STA heat treatment of beta-titanium alloys after various thermomechanical processing

Commercial beta-titanium alloys are promising material fora wide range of applications due to essentially high strength/density ratio, sufficient fatigue performance and crack propagation resistance. Present work was aimed at systematical study the microstructure and mechanical properties of two commercial beta-titanium alloys VT22 and TIMETAL(R)-LCB in STA condition produced by special heat treatment, comprising from rapid heating into a single-phase beta field and subsequent aging, depending on previous thermomechanical processing employed. Three types of such a processing were studied: hot deformation at temperatures of alpha+beta field, hot deformation in single-phase beta field and cold deformation of as-quenched metastable beta phase. Solid solutionizing by rapid heating has proved to be efficient in receiving fine-grained beta microstructure with average grain size, which varies from 50 mum to 12 mum depending on initial microstructure. Such treatment allowed to obtain on subsequent aging yield strengths up to 1470 MPa while maintaining sufficient ductility.