Superplastic forming Ti-6Al-4V titanium alloy cylinder with near uniform thickness distribution

Different shapes of pre-forming die were designed using MSC. MARC. The influence of surface friction of pre-forming die and final forming die on final thickness distribution was analyzed. The results show that the thinning of the blank near the periphery and the bottom of deep cylinder benefits to the uniform thickness. And higher friction coefficient of pre-forming die (0.57) can efficiently reduce the thickness of this regions and result in a more uniform final thickness distribution. Lower friction coefficient of forming die can make the sheet tend to integral formation, also results in uniform thickness distribution. The friction of pre-forming die is increased by machining and the friction of forming die is decreased by spraying BN ceramic powder. The aerospace Ti-6Al-4V deep cylinder with uniform thickness (1.50-1.78 mm) is fabricated successfully by using friction changing and direct-reverse superplastic forming method.