Structure Evolution of Intermetallic Alloy VTI-4 during Inert Gas Quenching

Abstract

Samples of 0.6 mm thickness made from a VTI-4 alloy (Ti–21Al–23Nb–0.7Zr–1.4V–0.4Mo–0.31Si, at %) are treated by heating in the 850–950°C range, then continuously cooled in a gaseous atmosphere at rates close to 2.5 K/s and cold-rolled to a reduction degree of 60%. This study has established the cause of deterioration in the technological plasticity of samples heat-treated at 950°С upon cold rolling. Cracking during rolling is caused by the presence of fine O-phase precipitates formed during cooling in the structure. The heat treatment regime of the VTI-4 alloy, which provides sufficient technological plasticity for cold rolling to reduction degrees of at least 60%, together with vacuum annealing in the temperature range 850–900°С and cooling by purging with an inert gas at cooling rates higher than 2.5 K/s should be used.