EFFECT OF THE UPSETTING TEMPERATURE ON THE ULTRAFINE-GRAINED TI ALLOY VT6

Abstract

The VT6 titanium alloy is widely applied as a structural material in aircraft engine building. Using severe plastic deformation (SPD) processing, high structural and performance properties are achieved in metals and alloys due to the nano- and ultrafine-grained (UFG) structural features. The present work examines the mechanical behavior and structural transformation of the UFG VT6 titanium alloy during experimental upsetting simulating the shape forming of parts of advanced gas-turbine engines. It was found that the formation of a UFG state in the VT6 alloy by equal-channel angular pressing (ECAP) reduced grain size to 0.6 μm and increased strength to 1200 MPa while preserving satisfactory ductility up to 11%. Further deformation of the alloy in a temperature range of 650 to 750 °С with a rate of 10–3s–1 preserved the alloy’s structure in a UFG range. With increasing deformation temperature, a considerable decline in the resistance to material flow was observed, which may be associated with an increase in the intensity of recrystallization processes. The strainrate sensitivity coefficient was calculated for upsetting at these temperatures, that showed the signs of superplasticity at these deformation regimes.