Magnesium alloys act as potential candidate nuclear materials due to their excellent chemical compatibility and neutron economy. In this work, the irradiation behavior of pure Mg, Mg-3Mn and Mg-3Mn-0.5Ca alloys were studied via Xe⁺ implantation at room temperature. Transmission electron microscopy (TEM) results show the formation of dislocation loops, Xe bubbles and Mn nanoprecipitates in irradiated Mg samples. For Mg-3Mn alloy, the high density of Mn nanoprecipitates are formed periodically along the basal plane after Xe irradiation. It is noted that these nanoprecipitates could suppress the nucleation and growth of Xe bubbles to reduce the swelling ratio (only, 0.011 %), which is much less than that of pure Mg. In contrast, the pre-existing Mn particles in the Mg-3Mn-0.5Ca alloy will cause the absence of Mn nanoprecipitates under Xe irradiation. In addition, the irradiation-induced Mn nanoprecipitates could restrict the growth of c-loops and facilitate more c-loops nucleation. Eventually, under the irradiation dose of 9.7 dpa, a high-density c-loop dislocation is formed, with no detectable a-loop formation in the Mg-3Mn sample. The present study could provide a reference for designing the irradiation resistance Mg alloys.

Low absolute strength becomes one major obstacle for the wider applications of low/no rare-earth (RE) containing Mg alloys. This review firstly demonstrates the importance of grain refinement in improving strength of Mg alloys by comprehensively comparing with other strategy, e.g., precipitation strengthening. Dynamic recrystallization (DRX) plays a crucial role in refining grain size of Mg wrought alloys. Therefore, secondly, the DRX models, grain nucleation mechanisms and the related grain refinement abilities in Mg alloys are summarized, including phase boundary, twin boundary and general boundary induced recrystallization. Thirdly, the newly developed low-RE containing Mg alloy, e.g., Mg-Ce, Mg-Nd and Mg-Sm based alloys, and the RE-free Mg alloys, e.g., Mg-Al, Mg-Zn, Mg-Sn and Mg-Ca based alloy, are reviewed, with the focus on enhancing the mechanical properties mainly via the grain refinement strategy. At the last section, the perspectives and outstanding issues concerning high-performance Mg wrought alloys are also proposed. This review is meant to promote the deep understanding on the critical role of grain refinement in Mg alloys and provide reference for the development of other high strength and low-cost Mg alloys which are fabricated by the conventional extrusion/rolling processing.

In this work, a new strategy for achieving ultrahigh strength in the coarse-grained Mg-Gd binary alloy via utilizing recrystallization texture hardening and maximizing precipitation strengthening has been reported. Forging at a much high temperature suppresses dynamic precipitation, enabling the super-saturation of Gd atoms in Mg matrix. This facilitates the formation of fully recrystallized grains with strong texture and induces an exceptionally high precipitation hardening in the following ageing. Therefore, the forged Mg-13Gd sample exhibited extraordinary tensile yield strength (TYS) of ~430 MPa, in which ageing-induced TYS increment exceeds ~210 MPa, as the highest record so far in precipitation-hardened Mg communities. These results provide important theoretical guidance for fabricating the large section and high-strength Mg components for industrial applications.