Prediction of flow localization instability of TA15 titanium alloy with lamellar microstructure

Isothermal constant strain rate compression tests of TA15 titanium alloy with basketweave and Widmanstatten microstructure were carried out by a THERMECMASTOR-Z hot working simulation testing machine in the temperature range of 750-950°C and strain rate range of 0.001-10 s-1 in alpha and beta phase field. The corresponding microstructure of the compressed specimens was observed by metallographic and transmission electron microscopes. By using of flow localization instability parameter propounded by Jonas, the flow localization instability of TA15 titanium alloy with lamellar microstructure was predicted. The results indicate that flow localization instability of TA15 titanium alloy with basketweave and Widmanstatten microstructure both occurs in the low temperature (750-850°C) and high strain rate (0.1-10 s-1) regions and is observed mainly at the boundaries of prior beta grains. When the flow localization instability parameter is higher than 5, the flow localization instability of TA15 titanium alloy with Widmanstatten microstructure will take place. When it is higher than 7, the flow localization instability of basketweave microstructure will take place. The prediction of flow localization instability by Jonas flow localization instability parameter has to be further improved.