A comparative study of the mechanical properties of high-strength β-titanium alloys

The mechanical properties of four commercial beta-titanium alloys (TIMETAL-LCB, Ti-15-3, beta-21S, and VT22) were compared in the solution-treated-and-aged (STA) condition following thermomechanical processing comprising beta solid solutioning, cold deformation (M), continuous rapid heating, and final aging. The peak temperature during the rapid heating step was chosen to obtain either a recovered or recrystallized condition and thereby to control the distribution of residual deformation defects, which in turn influenced the size and distribution of alpha precipitates in the final microstructure. It was established that a good balance of high strength (in excess of 1600 MPa) and reasonable ductility could be obtained if a fine-grain microstructure with a beta grain size of similar to 10 mu m was formed by recrystallization. The development of such a fine-grain size enabled a reduction in the aging temperature and thus increased the strength while maintaining ductility within the desired limits. In this respect, the properties could be varied to a great extent by varying the rate of heating to the aging temperature. On the other hand, aging of the recovered condition also led to a strength level of approximately 1600 MPa but with generally lower ductility than in the fine-grain, recrystallized condition. Another distinctive feature of the recovered condition was that the properties were relatively insensitive to the rate of heating to the aging temperature. (c) 2007 Elsevier B.V. All rights reserved.