Jia She

The low thermal conductivity of magnesium-based metal hydride (MH) beds limits the dehydrogenation performance of hydrogen storage tanks, making effective thermal management essential. In this study, a three-dimensional multiphysics model of a magnesium-based hydrogen storage tank equipped with a U-tube and H-shaped fin heat exchanger was developed using COMSOL Multiphysics. The model couples heat transfer, hydrogen transport, and dehydrogenation kinetics, with the heat transfer fluid (HTF) represented by a convective boundary condition based on a turbulent correlation to investigate the effects of the initial MH bed temperature and HTF temperature on dehydrogenation behavior. The results show that the proposed heat exchanger provides continuous heat transfer pathways and improves temperature uniformity of the MH bed. Dehydrogenation initiates near the hydrogen outlet and gradually propagates throughout the tank. A higher initial MH bed temperature significantly accelerates the early-stage reaction, while a higher HTF temperature provides sustained heat input and shortens the time required to achieve high hydrogen conversion. These findings improve the understanding of coupled heat and mass transfer during dehydrogenation and provide theoretical guidance for the thermal management and design optimization of magnesium-based hydrogen storage tanks.

Addressing the challenge of synergistically optimizing shielding performance and mechanical properties in nuclear radiation shielding materials, this study designed and prepared as-cast Mg-12Dy-xSm-0.4Zr (x = 1, 2, 3) alloys by incorporating rare earth elements Dy and Sm, which possess high thermal neutron absorption cross-sections. The co-addition of Sm and Dy significantly refined the grains and promoted the precipitation of bone-like Mg₅(Sm,Dy) and Mg₄₁Sm₅ phases along grain boundaries. The alloys exhibited favorable mechanical properties, with ultimate tensile strength (UTS) reaching up to 194.6 MPa and elongation (EL) up to 10.9%. However, higher Sm content led to an increased amount of secondary phases at grain boundaries, resulting in stress concentration and a subsequent decline in both yield strength and elongation. Moreover, the combined addition of Dy and Sm markedly enhanced the thermal neutron shielding performance. Experimental results agreed well with Geant4 simulations, showing that both the neutron shielding rate and linear attenuation coefficient improved with increasing Sm content, demonstrating the positive role of Dy and Sm in neutron absorption. The developed alloy achieves simultaneous improvement in mechanical properties and neutron shielding capacity, providing valuable insights for the development of lightweight “function–structure integrated” radiation shielding materials for applications such as nuclear medicine and aerospace.

The development of low-cost and high-performance Mg alloys is an important way to achieve further application of magnesium alloys. In this work, the as-extruded Mg_98.3−xZn_xGd₁Sm_0.7 alloy with excellent mechanical properties is successfully prepared by regulating the bimodal-grained structure. The effect of the Zn content on the microstructure evolution and mechanical properties of the as-extruded Mg_98.3−xZn_xGd₁Sm_0.7 alloy is systematically investigated. The results show that the addition of Zn increases the dynamic recrystallization (DRX) fraction and weakens the basal texture of the as-extruded alloy. The Mg_98.05Zn_0.25Gd₁Sm_0.7 alloy exhibits a typical bimodal-grained structure. A large amount of geometrically necessary dislocations (GNDs) are generated at the interface between the soft zone and the hard zone of the bimodal-grained structure during the plastic deformation process, resulting in back stress strengthening, thereby improving the strength of the alloy. And it achieves exceptional mechanical properties with an ultimate tensile strength (UTS) of 330 MPa, a yield strength (YS) of 248 MPa, and an elongation (EL) of 18.5% at room temperature. This paper provides a new idea for introducing a heterogeneous structure and improving the strength of low-cost Mg alloys.

The double-aging strengthening effect of the γ’ phase in 945A nickel-based alloy was investigated. The double-aging treatment significantly improved the compressive yield stress. The sample after 8 h aging at 725 °C and 96 h at 800 °C exhibited the highest compressive yield stress of 1007 MPa, which greatly exceeded the original state of 229 MPa. The strengthening mechanism is mainly attributed to the Orowan strengthening mechanism. After double-aging treatment, high density γ’ phase precipitate was formed, which effectively improves the strength. The precipitate behavior and the strengthening mechanism of γ’ phase precipitates were clarified in detail.

Hot rolling was carried out in this study to modify the microstructures of an extruded Mg–6Al–1Sn–0.3Mn alloy sheet and investigate its effects on mechanical properties. After hot rolling, the grains and second phase of the extruded alloy sheet were remarkably refined, and the c-axis of a few grains was parallel to the transverse direction. The strength improvement was mainly attributed to the grain and Mg₁₇Al₁₂ particle refinement due to the Hall–Petch effect and the Orowan mechanism. The random orientation of the fine grains resulted in improving ductility and anisotropy.