0.01 s-1. Stress relaxation tests were carried out at the temperature range from 773K to 973K. Arrhenius model was employed to characterize the creep behaviour. Finite element model of hot stretch bending and creep forming process was created in ABAQUS. The results of FE simulation indicate that residual stress decreases greatly in stress relaxation stage and low residual stress lead smaller springback. The predicted springback show promising agreement with the corresponding experimental observations.