The Difference between Hot and Cold Deformation and its Effect on Microstructure and Mechanical Properties of Near Beta Titanium Alloy

Abstract

An investigation of cold and hot deformation and the subsequent heat treatment including the annealing at the (α+β)- field temperature and ageing of VST55531 alloy showed that the material after the cold drawing without the heat treatment has the extremely low values of uniform elongation and during the tensile test the strain becomes localized at a neck upon 0.2 % strain. The ageing of coldworked material improves the strength and increases a limit of uniform deformation and generally has a beneficial effect on a strengthto-ductility ratio of alloy probably due to achieving a special morphology of secondary α-phase. The obtained values of the combination of strength and ductility in the cold-worked material at 50% strain reduction degree are 1 625 MPa for UTS, 8% - El, 36% - RA, that exceed significantly the values obtained for the hot-worked and as-annealed material, and are attractive for application in products that require the increased strength and ductile characteristics.