Microstructure and mechanical property correlation and property optimization of a near β titanium alloy Ti-7333

As a newly developed near beta titanium alloy, knowledge on heat treatment associated microstructural evolution and its influence on mechanical properties has not yet been established for Ti-7333. Thus mechanical property potential of this alloy is not fully explored. In view of such a situation, a detailed study on heat treatment dependent mechanical property evolution and its correlation with microstructure was made in the present work with an aim to explore the optimum strength-ductility combination. The results show that the optimal combination of strength and ductility of Ti-7333 is realized with a mixed microstructure possessing globular/ellipsoidal alpha(p) (about 3% in volume fraction and about 1 mm in average particle size) and fine lenticular/acicular alpha(s) (about 30 nm in width and about 500 nm in length) distributed dispersedly in the beta matrix (about several microns in average grain size). With such a microstructure, an ultrahigh tensile strength (over 1400 MPa) with a reasonable ductility (over 10% in elongation) can be achieved. The corresponding heat treatment procedure is composed of a subtransus solution treatment at 820 degrees C for 50 min with air cooling plus an aging at 520 degrees C/540 degrees C for 6 h with air cooling. Compared with some other high strength Ti alloys (Ti-5553, Ti-1023, VT22, etc.), the newly developed Ti-7333 exhibits not only a more excellent strength-ductility combination but a more flexible heat treatment operation, rendering it more competitive. The results of the present work provide practical information for process optimization and to enrich the database of Ti alloys. (C) 2016 Elsevier B.V. All rights reserved.