Acta Metallurgica Sinica (English Letters) ›› 2022, Vol. 35 ›› Issue (5): 839-852.DOI: 10.1007/s40195-021-01293-3

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Microstructural Evolution and Anisotropic Weakening Mechanism of ZK60 Magnesium Alloy Processed by Isothermal Repetitive Upsetting Extrusion

Zhengran Liu1, Xi Zhao1(), Kai Chen1, Siqi Wang1, Xianwei Ren2, Zhimin Zhang2, Yong Xue2   

  1. 1School of Mechanical and Electrical Engineering, North University of China, Taiyuan, 030051, China
    2Engineering Technology Research Center for Integrated Precision Forming of Shanxi Province, North University of China, Taiyuan, 030051, China
  • Received:2021-05-18 Revised:2021-06-07 Accepted:2021-06-08 Online:2021-08-16 Published:2021-08-16
  • Contact: Xi Zhao
  • About author:Xi Zhao, zhaoxi_1111@163.com

Abstract:

The isothermal repetitive upsetting extrusion (RUE) was implemented to process ZK60 magnesium alloy at 380 °C. Then, the relationship between the microstructural characters, including grain refinement and texture evolution, and the mechanical performance of the alloy was investigated. Results showed that after 3 passes of RUE, the average grain size was refined from 115.0 to 26.5 μm, which was mainly caused by the continuous dynamic recrystallization and discontinuous dynamic recrystallization. Meanwhile, the elongation of the alloy increased from 13.8 to 21.6%, and the superplasticity (142%) of the alloy has been achieved in the following high temperature tensile test, which is very beneficial for the further processing of the alloy into components. In particular, the alloy formed a distinctive texture distributed between < 2-1-11 > and < 2-1-14 > , which was greatly related to the Schmid factor of extrusion direction (ED) and transverse direction (TD). This texture changed the initiation ability of basal and prismatic slip in both directions and inhibited the initiation of partial tensile twinning in TD; thus, the anisotropy in both directions was weakened. As expected, the tensile yield strength difference decreased from 25.9 to 3.4 MPa, but it was used as the cost of tensile yield strength in ED.

Key words: Severe plastic deformation, Repetitive upsetting extrusion, ZK60 alloy, Microstructure, Mechanical properties