Influence of cooling rate on ω phase precipitation and deformation mechanism of a novel metastable β titanium alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-01, Vol.829, p.142151, Article 142151
• Main Authors: Wang, Kaige, Wu, Di, Wang, Dong, Deng, Zixuan, Tian, Yueyan, Zhang, Ligang, Liu, Libin
• Format: Article
• Language: English
• Subjects: Air cooling; Beta phase; Chemical precipitation; Cooling effects; Cooling rate; Deformation; Deformation mechanism; Deformation mechanisms; Ductility; Iron; Mechanical properties; Microstructure; Phase composition; Phase transitions; Slip; Solution heat treatment; Tensile strength; Titanium alloys; Titanium base alloys; Transmission electron microscopy; Water quenching; β titanium alloy; ω phase
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2021.142151

This work investigated the effect of cooling rate (water quenching and air cooling) on the precipitation of ω phase after solution treatment in β-phase region, and its effect on the mechanical properties in a novel metastable β titanium alloy (Ti–5Mo–3Cr–Fe–3Zr). The initial microstructures, phase composition and deformation-induced microstructures have been investigated using SEM, EBSD, XRD, and TEM. The phase composition of water-quenched alloy and air-cooled alloy are β, α", and ω phase. The size and volume fraction of ω phase of air-cooled alloy are larger than that of water-quenched alloy, resulting in an increase in tensile strength and a decrease in ductility. Deformation mechanisms of Ti–5Mo–3Cr–Fe–3Zr alloy with different cooling rate change from stress-induced ω phase transformation and dislocation slip to only dislocation slip. The stress-induced ω lamellas parallel to [1-11]β direction along the [0001]ω1 direction, which is formed by {112}β β slip. Dislocations can cut through the encountered ω phase to form ω-free deformation bands, which accounts for the ductility. •The size and volume fraction of ω phase of air-cooled alloy are larger than that of water-quenched alloy.•Deformation induced β to ω phase and ω to β phase transformation simultaneously appear in water-quenched alloy.•Dislocations can cut through the encountered ω phase to form ω-free deformation bands, which accounts for the ductility.