Microstructure and mechanical properties of extruded Mg–Gd–Y–Zn alloy with Mn or Zr addition

Abstract

The microstructure and mechanical properties of the extruded Mg–2Gd–1.2Y–0.5Zn (at.%) alloy with Mn or Zr addition were investigated. The results show that Zr addition refines the microstructure of the homogenized alloy more efficiently and facilitates the dissolution of the secondary phases in comparison with Mn addition. After extrusion at 400 °C, both Mn and Zr added alloys exhibit bimodal microstructure comprising fine dynamically recrystallized (DRXed) grains with random orientations as well as coarse unDRXed grains with strong $$ \left\langle {10\bar{1}0} \right\rangle $$ //ED fiber texture. Thin long period stacking ordered phases and γ precipitates distribute in the unDRXed grains and nano-sized β phases mainly pin at the DRXed grain boundaries. While the coarse initial grain size of homogenized Mn added alloy leads to its lower DRX ratio and stronger texture intensity after extrusion with respect to Zr added alloy. High strength, moderate ductility and improved yield anisotropy are obtained in both extruded alloys. The Mn added alloy exhibits higher strength with ultimate tensile strength of 437 MPa, 0.2% tensile proof stress of 381 MPa but lower elongation to failure of 4.7% than Zr added alloy, which is mainly due to the lower DRX ratio of Mn added alloy.