Microstructure evolution and mechanical property of a new multi-component beta titanium alloy with ultrahigh strength above 1350 MPa

The microstructure evolution and precipitation behavior of a multi-component b titanium alloy (namely TB17) were investigated through various characterization methods. The results show that with the increase of the solution temperature, the coarse lamellar alpha phase (alpha(l)) and fine secondary a phase (alpha(s)) existed in the original as-forged TB17 alloy decrease. At the same time, the molybdenum equivalent value of the b matrix also decreases gradually, leading to the increase of alpha(s) phase during the following aging process. For the aged samples, the micro-strain accumulated in the beta matrix resulted from phase transformation strain exhibits an increasing trend as the solution treatment temperature rises, highly depending on the volume fraction of alpha(s) phase. When the alloy is subjected to a solution treatment at temperature of 805 degrees C plus aging, it can achieve a good combination of high strength of 1375 MPa and considerable ductility due to mixed microstructure of suitable amount of micro-scale alpha(l) and nano-scale alpha(s) precipitates. The strength is further improved by increasing the solution temperature (from alpha+beta to beta field), which is attributed to higher volume fraction of fine alpha(s) precipitates formed during aging that can effectively hinder dislocation slip and induce micro-strain. Morphological features of the fracture surfaces are also discussed against the different microstructural morphologies, revealing the fracture mechanism of TB17 alloy under different heat treatment conditions. The current work could contribute to a better understanding of phase transformation behavior and strengthening mechanism in TB17 alloy. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).