This study investigates the ductile fracture behavior of Mg-Zn-Ca alloy microtubes during extrusion. Uniaxial tension, shear, and compression tests were conducted at 250–450 °C to characterize the plastic and fracture properties under various stress states. The failure strain increased with temperature under all tested stress states, with the largest increase occurring between 250 and 350 °C. This temperature dependence was more pronounced under shear loading than under uniaxial tension or compression. To capture the coupled effects of temperature and stress triaxiality on fracture, a damage model was developed using the GISSMO-SAMP framework with a Hosford-Coulomb-based fracture locus. The model was validated by comparing the predicted fracture locations and extrusion outcomes with extrusion experiments conducted at 350–400 °C. The simulations showed that microtube extrusion promotes a local transition of the stress state from compression toward shear near the die entry, which accelerates damage accumulation and leads to ductile fracture. To identify conditions that prevent this failure, processing temperatures and microtube dimensions were systematically varied. Within the investigated process window, the safe zone indicates that processing temperature has a stronger influence on formability than microtube dimensions under high extrusion-ratio conditions.
The kinetic analysis of metal hydride systems under operando conditions is essential for evaluating their performance and stability in a hydrogen-based energy system. In this work, we use operando optical microscopy in combination with theoretical solid-state reaction kinetic models to unravel hydrogen sorption kinetics in a straightforward, accessible, and cost-effective manner. Optical microscopy methods can directly monitor reaction progress by leveraging the pronounced optical contrast arising from the phase transitions exhibited by many metal hydrides. The archetypal system of Mg thin films of 100 nm capped with Pd is employed to validate the correlation between the intensity of transmitted light during hydrogenation and solid-state kinetic models, thereby revealing the rate-limiting steps of the process. Comparison of the obtained results with structural measurements confirms the accuracy of this methodology, allowing reliable determination of activation energies and the time evolution of the rate-limiting mechanism. This work highlights operando optical microscopy as a readily available technique for determining H-sorption mechanisms, offering a straightforward alternative to conventional, indirect, or complex methods while maintaining accuracy and accessibility.
AZ91D magnesium alloy and 2 wt.% TiB₂/AZ91D composite were fabricated by laser powder bed fusion (LPBF) to improve the stiffness of AZ-series magnesium alloys. The effects of LPBF processing parameters, TiB₂ addition and T4 heat treatment on defect characteristics, microstructure, Young’s modulus and tensile response were investigated. Under the best-performing LPBF condition within the investigated parameter range, the AZ91D alloy exhibited limited visible defects, fine equiaxed grains with an average size of approximately 3–4 µm, and discrete β-Mg₁₇Al₁₂ particles in the Mg matrix. The alloy fabricated under this condition achieved a yield strength of 219.1 ± 13.5 MPa, an ultimate tensile strength of 329.5 ± 0.4 MPa, and an elongation of 7.3 ± 1.4%. TiB₂ addition increased the Young’s modulus from 44.2 ± 1.2 GPa for AZ91D to 56.4 ± 1.0 GPa for the as-printed TiB₂/AZ91D composite, corresponding to an increase of approximately 28%. However, the as-printed composite showed reduced ultimate tensile strength and elongation compared with the AZ91D alloy fabricated under the best-performing condition, which can be associated with residual pores and local TiB₂-rich regions. After T4 treatment at 420 °C for 6 h followed by water quenching, the representative composite retained a high Young’s modulus of 56.2 ± 1.3 GPa. Although the yield strength decreased to 187.3 ± 2.1 MPa, the ultimate tensile strength and elongation increased to 317.3 ± 3.8 MPa and 6.7 ± 1.3%, respectively. The improved tensile deformation capability is likely related to the partial dissolution of β-Mg₁₇Al₁₂ during solution treatment. These results indicate that TiB₂ reinforcement combined with T4 treatment is an effective strategy for improving the stiffness of LPBF-fabricated AZ91D alloy while maintaining acceptable tensile ductility.
Aqueous magnesium-ion batteries (AMIBs) have attracted considerable attention as promising next-generation energy-storage systems because of their low cost, high safety, environmental compatibility, and high ionic conductivity. As conventional lithium-ion batteries face growing concerns regarding resource availability, material cost, and safety, Mg has emerged as an attractive alternative owing to its high theoretical capacity, natural abundance, and economic potential. However, the reversible use of Mg metal is hindered by severe interfacial passivation, which led early rechargeable Mg battery research to focus largely on non-aqueous electrolytes. Their high viscosity, low ionic conductivity, complex handling, high cost, and flammability have subsequently motivated the development of aqueous systems. Nevertheless, AMIBs remain limited by the narrow electrochemical stability window of water, sluggish Mg2+ desolvation and solid-state diffusion, structural instability of electrode materials, Mg metal passivation, and parasitic hydrogen evolution. This review summarizes recent progress in electrolyte design, insertion-type cathode and anode materials, Mg metal interfacial stabilization, and full-cell configurations, while highlighting the key challenges and future directions for high-performance AMIBs. These developments are connected here to a single underlying variable, namely the strong electrostatic interaction between the divalent Mg2+ ion and its surrounding anionic environment, which most successful electrode and electrolyte designs act to screen.
Reliable constitutive parameters are essential for microstructure-based mechanical modeling of Mg-RE alloys containing long-period stacking ordered (LPSO) phases. However, owing to the in-situ formation and limited size of the LPSO phase, together with the solid-solution nature of the magnesium matrix, their independent constitutive parameters cannot be directly obtained using conventional mechanical testing. To address this challenge, this study decouples the elastic-plastic constitutive parameters of the magnesium matrix and LPSO phase within a Mg-Gd-Y-Zn-Zr alloy by means of the targeted nanoindentation experiment. The load-displacement curves for the magnesium matrix and LPSO phase were obtained from the nanoindentation experiments, which were used to determine their Young’s modulus (E), yield strength (σ y ) strength coefficient (K), and strain-hardening exponent (n), combining the numerical analysis method. Results shows that the magnesium matrix possesses Young’s modulus of 45.7 GPa, yield strength of 335.0 MPa, strength coefficient of 439.1 MPa and strain-hardening exponent of 0.055, while the LPSO phase shows substantially higher corresponding values of 56.7 GPa, 536.5 MPa, 854.7 MPa and 0.100, respectively. In order to verify the accuracy of these parameters, the finite element models were used to simulate the nanoindentation experiment for the magnesium matrix and the LPSO phase. With these parameters, the load-displacement curves and residual indentation morphologies in the simulated models show excellent agreement with that in the experimental results for both the magnesium matrix and the LPSO phase, validating the accuracy of these constitutive parameters. The decoupled parameters provide a reliable independent stress-strain relationship for the magnesium matrix and the LPSO phase, serving as the critical data for multiphase microstructural modeling of the Mg-Gd-Y-Zn-Zr alloy.
