MICROSTRUCTURAL EVOLUTIONS OF DIFFERENT T I-6-PERCENT AL-4-PERCENT-V TITANIUM-ALLOY MORPHOLOGIES DURING AND AFTER HOT-WORKING SIMULATED BY TORSION TESTING

The microstructural evolutions of the Ti - 6 % Al - 4 % V titanium all oy were studied using light-optical microscopy, scanning electron micr oscopy and in transmission on hardened states, deformed using a torsio n bench between 800 and 1200-degrees-C, for deformation speeds include d between 10(-5) and 10 s-1. Several initial morphologies, at ambient temperature. either <<equiaxial>> or <<needle-shaped>> or <<spaghetti- shaped>> were studied. The alpha and beta phases show the various dyna mic behaviors. The alpha phase, especially when it is <<needle->> or < <spaghetti->> shaped, is refined by fragmentation, while in the initia l <<equiaxial>> shape it is not refined in the considered areas of def ormation speed and temperature. However, this phase recrystallizes by growth due to sliding of the grain boundaries in the superplastic area . The beta phase is the seat of refining by continuous dynamic recryst allization The effects of static recrystallization treatments are ment ioned.