Microstructure, mechanical properties and fracture mechanism of TC32 titanium alloy with different heat treatment processes
Li Mingbing, Wang Xinnan, Shang Guoqiang, Zhu Liwei, Li Jing, Li Xing, Zhu Zhishou
2021, 46(4):
112-117.
doi:10.13251/j.issn.0254-6051.2021.04.019
Abstract
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Effect of two heat treatment processes, which were normal annealed (700 ℃ for 2 h, AC) and double annealed (880 ℃ for 2 h, AC and 550 ℃ for 6 h, AC), on microstructure and mechanical properties of the new high-performance and low-cost TC32 titanium alloy was studied by using optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile testing machine. The results show that after normal annealing, the content of primary α phase is about 37.2%, and a slight spheroidization occurres, the β-transformed matrix is composed of coarser lamellar secondary α phase and residual β phase. The average ultimate strength (UTS) under this process is 939 MPa, and the average elongation (EL) is 17.4%. After double annealing, volume fraction of primary α phase which occurred recrystallization is about 11.8%, and β-transformed matrix is composed of fine lamellar secondary α phase with weaving basket-weave structures. The average ultimate strength (UTS) under this process is 1258 MPa, and the average elongation (EL) is 9.4%. Fracture morphologies show that the tensile fracture mechanism of both processes belongs to ductile fracture. The fracture characteristics of normal annealed have larger fibrous and shear lip zones, no obvious radical zone, and more equiaxed dimples with larger in size and deeper in depth. The fracture characteristics of double annealed have a certain area of radical zone, in addition to the equiaxed dimples, a number of tearing edges is observed.
