Effect of aging temperature on microstructure and mechanical properties of a novel Ti-6121 alloy

• Published in: Journal of alloys and compounds 2023-06, Vol.947, p.169612, Article 169612
• Main Authors: Chen, Jianwei, Wang, Le, Fan, Qunbo, Sang, Zhuoyue, Xu, Yao, Wang, Changhao, Yao, Jiahao, Zhou, Zhiming, Yang, Liu, Liu, Zheng, Gao, Jinliang, Feng, Heyong
• Format: Article
• Language: English
• Subjects: Heat treatment; Microstructure evolution; Multi-scale microstructure; Strength-ductility combination; Tensile properties
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2023.169612

The effect of heat treatment on the microstructure and mechanical properties of a novel α + β Ti-6.2Al-0.8V-2.25Mo-1.2Cr-0.5Si (wt%) alloy was investigated in this paper. Microstructure and crystalline structure of the alloys after different solution and aging treatments were identified by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that a multi-scale microstructure was possessed in the heat-treated samples, which was composed of equiaxed primary α (αp) phase and nano-scale acicular secondary α (αs). After 900 ℃ solution for 1 h and 550 ℃ aging for 6 h, the alloy exhibited the optimal combination of strength and ductility (the ultimate tensile strength of ∼1387 MPa, the elongation of ∼11 %). Furthermore, the combination mechanism of strength-ductility of the sample under this condition was investigated. The samples before and after tensile fracture were analyzed using transmission electron microscope (TEM) and electron back-scattered diffraction (EBSD). The results showed that a large proportion of nano-scale acicular αs phases precipitated from the β matrix can effectively prevent the slip of dislocations and enhance the strength of the alloy. In addition, the multi-scale microstructure can create the strain partition, which can mediate the strain incompatibility between the αp and the transformed β (βT) to obtain an excellent combination of strength and ductility. •The heat-treated Ti-6121 alloy exhibits the ultimate tensile strength of ∼1387 MPa and the elongation of ∼11 %.•The ultrahigh tensile strength (1463 MPa) of Ti-6121 alloy should be mainly caused by the dense nano-scale acicular αs.•The outstanding combination of strength and ductility of Ti-6121 alloy should be attributed to the multi-scale microstructure.