In this study, Al-Mg alloys were prepared by vacuum + argon-protected casting. The effects of Sc microalloying on the microstructure and mechanical properties of Al-Mg alloy were studied. The strengthening mechanism of Al-Mg alloy with Sc was discussed. The results show that the average grain size of as-cast Al-Mg alloy with Sc reaches 36.07 μm, which is 74.4% smaller than that of alloy 1 without refiner and 32.0% of alloy 2 with 0.15% Ti. The alloy with Sc has excellent comprehensive mechanical properties, with a tensile strength of 274 MPa and an elongation of 29.67%, and its tensile strength is 10.6% higher than alloy 1 and 7.9% higher than alloy 2. There exist two kinds of fine particles in as-cast Sc-containing Al-Mg alloy, nucleated particles Al₃Sc, and dispersed second-phase particles Al₃(Sc, Ti). The main strengthening mechanisms of the as-cast Al-Mg alloy with Sc reveal the solid solution strengthening of Mg and the fine-grain strengthening effect caused by Sc, accounting for 57.7% and 23.9% to strengthening contribution, respectively.

A weldable Al–Mg–Zn–Sc alloy was produced using vacuum induction melting and an argon-protected casting method to achieve high strength and ductility, and the effects of heat treatment on the microstructure evolution and mechanical properties of Al–Mg–Zn–Sc alloys were comparatively investigated. The results reveal that fine equiaxed grains with an average grain size of 40 μm in an as-cast Al–Mg–Zn–Sc alloy change little after heat treatments, bringing about a grain-boundary strengthening of 46.1 MPa. The coarse T-Mg₃₂(Al, Zn)₄₉ phases at grain boundaries are completely dissolved into the matrix through solid-solution treatment, and T-Mg₃₂(Al, Zn)₄₉ with diameters ranging from 10 to 25 nm and Al₃Sc with diameters ranging from 5 to 20 nm gradually precipitate during the artificial aging process. The Mg solid solubility is 4.67% in the as-cast Al–Mg–Zn–Sc alloy, and it increased to 5.33% after solid-solution treatment and dramatically decreased to 4.15% after post-aging treatment. The contributions of solid-solution strengthening to as-cast, post-solid-solution and post-aging Al–Mg–Zn–Sc alloys are 78.2 MPa, 85.4 MPa and 72.3 MPa, respectively. The precipitation strengthening of the post-aging alloy is 49.7 MPa, which is an increase of 21% in comparison to that of both as-cast and post-solid-solution alloys. The alloy achieves an optimal tensile strength of 355.3 MPa, yield strength of 175 MPa and elongation of 22% after undergoing solid-solution treatment.

Aiming for hydrogen and oxidation easily produced in the melting process of Al-Mg alloys, three processes, including non-vacuum static melt treatment, non-vacuum rotary-injection purification and vacuum-stirring purification, were used to purify the Al-6Mg alloy melt. The hydrogen content and inclusion content were studied by means of the solid-state hydrogen measurement method, reduced pressure test method, FESEM and EDS. The results show that the purification effect of vacuum-stirring purification is better than that of the non-vacuum static melt treatment and non-vacuum rotary-injection purification. The hydrogen content of the melt decreases from 0.48 mL/100 gAl in the non-vacuum static treatment, to 0.32 mL/100 gAl in the non-vacuum rotary-injection purification process and to 0.10 mL/100 gAl in the vacuum-stirring purification process. The inclusion content of the melt decreases from 2.6% in the non-vacuum static treatment to 0.69% in the non-vacuum rotary-injection purification process, and to 0.39%, in the vacuum-stirring purification process.

Al-Mg alloys were fabricated by hot extrusion process after vacuum + argon-protected casting. The effects of Sc microalloying on microstructure and properties of as-extruded Al-5Mg alloy were studied. The results show that alloy 2 containing Sc is partially recrystallized during hot extrusion, resulting in the structure of alloy 2 consisting of 21.8% equiaxed recrystallized structure and 78.2% fine banding structure. The grain size of alloy 2 is about 5.31 μm, which is 83.3% finer than that of alloy 1 without Sc. The sum of the yield strength increments due to grain boundary strengthening (${\sigma }_{GB}$) in alloy 2 is 103.59 MPa, where low angle grain boundary strengthening (${\sigma }_{LAGB})$ is increased by a factor of 4.5, and high angle grain boundary strengthening $\left({\sigma }_{HAGB}\right)$ is increased by 73.4% compared to that of alloy 1. The addition of 0.2% Sc leads to an increase in the lattice strain and dislocation density of alloy 2, and the dislocation strength (${\sigma }_{dis}$) increases to 41.85 MPa. The alloy 2 with Sc has a higher tensile strength of 380.7 MPa, which is 34.1% higher than that of alloy 1, but alloy 2 has a 46.2% reduction in elongation compared to alloy 1.

Novel uniformly passivated nano lithium powder exhibiting high air stability and good electrochemical stability was prepared by an integrated approach combining ultrasonication, in-situ gas-phase passivation in solution, and freeze-drying, and its physicochemical properties were characterized. The passivated powder exhibits a uniform particle size of approximately 0.5 μm and a compact, continuous Li2CO3-rich coating formed on the lithium surface. By using this passivated powder, a lithium powder dry electrode (Lip) with a sandwich architecture (Cu foil/composite powder/Cu mesh) was fabricated by hot rolling. Symmetric cells and lithium-metal batteries composed of a Lip anode and an LFP cathode were assembled and evaluated. The resulting Lip||Lip symmetric cell sustains stable cycling for 1320 h, far exceeding the 384 h of the Li sheet counterpart, while the Lip electrode in LFP full cells delivers a high capacity retention of 95% after 800 cycles at 1C with a stable Coulombic efficiency of 99.9%, compared with 80% and 86% for the Li sheet electrode. The morphological and impedance analyses of the Lip reveal that the dendrite growth and SEI degradation during cycling can be effectively suppressed by using the synergistic 3D conductive scaffold (CNTs conductive additive and Cu mesh) and PEO network.