J. Mater. Sci. Technol. ›› 2021, Vol. 84: 27-42.DOI: 10.1016/j.jmst.2020.12.047

• Research Article • Previous Articles     Next Articles

Origins of high ductility exhibited by an extruded magnesium alloy Mg-1.8Zn-0.2Ca: Experiments and crystal plasticity modeling

Jie Wanga,b, Gaoming Zhua, Leyun Wanga,e,**(), Evgenii Vasilevb, Jun-Sang Parkc, Gang Shad, Xiaoqin Zenga,e,**(), Marko Knezevicb,*()   

  1. aNational Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai, 200240, China
    bDepartment of Mechanical Engineering, University of New Hampshire, Durham, NH, 03824, USA
    cAdvanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
    dSchool of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
    eState Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China
  • Received:2020-10-07 Revised:2020-12-12 Accepted:2020-12-24 Published:2021-09-10 Online:2021-02-01
  • Contact: Leyun Wang,Xiaoqin Zeng,Marko Knezevic
  • About author:* E-mail addresses: marko.knezevic@unh.edu (M. Knezevic).
    xqzeng@sjtu.edu.cn (X. Zeng),
    ** National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai, 200240, China.E-mail addresses: leyunwang@sjtu.edu.cn (L. Wang),

Abstract:

Low ductility and strength are major bottlenecks against Mg alloys’ wide applications. In this work, we systematically design the composition and fabrication process for a low-alloyed Mg-Zn-Ca alloy, showing that it can be extruded at low temperatures (~250 ℃) and high speeds (~2 mm/s). After the extrusion, this alloy exhibits a substantially weakened basal texture, relatively small grain size, very high tensile elongation (~30%), and good strength. The origin of the considerably improved ductility was studied using a combination of three-dimensional atom probe tomography (3D-APT), transmission electron microscopy (TEM), electron backscattered diffraction (EBSD) in conjunction with surface slip trace analysis, in-situ synchrotron X-ray diffraction, and elasto-plastic self-consistent (EPSC) modeling. Co-segregation of Zn and Ca atoms at a grain boundary is observed and associated with texture weakening and grain boundary mediated plasticity, both improving the ductility. While basal slip and prismatic slip are identified as the dominant deformation systems in the alloy, the ratio between their slip resistances is substantially reduced relative to pure Mg and most other Mg alloys, significantly contributing to the improved ductility of the alloy. This Mg-Zn-Ca alloy exhibiting excellent mechanical properties and low fabrication cost is a promising candidate for industrial productions.

Key words: Mg-Zn-Ca alloy, Ductility, Deformation mechanisms, Crystal plasticity modeling, Grain boundary mediated plasticity