Low-Temperature Coarsening and Plastic-Flow Behavior of an Alpha/Beta Titanium Billet Material With an Ultrafine Microstructure

摘要

The influence of microstructure evolution on the low-temperature superplasticity of ultrafine alpha/beta titanium alloys was established. For this purpose, the static and dynamic coarsening response and plastic-flow behavior of Ti-6A1-4V with a submicrocrystalline microstructure were determined via a series of heat treatments and uniaxial compression tests at temperatures of 650, 775, and 815 degrees C at all test temperatures, static coarsening exhibited diffusion-controlled kinetics and followed a dependence on phase composition and volume fraction qualitatively similar to previous observations at 850 to 950 degrees C. Dynamic coarsening at 775 and 815 degrees C and strain rates was similar to prior higher temperature observations as well in that the kinetics were approximately on order of magnitude faster than the corresponding static behaviors. The increase in coarsening rate with superimposed deformation was attributed to the enhancement of diffusion by dislocations generated in the softer beta phase.