The Studies of Continuous Cooling Transformation in Binary α+β and Metastable β Titanium Alloys

Abstract

The continuous cooling transformation diagrams of Ti-Cr, Ti-Mn, Ti-V and Ti-Mo alloys were plotted for investigations of ω phase in the cooling process of binary α+β and metastable β titanium alloys.
The supersaturated β phase decomposes with following processes for changing solute concentration and cooling rates, β0→βi+α'+ω(ω'), β0→βi+ω(ω'), β0→βi+α, where β0 represents β phase as solution treated, βi represents nonequilibrium β phase whose solute concentration changes with progress of decomposition and represents a pre-precipitation of ω phase.
The precipitation temperature of ω phase decreases with increace of cooling rates.
At the slower cooling rates α phase precipitates directly from β phase without precipitation of ω phase.
The range for precipitation of ω phase in the cooling process of binary α+β and metastable β titanium alloys by the electron concentration and cooling rates can be represented as a simple diagram. In conditions excluding this area it is possible to prevent precipitation of ω phase in the welded titanium alloys.