Microstructure, elastic deformation behavior and mechanical properties of biomedical beta-type titanium alloy thin-tube used for stents

摘要

Cold-defonnability and mechanical compatibility of the biomedical beta-type titanium alloy are the foremost considerations for their application in stents, because the lower ductility restricts the cold-forming of thin-tube and unsatisfactory mechanical performance causes a failed tissue repair. In this paper, beta-type titanium alloy (Ti-25Nb-3Zr-3Mo-2Sn, wt%) thin-tube fabricated by routine cold rolling is reported for the first time, and its elastic behavior and mechanical properties are discussed for the various microstructures. The as cold-rolled tube exhibits nonlinear elastic behavior with large recoverable strain of 2.3%. After annealing and aging, a nonlinear elasticity, considered as the intermediate stage between "double yielding" and normal linear elasticity, is attributable to a moderate precipitation of a phase. Quantitive relationships are established between volume fraction of a phase (V-alpha) and elastic modulus, strength as well as maximal recoverable strain (epsilon(max-R)), where the epsilon(max-R) of above 2.0% corresponds to the V-alpha range of 3-10%. It is considered that the "mechanical" stabilization of the (alpha+beta) microstructure is a possible elastic mechanism for explaining the nonlinear elastic behavior. (C) 2015 Elsevier Ltd. All rights reserved.