Simultaneous improvement in strength and ductility of CT20 titanium alloy at cryogenic temperature

• Published in: Materials & design 2023-11, Vol.235, p.112416, Article 112416
• Main Authors: Zhang, Runqi, Zhao, Qinyang, Guo, Dizi, Du, Yu, Zou, Lei, Ying, Yang, Zhang, Bingjie, Zhao, Yongqing
• Format: Article
• Language: English
• Subjects: Cryogenic temperature; CT20 alloy; Deformation mechanisms; Tensile properties; Twinning
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2023.112416

[Display omitted] •The CT20 alloy with a special texture shows simultaneous improvement in strength and ductility at cryogenic temperature.•More twin types are activated at 77 K and continuous formation of twin boundaries causes the dynamic Hall-Petch effect.•The //ND texture and strong TWIP effect cause excellent ductility at cryogenic temperature.•Cryogenic temperature changed the locations of crack initiation in CT20 alloy with equiaxed microstructure. Quasi-static tensile deformation behaviors at room temperature (RT) and 77 K of the CT20 alloy with a //ND texture were investigated. The CT20 alloy with equiaxed microstructure exhibits excellent mechanical properties with simultaneous increase in strength and elongation at cryogenic temperature. In current study, the initial //ND texture promotes basal slip actuation effectively and continuously increases Schmid factor (SF) of other slip systems to promote multiple slip. Cryogenic temperature weakens the deformation texture due to the promotion of multiple slip. Since the decrease of the stacking fault energy (SFE), more twins in number and variety nucleate at 77 K and promote multiple slip. It causes strong cryogenic twinning-induced plasticity (TWIP) effect. Grain refinement induces strong cryogenic dynamic Hall-Petch effect resulting in high strain-hardening rate (SHR) and strength. The yield strength (YS, ∼1052.67 MPa), ultimate tensile strength (UTS, ∼1102.51 MPa) and elongation (EL, ∼21.1 %) of the 77 K specimen are about 84.1 %, 69.1 % and 38.8 % higher than its counterpart at RT, respectively. In addition, cryogenic temperature changes the initiation location of cracks and promotes cracks initiation at grain boundaries homogeneously.