Effect of extrusion and rotary swaging on the microstructural evolution and properties of Mg-5Li-5.3Al-0.7Si alloy

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  • Hao Chen
  • Meng Zhang
  • Fanxiao Kong
  • Bin Li
  • Xiaofei Cui
  • Yuanding Huang
  • Norbert Hort
  • Regine Willumeit-Römer
  • Weidong Xie
  • Guobing Wei

High-strength Mg–5Li-5.3Al-0.7Si alloys were prepared by applying a combination of conventional extrusion with an extrusion ratio of 25:1 at 320 °C and subsequent rotary swaging (RS) with 0.2 mm reduction per pass in diameter at room temperature. The microstructural evolution was characterized and mechanical properties were investigated by tensile tests. The EBSD results showed that the grain size of the alloy decreased remarkably after extrusion and RS. Meanwhile, the yield strength (YS) of the as-extruded alloy was significantly improved from 161 MPa to 301 MPa by 2 passes RS, with only a slight reduction in ductility. The grain refinement during RS should be attributed to the activation of twins and continuous dynamic recrystallization (CDRX). The texture evolution during RS was investigated by EBSD. The number of grains with <0001> parallel to extrusion direction (ED) decrease significantly after RS. These grains are subjected to multi-directional stress and deformation, which rotate and develop a stronger texture component with <101‾0> - <112‾0> parallel to ED during RS, leading to the optimization of grain orientation. The phase evolution was investigated by SEM, EDS and TEM. Extrusion and RS effectively crush and disperse the second-phase particles of Mg2Si and Al0.89Li0.11, leading to their homogenization and refinement. The main mechanisms for strengthening the as-swaged alloy include grain refinement strengthening, dislocation strengthening, and second-phase strengthening. Grain refinement strengthening plays a dominant role in the as-swaged alloy.

Original languageEnglish
Article number145627
JournalMaterials Science & Engineering A
Publication statusPublished - 03.10.2023
Externally publishedYes

Bibliographical note

Funding Information:
The authors are grateful for the financial supports from the National Key R&D Program of China through Grant 2021YFB3701100 , the National Natural Science Foundation of China (No. 52271091 ) and the China Scholarship Council (Grant No: 202206050135 ).

Publisher Copyright:
© 2023 Elsevier B.V.

    Research areas

  • Conventional extrusion, Mg-Li alloy, Microstructural evolution, Rotary swaging, Strengthening mechanism
  • Engineering