The Microstructure, Creep, and Tensile Behavior for Ti-5Al-45Nb (Atomic Percent) Fully-β Alloy

Abstract

The microstructure, tensile, and creep behavior of a Ti-5Al-45Nb (at. pct) alloy was evaluated. The main objective of processing and characterizing this alloy was to obtain the constituent properties of a fully-b Ti-Al-Nb alloy to aid in modeling the tensile and creep properties of twophase orthorhombic + body-centered-cubic (O + bcc) alloys. A second objective was to compare the tensile and creep behavior of this fully-b alloy to that for two-phase O + bcc alloys. This alloy exhibited a single-phase microstructure, containing the disordered bcc phase (b), after all the processing and heat treatments performed. This alloy was easily fabricated and workable; however, its creep resistance was significantly worse than that for fully-O and twophase O + bcc alloys. The alloy exhibited little strain hardening along with a room-temperature yield strength (YS) of 545 MPa, an ultimate tensile stress (UTS) of 559 MPa, a YoungÕs modulus (E) of 86 GPa, and a tensile elongation to failure of 25 pct. Extensive surface slip was evident on the deformed material. Its room-temperature tensile properties were quite similar to those for a fully-b Ti-12Al-38Nb microstructure (YS = 553 MPa, UTS = 566 MPa, E = 84, and e f > 27 pct). Thus, the room-temperature tensile properties and behavior of fully-b Ti-AlNb microstructures containing 50 at. pct Ti are not sensitive to compositional variations between 5 to 12 at. pct Al and 38 to 45 at. pct Nb.