Peculiar aging response of near β Ti-25 Nb-2Mo-4Sn alloy for biomedical applications

In this paper, aging response of a recently developed near beta Ti-25Nb-2Mo-4Sn (wt A) alloy with high strength and low modulus was investigated intensively. The experimental results from X-ray diffraction and transmission electron microscopy showed that the aging production of the Ti-2524 alloy was (beta+omega) or (beta+alpha) even under the same aging treatment condition, depending on the pre-treatments prior to the aging. Solid evidence confirmed the competition between stable alpha phase and metastable omega phase during the decomposition of beta phase on aging. Different aging response of Ti-2524 alloy can be attributed to high-density dislocations and grain boundaries which suppress the formation of omega, and alternatively promote alpha phase formation. This provides a thermo-mechanical approach to inhibit deleterious beta phase formation and assist fine alpha phase precipitation. Upon an appropriate aging treatment, superior mechanical properties of high ultimate tensile strength (1233 MPa) and low elastic modulus (77 GPa) were achieved in Ti-2524 alloy. (C) 2013 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.