Mg-based Alloys Research Articles

Surface microstructure and corrosion resistance characterization of Mg-based amorphous alloys

Surface microstructure and corrosion resistance characterization of Mg-based amorphous alloys

Measurement of phase equilibria in Mg-Ag-Er ternary system

The isothermal sections of the Mg-Ag-Er ternary system at 400 °C and 500 °C have been experimentally determined by using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and X-ray diffraction (XRD). 19 and 13 three-phase regions were established at 400 and 500 °C, respectively. 3 new ternary compounds, τ1, τ2, and τ3, were detected at 400 °C, all of which transformed to liquid phase at 500 °C. Especially, the phase τ1 was found to be of a face-centred cubic structure belonging to the space groupFd3¯m, with a lattice parameter of a = 16.053 Å. In addition, τ1 melts at about 439.1 °C and the composition range of τ1 is Mg81.89–84.38Ag9.20–11.33Er5.39–7.69. The present study can provide substantial experiments for thermodynamic optimization of the Mg-Ag-Er system, and helpful for Mg-based alloy design.

Enhanced Cycling Stability of Amorphous MgNi-Based Alloy Electrodes through Corrosion Prevention by Incorporating Al2(SO4)3·18H2O into the Electrolyte

Mg-based alloy anodes suffer from severe corrosion in alkaline electrolytes, which substantially impedes their cycle life and thereby limits their suitability as anode materials for nickel–metal hydride (Ni-MH) batteries. This work modifies the conventional 6 M KOH electrolyte by adding 0.1 M Al2(SO4)3·18H2O. The electrochemical hydrogen storage properties of Mg0.45Ti0.05Ni0.50 alloy in this electrolyte and its microstructural evolution during cycling are studied. In the 6 M KOH + 0.1 M Al2(SO4)3·18H2O electrolyte, a protective layer consisting of Mg2Al(OH)7 is formed on the surface of the Mg0.45Ti0.05Ni0.50 alloy anode during charge/discharge cycling instead of Mg(OH)2, effectively preventing further corrosion and improving its cycle life. The Mg0.45Ti0.05Ni0.50 alloy anode delivers a maximum discharge capacity of 479.0 mAh g−1 and maintains 318.4 mAh g−1 after 30 cycles in the 6 M KOH + 0.1 M Al2(SO4)3·18H2O electrolyte, which is significantly superior to that achieved in the 6 M KOH electrolyte (471.1 mAh g−1 and 201.8 mAh g−1, respectively). This work provides a new strategy for improving the cycle stability of Mg-based alloy anodes.

Harnessing machine learning for predicting mechanical properties of lightweight Mg alloys

In this study, we introduce a machine learning methodology for predicting mechanical properties in Mg-based multicomponent alloys, incorporating alloying elements and processing methods as input variables. We employed eight ML models and assessed their efficacy using metrics such as R2, RMSE, and MAE after using five-fold cross validation grid search hyperparameters tuning process. Following this, we implemented the top-performing Extra Tree (ET), Random Forest (RF) and XGB models to predict mechanical properties for Mg alloys. The best performance was observed with an R2 of 95.1 % and 97.2 %, RMSE of 7 % and 8 %, and MAE of 4.7 % and 5 % for UTS and YS respectively using the Extra Tree model. This research not only showcases the efficiency of ML techniques with minimal intervention but also offers valuable insights paving the way for accelerated design of Mg-alloys for tailored application in the future.

Design of air-stabilized Mg-Sc alloy with enhanced hydrogen storage properties via in-situ formation of Sc-hydride in Sc dissolved phase

Severe surface oxidation and slow kinetic rates are the main obstacles which limit the industrial application of Mg-based hydrogen storage alloys. In this work, an attempt is carried out to design and develop the highly active and air-stabilized Mg-Scx (x = 1, 2 and 3 at.%) alloys via an inexpensive and efficient method. The Sc atoms are completely dissolved in the Mg matrix to form single-phase solid solution alloy. At 325 °C and 2.0 MPa hydrogen pressure, Mg-Sc2 alloy exhibits the rapidest absorption rate with the hydrogen capacity of 6.25 wt%. The synergism of lattice distortion induced by Sc-doping and the in-situ formed ScH2 nanoparticles enhance the de/hydrogenation kinetics. After exposed to air for 800 h, almost no MgO can be detected and the hydrogen storage capacity is only reduced by 0.11 wt%, maintaining the initial total capacity more than 98 %. Sc can protect Mg-based alloys from O2 and H2O pollution, which is ascribed to the formation of an oxygen atoms exclusion zone around the solute atoms caused by valence electrons transfer.

SrHPO4-coated Mg alloy implant attenuates postoperative pain by suppressing osteoclast-induced sensory innervation in osteoporotic fractures

Osteoporotic fractures have become a common public health problem and are usually accompanied by chronic pain. Mg and Mg-based alloys are considered the next-generation orthopedic implants for their excellent osteogenic inductivity, biocompatibility, and biodegradability. However, Mg-based alloy can initiate aberrant activation of osteoclasts and modulate sensory innervation into bone callus resulting in postoperative pain at the sequential stage of osteoporotic fracture healing. Its mechanism is going to be investigated. Strontium hydrogen phosphate (SrHPO4) coating to delay the Mg-based alloy degradation, can reduce the osteoclast formation and inhibit the growth of sensory nerves into bone callus, dorsal root ganglion hyperexcitability, and pain hypersensitivity at the early stage. Liquid chromatography-mass spectrometry (LC-MS) metabolomics analysis of bone marrow-derived macrophages (BMMs) treated with SrHPO4-coated Mg alloy extracts shows the potential effect of increased metabolite levels of AICAR (an activator of the AMPK pathway). We demonstrate a possible modulated secretion of AICAR and osteoclast differentiation from BMMs, which inhibits sensory innervation and postoperative pain through the AMPK/mTORc1/S6K pathway. Importantly, supplementing with AICAR in Mg-activated osteoclasts attenuates postoperative pain. These results suggest that Mg-induced postoperative pain is related to the osteoclastogenesis and sensory innervation at the early stage in the osteoporotic fractures and the SrHPO4 coating on Mg-based alloys can reduce the pain by upregulating AICAR secretion from BMMs or preosteoclasts.

Accelerated discovery of Magnesium-based amorphous alloys through a property-driven active learning strategy

Magnesium (Mg)-based amorphous alloys hold significant potential for applications in the automotive, aerospace, and biomedical industries. However, they are limited by their smaller size compared to other amorphous alloys. A higher reduced glass transition temperature (Trg) is associated with larger sizes in Mg-based amorphous alloys. Yet, due to the vast chemical space involved, designing Mg-based amorphous alloys with higher Trg using traditional ‘trial and error’ method is a challenging endeavor. In this work, we developed a property-driven active learning strategy to customize Mg-based amorphous alloys with enhanced Trg. After just two iterations, we successfully tailored four amorphous alloys with high Trg values. Under identical experimental conditions, two of these alloys exhibited Trg values surpassing that of Mg0·65Ag0·19Cu0.06Gd0.1, the alloy with best Trg value in the reported references. SHAP analysis revealed that Trg tends to be higher when the Ag atomic ratio exceeds 0.045, the Cu atomic ratio is below 0.18, the Ni atomic ratio is below 0.025, and the Mg atomic ratio is below 0.665. Our work offers a reliable strategy for designing Mg-based amorphous alloys with higher Trg and provides valuable insights for the rational design of these alloys.

Mg alloy scaffold with spherical/cubic hybrid pores for orthopedic repair

Biodegradable Mg-based scaffolds are regarded as potential bone tissue engineering materials for a promising approach to bone repair. In this work, the spherical/cubic hybrid pore-forming agents were introduced to prepare a porous Mg-based alloy scaffold by the negative salt pattern molding method. The porous Mg-Zn-Ca alloy scaffold containing spherical/cubic hybrid pores exhibited a porosity of about 68.60 % and a surface area ratio of about 7.88 cm2/cm3. The compressive elastic modulus was about 0.32 GPa and the compressive strength was about 4.22 MPa, close to cancellous bone. However, the rapid degradation of Mg alloy scaffold was inadaptive to orthopedic repair. Thus, a calcium phytate coating was prepared on the Mg-based scaffold for surface modification to retard rapid corrosion.

Ternary Mg-Sc-based TRIP alloys: Design strategy based on Sc-equivalent

This study addresses the transformation-induced plasticity (TRIP) effect observed in bcc single-phase Mg–Sc alloys, aiming to circumvent the strength-ductility tradeoff inherent in traditional Mg-based alloys. Introducing a third element (X = Zn, Y, Nd, Gd) significantly enhanced the strength of the binary Mg–Sc TRIP alloys, simultaneously preserving ductility due to the TRIP effect. Consequently, a ternary Mg–Sc–X TRIP alloy with a bcc single-phase, for instance, achieved an ultimate tensile strength of approximately 380 MPa and a fracture elongation of around 41%, surpassing the conventional tradeoff. Furthermore, we introduce the design strategy of Sc-equivalent (Sceq) to articulate the combined influence of Sc and X elements on the stability of the bcc phase. This novel approach demonstrates the room-temperature deformation behavior of the Mg–Sc–X ternary alloy can be predicted and modulated, showcasing superelasticity (17.5 < Sceq < 19.5) and TRIP effect (19.0 < Sceq < 21.0).

Effect of Mn, Ni, and Zr Addition on the Tensile Properties and Precipitation Behavior of Sr-Modified Al–Si–Cu–Mg-Based Alloys

Effect of Mn, Ni, and Zr Addition on the Tensile Properties and Precipitation Behavior of Sr-Modified Al–Si–Cu–Mg-Based Alloys

Mg-based alloys with Y, Ca and Al reaching exceptional ignition resistance and suppressed flammability

Magnesium alloys are increasingly pivotal in automotive and aerospace engineering due to their superior strength-to-weight ratio. This rising prominence necessitates advancements in their mechanical characteristics, such as tensile strength, ductility, and fatigue endurance, alongside enhanced control over their interaction with oxygen. A critical phenomenon in this context is the ignition of magnesium in oxygen-rich environments at high temperatures. This exothermic reaction induces a rapid temperature surge, potentially reaching 3000 °C, leading to the catastrophic disintegration of magnesium alloy components. Consequently, research in magnesium technology also focuses on augmenting the ignition threshold and diminishing the material's combustibility. This expansion in the application scope for magnesium alloys in the aviation and aerospace sectors hinges on developing novel alloy compositions. Elements like yttrium (Y), rare-earth elements, and calcium (Ca) are under exploration for their potential to bolster ignition resistance in magnesium alloys. However, the impact of these elements on ignition and flammability is highly dependent on their concentration and the overall alloy chemistry. Four magnesium alloys, integrating yttrium, calcium, and aluminium – a conventional element in commercial alloys – were synthesised in the study under discussion through casting and thermal processing. These alloys were methodically examined for microstructural evolution and their resistance to ignition and flammability. The results demonstrated that when appropriately balanced with yttrium, aluminium is a viable alloying element in magnesium alloys without significantly compromising ignition resistance. The alloy WAX211 exhibited the highest ignition temperature of 940 °C, attributed to the synergistic effects of calcium and yttrium and the formation of a highly stable protective oxide layer.

Electrical conductivity of binary magnesium alloys: Integrating first-principles and machine learning studies

The electrical conductivity is the fundamental physical property of Mg alloys and the basic information for the design of comprehensive high-performance Mg alloys. In this work, the electrical conductivity of 29 Mg-based binary alloys has been calculated using the first-principles methods and the main factors have been analyzed by machine learning. It is found that the electrical conductivity values of the binary alloys containing elements located in the s region and p region of the periodic table are bigger than others of alloys contain alloying elements in the f region and d region. The results of machine learning show that the difference ratio of volume (∆V/VMg), extra-nuclear electron configuration and difference of valence () play the main controlling role, followed by solid solubility and electronegativity of the alloying element. For solid solution elements in Mg-based binary alloys, the impact weight on the electrical conductivity is: difference ratio of volume > number of extra-nuclear electron vacancy > difference of valence.

Crack elimination and strength enhancement mechanisms of selective laser melted Si-modified Al−Mn−Mg−Er−Zr alloy

In order to increase the processability and process window of the selective laser melting (SLM)-fabricated Al−Mn−Mg−Er−Zr alloy, a novel Si-modified Al−Mn−Mg−Er−Zr alloy was designed. The effect of Si alloying on the surface quality, processability, microstructure, and mechanical properties of the SLM-fabricated alloy was studied. The results showed that introducing Si into the Al−Mn−Mg−Er−Zr alloy prevented balling and keyhole formation, refined the grain size, and reduced the solidification temperature, which eliminated cracks and increased the processability and process window of the alloy. The maximum relative density of the SLM-fabricated Si/Al−Mn−Mg−Er−Zr alloy reached 99.6%. The yield strength and ultimate tensile strength of the alloy were (371±7) MPa and (518±6) MPa, respectively. These values were higher than those of the SLM-fabricated Al−Mn−Mg−Er−Zr and other Sc-free Al−Mg-based alloys.

Machine learning insights into prediction of H2 gravimetric capacity in Mg-based pure metal alloys

Hydrogen is emerging as a crucial clean energy carrier, but storage challenges remain. Magnesium has the highest hydrogen storage capacity among metals, yet its high thermodynamic stability, desorption temperature, and slow reaction rates hinder practical use. Identifying suitable metal alloys for magnesium remains challenging. This study employs ML-framework with 13 inputs to predict H2 storage and release capacity (2 outputs) in Mg-based alloys, with database comprises 792 storage and 279 release observations. Linear-models initially performed poorly, leading to the development of nonlinear models such as tree ensembles, kernel based methods, and neural networks. After hyperparameter tuning with 5-fold cross-validation, an ANN with Bayesian regularization achieved higher accuracy in predicting hydrogen gravimetric capacity (R2 = 0.86 for storage, R2 = 0.93 for release for test data). With this model, post-analysis revels key-factors influencing hydrogen uptake are particle size, Mg composition, and pressure, while temperature and time significantly affect hydrogen release. Finally, this study identifies operating ranges for these factors, providing insights for improving/accelerating Mg based hydrogen storage materials development.

MgCa-Based Alloys Modified with Zn- and Ga-Doped CaP Coatings Lead to Controlled Degradation and Enhanced Bone Formation in a Sheep Cranium Defect Model.

Mg-based biodegradable metallic implants are gaining increased attraction for applications in orthopedics and dentistry. However, their current applications are hampered by their high rate of corrosion, degradation, and rapid release of ions and gas bubbles into the physiological medium. The aim of the present study is to investigate the osteogenic and angiogenic potential of coated Mg-based implants in a sheep cranial defect model. Although their osteogenic potential was studied to some extent, their potential to regenerate vascularized bone formation was not studied in detail. We have studied the potential of magnesium-calcium (MgCa)-based alloys modified with zinc (Zn)- or gallium (Ga)-doped calcium phosphate (CaP) coatings as a strategy to control their degradation rate while enhancing bone regeneration capacity. MgCa and its implants with CaP coatings (MgCa/CaP) as undoped or as doped with Zn or Ga (MgCa/CaP + Zn and MgCa/CaP + Ga, respectively) were implanted in bone defects created in the sheep cranium. MgCa implants degraded faster than the others at 4 weeks postop and the weight loss was ca. 50%, while it was ca. 15% for MgCa/CaP and <10% in the presence of Zn and Ga with CaP coating. Scanning electron microscopy (SEM) analysis of the implant surfaces also revealed that the MgCa implants had the largest degree of structural breakdown of all the groups. Radiological evaluation revealed that surface modification with CaP to the MgCa implants induced better bone regeneration within the defects as well as the enhancement of bone-implant surface integration. Bone volume (%) within the defect was ca. 25% in the case of MgCa/CaP + Ga, while it was around 15% for undoped MgCa group upon micro-CT evaluation. This >1.5-fold increase in bone regeneration for MgCa/CaP + Ga implant was also observed in the histopathological examination of the H&E- and Masson's trichrome-stained sections. Immunohistochemical analysis of the bone regeneration (antiosteopontin) and neovascularization (anti-CD31) at the defect sites revealed >2-fold increase in the expression of the markers in both Ga- and Zn-doped, CaP-coated implants. Zn-doped implants further presented low inflammatory reaction, notable bone regeneration, and neovascularization among all the implant groups. These findings indicated that Ga- and Zn-doped CaP coating is an important strategy to control the degradation rate as well as to achieve enhanced bone regeneration capacity of the implants made of Mg-based alloys.

Effects of homogenization temperature on microstructure, mechanical properties and corrosion behavior of binary Zn-Mn alloys extruded at different temperatures

In order to optimize the mechanical properties (MPs) of biodegradable Zn-based alloys, many researches have been conducted. However, the effect of homogenization treatment before the plastic deformation process on the MPs of biodegradable Zn-based alloys has not received sufficient attention, although it has been demonstrated to play an important role in improving the MPs of Al- and Mg-based alloys. In this work, as-cast Zn-0.8 wt% Mn alloys were firstly homogenized at two different temperatures (330 and 390 °C) followed by quenching and then extruded at three different temperatures (170, 230 and 300 °C). This work revealed the effects of homogenization temperature (HT) on microstructure, MPs and corrosion behavior of Zn-0.8 wt% Mn alloys extruded at different temperatures. The results showed that compared to the alloy homogenized at 330 °C (HT330), the alloy homogenized at 390 °C (HT390) has less precipitation of micron-sized MnZn13 particles in the homogenization process. During the subsequent extrusion processes at 170 and 230 °C, more submicron-sized MnZn13 particles are precipitated and finer Zn grains are formed in the HT390 alloys than in the HT330 alloys. Correspondingly, the two extruded HT390 alloys exhibit elongations of up to 133 % and 86 %, respectively, which are much higher than the 71 % and 65 % of the two extruded HT330 alloys. However, when the extruding temperature is elevated to 300 °C, high HT causes decrease in the fraction of both the micron- and submicron-sized MnZn13 particles as well as coarsening of Zn grains, followed by an increase in the strength of the as-extruded alloy. In addition, high HT is conductive to improving the corrosion resistance of the as-extruded alloys regardless of the extrusion temperature.

Enhancement mechanism of low alloying (Mn, Al) and plastic deformation for hydrogen storage kinetics of Mg alloy

The sluggish kinetics are a momentous hurdle for the application of Mg-based hydrogen storage alloys. To improve the kinetics, Mg-xMn-0.5Al alloys (x = 0, 0.5, 1, 2) were fabricated by combining low alloying strategy and plastic deformation. The results demonstrate that both low alloying and plastic deformation enhance the kinetic properties of hydrogen adsorption and desorption. The resulting Mg-2Mn-0.5Al alloy after plastic deformation can absorb ca. 5 wt% hydrogen within 3 min at 623 K, and the dehydrogenation activation energy (ca. 125 kJ/mol) is substantially reduced versus Mg (ca. 166 kJ/mol). The co-addition of Mn and Al can introduce more second phases, and the pinning effect of Al8Mn5 and α-Mn on grain boundaries can promote grain refinement and dislocation proliferation. The increase of grain boundaries, phase interfaces and dislocations accelerates the H atoms diffusion, benefitting the hydrogen absorption. Plastic deformation generates plenty of nanoscaled Al8Mn5 particles, which can serve as additional heterogeneous nucleation sites of Mg during dehydrogenation. Low alloying of Mn and Al combined with plastic deformation is a low-cost and effective way to improve the hydrogen storage kinetics of Mg-based alloys.

Ternary Mg alloy-based artificial interphase enables high-performance rechargeable magnesium batteries

Rechargeable magnesium batteries (RMBs) provide potential advantages over lithium-ion batteries in terms of high volumetric capacity, natural abundance, and high safety. However, the rational design of high-performance magnesium-based metal anodes compatible with conventional electrolytes is a big challenge for the viability of RMBs. In this work, an in-situ formed ternary alloy-based artificial interphase layer on Mg foil as an anode was successfully prepared through a facile and universal electrodeposition strategy. The Mg-Sn-Bi@Mg anode provides high charge transfer dynamics for Mg deposition and constructs a reduced energy barrier for Mg2+ ions desolvation. Thanks to the unique Mg deposition behaviors, the Mg-Sn-Bi@Mg alloy anode demonstrates a low overpotential of 39.4 mV and a long cycle life of >2000 h. The transfer kinetics for RMBs can be largely improved due to the unique alloying reactions. Density functional theory (DFT) calculations demonstrate that the designed ternary alloy-based artificial interphase layer enables faster Mg2+ ion migration than the bare Mg electrode. Full cells with Mo6S8 cathode also show ultra-stable cycling performance over 2400 cycles at 1C in a conventional all-phenyl complex (APC) electrolyte. This facile interface modification strategy sheds light on the development of advanced RMBs and also provides a promising direction for the design of high-performance Mg-based alloy anodes for high-performance RMBs and beyond.

Dealloying of Mg-based alloys for production of self-supporting metallic nanostructures

Dealloying is a proficient technique in the fabrication of nanostructured metals, particularly nanoporous materials, with promising potential for diverse applications. However, the development of robust and self-standing nanostructured metal foils through dealloying presents significant challenges. By generating an alloy layer on the surface of the metal foil, nanostructures can be generated on the metal foil surface through subsequent dealloying. This approach utilizes the inherent flexibility and ductility of the metal foil to ensure self-support. It also allows for the tailoring of the structure and composition of the dealloyed nanostructured metal by manipulation of the phase constitution in the surface alloy layer. In this study, we report a strategy for generating alloy layers on metal foil surfaces through the thermal evaporation of magnesium (Mg) followed by annealing. Upon dealloying the surface alloy layer, we successfully obtain self-supported nanostructured metal foils. Employing copper (Cu) as an example, we demonstrate that Mg can form a Mg–Cu alloy layer on the surface of a Cu foil, where the control over the alloy layer's phase composition and thickness is achieved by adjusting the annealing duration. Furthermore, we investigated the feasibility of this method on nickel (Ni) substrates, including Ni foils and Ni foams. Moreover, by further functionalizing the resulting nanostructured Ni foil, we transformed it into Ni(OH)2/Ni foil and explored its performance in the electrocatalytic oxygen evolution reaction (OER). The resulting catalyst achieved a current density of 10 mA cm−2 at a potential of only 349 mV in a 1 M KOH solution, exhibiting a Tafel slope of 84.52 mV dec−1. Following 10 h of stability testing, the catalyst exhibited negligible degradation in performance. This study provides a convenient and versatile pathway for preparing self-supported nanostructured metals.

Characteristics of hydride electrodes using Mg-Ti-Ni-Co-Al-based alloys synthesized by mechanical milling

For Ni-MH batteries, crystalline Mg-based alloys such as MgNi, Mg2Ni, REMg12, and La2Mg17 are regarded as hopeful negative electrode materials. Even though these alloys are inexpensive and have promising discharge capacity, they hardly ever electrochemically absorb or desorb hydrogen at room temperature. In this paper, the MgNi-based Mg50-xTixNi45Al3Co2 (x = 0, 1, 2, 3, 4) alloy electrodes were fabricated. The surface of the as-cast alloys was modified by mechanical Ni coating. The nanocrystalline and amorphous Mg50-xTixNi45Al3Co2 (x = 0, 1, 2, 3, 4) + 50 wt%Ni alloys for Ni-MH batteries were prepared using mechanical ball milling. The effects of Ti content and ball milling time on the structure and electrochemical hydrogen storage properties of the alloys were investigated. The electrochemical testing reveals that the as-milled alloys can electrochemically absorb and desorb hydrogen well at room temperature. Without any activation, the milled alloys can achieve maximum discharge capacity in the first cycle. With the extension of ball milling time and the increase of Ti content, the cycle stability and discharge capacity of the alloys are significantly enhanced. The electrochemical impedance spectrum, high rate discharge ability, potentiodynamic polarization curve, and potential-step measurement all indicate that the electrochemical kinetics of the prepared alloys initially increase and subsequently decrease with the increase of Ti content, while significantly improve with the prolongation of milling time.