J. Mater. Sci. Technol. ›› 2022, Vol. 99: 223-238.DOI: 10.1016/j.jmst.2021.04.074

• Research article • Previous Articles     Next Articles

Combining gradient structure and supersaturated solid solution to achieve superior mechanical properties in WE43 magnesium alloy

Wanting Suna, Bo Wua, Hui Fua, Xu-Sheng Yanga,b,*(), Xiaoguang Qiaod, Mingyi Zhengd,*(), Yang Hee, Jian Luf, San-Qiang Shic,*()   

  1. aState Key Laboratory of Ultra-precision Machining Technology, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
    bHong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, China
    cDepartment of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
    dSchool of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
    eCentre for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, China
    fDepartment of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong, China

Abstract:

In this study, surface mechanical attrition treatment was employed to sucessfully produce a gradient nanostructured layer on WE43 magnesium alloy. X-ray diffraction, energy dispersive X-ray spectrometer, and high-resolution transmission electron microscope observations were mainly performed to uncover the microstructure evolution responsible for the refinement mechanisms. It reveals that the grain refinement process consists of three transition stages along the depth direction from the core matrix to the topmost surface layer, i.e., dislocation cells and pile-ups, ultrafine subgrains, and randomly orientated nanograins with the grain size of ~40 nm. Noticeably, the original Mg3RE second phase is also experienced refinement and then re-dissolved into the α-Mg matrix phase, forming a supersaturated solid solution nanostructured α-Mg phase in the gradient refined layer. Due to the cooperative effects of grain refinement hardening, dislocation hardening, and supersaturated solid-solution hardening, the gradient nanostructured WE43 alloy contributes to the ultimate tensile strength of ~435 MPa and ductility of ~11.0%, showing an extraordinary strain hardening and mechanical properties among the reported severe plastic deformation-processed Mg alloys. This work provides a new strategy for the optimization of mechanical properties of Mg alloys via combining the gradient structure and supersaturated solid solution.

Key words: Mg-RE alloy, Surface mechanical attrition treatment, Gradient nanostructure, Supersaturated solid solution, High strength and ductility, Strengthening mechanisms