J. Mater. Sci. Technol. ›› 2019, Vol. 35 ›› Issue (3): 409-417.DOI: 10.1016/j.jmst.2018.10.003

• Research Article • Previous Articles     Next Articles

Effect of thermal annealing on the microstructure, mechanical properties and residual stress relaxation of pure titanium after deep rolling treatment

Jie Huanga, Kai-Ming Zhanga, Yun-Fei Jiaa, Cheng-Cheng Zhangc, Xian-Cheng Zhanga*(), Xian-Feng Mab*(), Shan-Tung Tua   

  1. aKey Laboratory of Pressure Systems and Safety, Ministry of Education, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai, 200237, China
    bSino-French Institute of Nuclear Engineering and Technology, SunYat-Sen University, Zhuhai, 519082, Guangdong, China
    cAECC Commercial Aircraft Engine Co. Ltd., Shanghai Engineering Research Center for Commercial Aircraft Engine, Shanghai, 201108, China
  • Received:2018-04-04 Revised:2018-05-07 Accepted:2018-05-09 Online:2019-03-15 Published:2019-01-18
  • Contact: Zhang Xian-Cheng,Ma Xian-Feng
  • About author:

    1 These authors contributed equally to this work.

Abstract:

The aim of this paper was to investigate the effect of thermal annealing on the microstructure, mechanical properties, and residual stress relaxation of deep rolled pure titanium. The microstructure and mechanical properties of the surface modified layer were analyzed by metallographic microscopy, transmission electron microscope and in-situ tensile testing. The results showed that the annealed near-surface layer with fine recrystallized grains had increased ductility but decreased strength after annealing below the recrystallization temperature, where the tensile strength was still higher than that of the substrate. After annealing at the recrystallization temperature, the recrystallized near-surface layer had smaller grain size, similar tensile strength, and higher proportional limit, comparable to those of the substrate. Moreover, the residual stress relaxation showed evidently different mechanisms at three different temperature regions: low temperature (T≤0.2Tm), medium temperature (T ≈ ( 0.2- 0.3)Tm), and high temperature (T ≥ 0.3Tm). Furthermore, a prediction model was proposed in terms of modification of Zener-Wert-Avrami model, which showed promise in characterizing the residual stress relaxation in commercial pure Ti during deep rolling at elevated temperature.

Key words: Deep rolling, Ultra-fine grain, Tensile strength, Microstructure, Residual stress