HIGH-TEMPERATURE TENSILE PROPERTIES OF TI-15V-3CR-3SN-3AL ALLOY AND ITS MICROSTRUCTURAL CHANGES DURING THE DEFORMATION

Effects of an initial structure and deformation temperature on high temperature tensile properties of the Ti-15V-3Cr-3Sn-3Al alloy have been investigated by carrying out microstructural observations and tensile tests in a temperature range which is straddling the beta-transus temperature being about 1 015 K. The main results obtained can be summarized as follows. 1) The specimen which was in an as cold-rolled state showed a larger total elongation, in particular than other specimens in which recrystallizations had already been finished. 2) The initial microstructure of the specimen in the as cold-rolled state was seen to change, during tensile deformation below the beta-transus temperature, into a fine grained (alpha + beta) structure in which granular alpha-phases were uniformly dispersing. As the result, the total elongation and flow stress of the specimen deformed below the beta-transus temperature were found to be much more improved than those of the specimens already having fine recrystallized microstructures before heating to the test temperature. 3) The present experimental results suggest that the main deformation processes of this alloy at high temperatures would be both superplastic flow and dynamic recovery which would be accompanied by a continuous recrystallization.