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• A High-throughput screening workflow to investigate the corrosion properties of binary mg alloys is developed. • Several intermetallics, e.g. Y 3 Mg, Y 2 Mg and La 5 Mg, are identified to be promising intermetallics which might effectively hinder the cathodic HER. • Machine learning models are applied to predict the hydrogen adsorption energy of Mg intermetallics, which can accelerate the high-throughput screening process. Magnesium (Mg) alloys have shown great prospects as both structural and biomedical materials, while poor corrosion resistance limits their further application. In this work, to avoid the time-consuming and laborious experiment trial, a high-throughput computational strategy based on first-principles calculations is designed for screening corrosion-resistant binary Mg alloy with intermetallics, from both the thermodynamic and kinetic perspectives. The stable binary Mg intermetallics with low equilibrium potential difference with respect to the Mg matrix are firstly identified. Then, the hydrogen adsorption energies on the surfaces of these Mg intermetallics are calculated, and the corrosion exchange current density is further calculated by a hydrogen evolution reaction (HER) kinetic model. Several intermetallics, e.g. Y 3 Mg, Y 2 Mg and La 5 Mg, are identified to be promising intermetallics which might effectively hinder the cathodic HER. Furthermore, machine learning (ML) models are developed to predict Mg intermetallics with proper hydrogen adsorption energy employing work function (W f) and weighted first ionization energy (WFIE). The generalization of the ML models is tested on five new binary Mg intermetallics with the average root mean square error (RMSE) of 0.11 eV. This study not only predicts some promising binary Mg intermetallics which may suppress the galvanic corrosion, but also provides a high-throughput screening strategy and ML models for the design of corrosion-resistant alloy, which can be extended to ternary Mg alloys or other alloy systems. [ABSTRACT FROM AUTHOR]

To serve in a more aggressive chlorine (Cl−) ions-containing environment, a chlorine ions insensitivity Mg-Nd-Zr alloys is fabricated, exhibiting a stable corrosion resistance in either 3.5wt.% or 10 wt.% NaCl solution. Unlike pure Mg who exhibit a negligible protection of the matrix, a distinct "hindering effect" of Cl− diffusion caused by doping elements within the corrosion film was observed. Its underlying mechanism is demonstrated by X-ray photoelectron spectroscopy (XPS) and Density functional theory (DFT) analysis. The introducing with Nd and Zr elements can effectively passivate vacancies and alter diffusion energy of chlorine ions. [ABSTRACT FROM AUTHOR]

Mathematical models were proposed to clarify the effect of alloying on corrosion of magnesium alloys based on film-free and film-covered status. The models are applicable to explain the "barrier effect" by cathodes and the "analogous Hall-Petch relationship" between corrosion rates and grain size. The slope of corrosion rates versus alloying content is determined by the dissolution ability of film-free substrate and the hindering effects by corrosion product film. Designing strategy for corrosion-resistant Mg alloys is established. [ABSTRACT FROM AUTHOR]

Magnesium alloys with high strength and excellent corrosion resistance are always sought-after in light-weighting structural components for automotive and aerospace applications. However, for most magnesium alloys that have a high specific strength, they usually have an inferior corrosion resistance and vice versa. In this work, we successfully develop a Mg-11Y-1Al (wt. %) alloy through conventional casting, solution treatment followed by extrusion. The overall properties of this alloy feature with a corrosion rate lower than 0.2 mm y−1, high yield strength of 350 MPa and moderate tensile elongation of 8%, the combination of which shows competitive advantage over other comparative magnesium alloys in the literature. It is found that a thin and dense protective film of Y2O3/Y(OH)3 can be fast developed with the aid of Al2O3/Al(OH)3 deposition to isolate this alloy from further attack of corrosion medium. Meanwhile, the refined grains, weak texture and activation of non-basal slip systems co-contribute to the high strength and good ductility. Our findings are expected to inspire the design of next-generation high performance magnesium alloys. High-strength Mg alloys are often sought-after for automotive and aerospace applications, but they have an inferior corrosion resistance. Here, the authors develop a Mg-11Y-1Al (wt. %) alloy that shows both significantly improved mechanical properties and corrosion resistance. [ABSTRACT FROM AUTHOR]

The role of alloyed Sc on the corrosion behavior of Mg was revealed using an understanding of the anodic and cathodic kinetics derived from experimental measurements and DFT calculations. After T4 solution treatment, the Mg–Sc alloy exhibited higher corrosion resistance than high pure Mg. The scandium oxide-rich surface layers formed on the T4 Mg–Sc alloy seemed to suppress anodic dissolution by being protective, and the addition of Sc could inhibit cathodic hydrogen evolution. [ABSTRACT FROM AUTHOR]

With the help of density functional theory (DFT) calculations, Mg-Sc-Y alloys with various Y content were designed and produced. The single-phase Mg-Sc-Y alloys were composed of a typical peritectic microstructure with internal Sc-rich zones surrounded by Y-rich zones. With increasing Y content, the hydrogen evolution rates decreased significantly to 0.13 mL/cm2/day and increased slightly afterward. This was attributed to the combined effect of a decrease in the thermodynamic driving force for corrosion, surface layer improvement, and an increase in the number of galvanic couples between the Sc-rich and Y-rich zones. [ABSTRACT FROM AUTHOR]

Mg alloys containing long-period stacking-ordered (LPSO) phases often display excellent mechanical properties. The underlying mechanism is yet unclear. In this work, in situ synchrotron X-ray diffraction was employed to study tensile deformation of a Mg97Y2Zn alloy that contains 18R-type LPSO phase. From lattice strain measurement, it is found that the LPSO phase has a similar elastic modulus as Mg. After material yielding, lattice strain in the Mg phase decreased, while lattice strain in the LPSO phase increased further. By analyzing the lattice strain evolution of different Mg peaks, basal slip and deformation twinning are identified as the dominant deformation mechanisms. This finding is further confirmed by surface slip trace analysis using electron backscattered diffraction (EBSD). Additional analysis of diffraction peak broadening indicates a continuous increase of dislocation density during plastic deformation. Based on the above results, it can be concluded that the interdendritic LPSO phase behaves like a reinforcing phase that directly strengthens the material. The high tensile ductility of the material is attributed to the weak extrusion texture caused by the presence of interdendritic LPSO. In addition, small LPSO plates inside the Mg phase can serve as dislocation nucleation sites, which leads to a high work hardening rate in the material. [ABSTRACT FROM AUTHOR]

Poor corrosion property has been a bottleneck problem during the application of Mg alloys. This work proposes a new way to improve the corrosion resistance of MgNd alloy by micro-alloying Zr, which promotes the precipitation process to rapidly form a protective corrosion layer. The corrosion rate decreases by three orders of magnitude from 32.69 mL/cm2/day to 0.072 mL/cm2/day. The results show Zr tends to form nano-scale oxide clusters on Mg surface, acting as pre-precipitation sites to accelerate the precipitation and facilitate the formation of dense and compact corrosion layer. [Display omitted] • Via micro-alloying Zr, the corrosion rate of Mg-Nd alloy decreases by three orders of magnitude to 0.072 mL/cm2/d. • The formation process of the corrosion layer was monitored and clarified by in-situ AFM and EN technique. • The oxide of Zr can act as pre-precipitate sits to accelerate the precipitation rate, leading to a dense and compact corrosion layer. [ABSTRACT FROM AUTHOR]

The effects of the volume ratios of micro and nano-SiC particles (SiCp) on the grain refinement, distribution of SiCp particle, and tensile properties of the as-cast AZ31B (Mg-3Al-1Zn-0.3Mn) magnesium-based metal matrix composites have been investigated. As the volume fraction of micron SiCp decreases to 9 vol.% and the nano-SiCp increases to 1 vol.%, excellent grain refinement effect is achieved. This is due to both the uniform distribution and refining effects of micro- and nano-SiCp. Moreover, the micron SiCp distribute along the grain boundaries, while nano-SiCp is mainly distributed around the micron SiCp. The room-temperature tensile results show that the optimal room-temperature yield and tensile strengths are achieved with a 9/1 ratio of micro to nano-SiCp, while the 9.5/0.5 ratio yielded the highest elongation. [ABSTRACT FROM AUTHOR]

The electrical resistivity and thermal conductivity of some Mg–Al, Mg–Zn and Mg–Mn binary magnesium alloys were measured in the temperature range of 2–300 K. The electrical resistivity increased with the increasing alloying content in each binary alloy system, while the thermal conductivity exhibited an opposite trend. The low-temperature thermal conductivity was understood using κ = ( A / T + BT 2 ) −1 + CT 2 , which is found to be applicable in various binary and/or multi-component alloy systems. The parameters A , B and C were determined through numerical fitting of the experimental data. Significant differences were found in the effect of three solute atoms on the thermal conductivity of Mg. The reasons for large differences in the thermal conductivity of the three binary magnesium alloy systems are discussed. Variations in the atomic volume and the valence are believed to play an important role on the thermal conductivity of magnesium alloys. [ABSTRACT FROM AUTHOR]

The effect of microalloying Sc on the microstructure and mechanical properties of Al–Zn–Mg–Cu alloys was experimentally investigated through X-ray diffraction, optical microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy characterizations and tensile tests. The presence of Sc caused the formation of the primary Al 3 Sc phase and behaved a significant modifying effect on the cast microstructure with an equiaxed microstructure attained in the Sc-bearing alloys rather than the dendrites in Sc-free alloys. In the subsequent thermal extrusion processing, a remarkable grain refinement and retardation of recrystallization occurred, because the nano-sized Al 3 Sc dispersoids contributed to the pinning effect on the dislocation movement and grain boundary migration in the Sc-bearing alloys. The mechanical properties were significantly improved with the addition of Sc. The superior comprehensive mechanical properties in the Sc-bearing alloys were achieved via the optimal extrusion at 350 °C with the yield strength and ultimate tensile strength of 373.7 ± 3 MPa and 490.3 ± 5 MPa, respectively. The strong strengthening behavior of the Sc addition in the extruded alloys is mainly attributed to the grain refinement and the dispersoid strengthening from the Al 3 Sc particles. The corresponding contributions to the increase in yield strength derived from the grain refinement and the dispersoid strengthening were estimated, which indicated that the highest particle density attained by extrusion at 350 °C resulted in the excellent mechanical properties of the Sc-bearing alloys. [ABSTRACT FROM AUTHOR]

Magnesium alloy is a promising material for light-weight bipolar plates of proton exchange membrane fuel cell (PEMFC) owing to its low density, but high susceptibility to corrosion limits the application. In this paper, a novel hydrophobic Polytetrafluoroethylene (PTFE)/Carbon cloth/Ag multilayer coating is fabricated on Mg substrate. Potentiodynamic polarization results reveal that the multilayer coating decreases the corrosion current density of bare Mg dramatically from 17.24 μA/cm2 to 0.058 μA/cm2, meanwhile, the interfacial contact resistance (ICR) between carbon paper and coated magnesium drops from 100.6 mΩ cm2 to 27.28 mΩ cm2 at 1.4 MPa. The mechanism of the superior corrosion resistance and electrical property of coated Mg is discussed, which may shed light on the development of the novel light-weight magnesium bipolar plates of PEMFC. Image 1 • Novel hydrophobic PTFE/Carbon cloth/Ag coating is developed for Mg bipolar plates. • Corrosion current density drops from 17.24 μA/cm2 to 0.058 μA/cm2 after coating. • The ICR of PTFE/Carbon cloth/Ag coated Mg is only one-third of that for bare Mg. • Superior anti-corrosion and electrical property is obtained by the novel coating. [ABSTRACT FROM AUTHOR]

The influences of solute atoms (Li, Al, Mn, Zn, Fe, Ni, Cu, Y, Zr) and Cl adsorption on the anodic corrosion performance on Mg (0001) surface have been investigated based on first-principles calculations, which might be useful for the design of corrosion-resistant Mg alloys. Work function and local electrode potential shift are chosen as descriptors since they quantify the barrier for charge transfer and anodic stability. We found that at 25% surface doping rate, Y decreased the work function of Mg, while the impact of remaining doping elements on the work function of Mg was trivial due to the small surface dipole moment change. The adsorption of Cl destabilized the Mg atoms at surface by weakening the bonding between surface Mg atoms. We find that a stronger hybridization of d orbits of alloying elements (e.g. Zr) with the orbits of Mg can greatly increase the local electrode potential,which even overbalances the negative effect introduced by Cl adsorbates and hence improves the corrosion resistance of Mg alloys. [ABSTRACT FROM AUTHOR]

Thermal conductivities of Mg Nd alloys in as-cast, T4 and T6 conditions with Nd content varying from 0 to 12 wt% were studied at room temperature, and corresponding microstructures observation and hardness tests were performed. The as-cast Mg Nd alloys consist of α-Mg and Mg 12 Nd phases, while Mg 12 Nd dissolves into α-Mg matrix or transforms to Mg 41 Nd 5 after T4 treatment. T6 treated Mg Nd alloys are composed of α-Mg and Mg 41 Nd 5 phases. With increasing Nd content, thermal conductivities of Mg Nd alloys all decrease gradually under as-cast, T4 and T6 conditions. The thermal conductivity of as-cast Mg Nd alloys is higher than that of T4 counterparts, while lower than that of corresponding T6 alloys. For T4 alloys, the changes in slopes of Nd content dependence of thermal diffusivity and hardness all occur around the saturated point 0.68 at.% (3.87 wt%), which result from no more Nd atoms dissolved into the Mg matrix with increasing Nd content. Quantitative studies about the influence of solution atoms and second phases on thermal diffusivity were made. The thermal diffusivity increment derived from one atom percentage of Nd addition into the Mg matrix is about 67.24 mm 2 /s while the increment derived from one atom percentage of Nd addition forming second phase is about 11.85 mm 2 /s. [ABSTRACT FROM AUTHOR]

A highly corrosion-resistant AW90 extruded alloy (Mg-9Al-0.2Y wt %) was developed via alloying and solution-aging treatment (P W = 0.14 mm/y). The solution-treated AW90 alloy exhibits the most severe localized corrosion due to the strong micro-galvanic acceleration effects. The finely dispersed Mg 17 Al 12 phase promotes the strong quasi-passive behavior and uniform corrosion of the aged AW90 alloy due to the formation of a dense and uniform corrosion product film. The high corrosion resistance of the aged AW90 alloy is attributed to the formation of a Mg-Al layered double hydroxide film, which has stronger resistance to chloride ions. [Display omitted] • A highly corrosion-resistant AW90 extruded alloy was developed via alloying and solution-aging treatment. • The aged AW90 alloy exhibits an extremely low corrosion rate of 0.14 mm/y. • The uniformly dispersed Mg 17 Al 12 precipitates promote the uniform corrosion of AW90 alloy. • Mg-Al layered double hydroxide film leads to high corrosion resistance of aged AW90 alloy. [ABSTRACT FROM AUTHOR]

This work performed a CALPHAD-guided design strategy to develop high strength-ductility Mg–Y–Al alloy by taking advantage of the strengthening effect of the LPSO phase and the ductilizing effect of the α-Mg matrix. To achieve this goal, the LPSO phase content and the Y content in the α-Mg matrix were quantitatively optimized via calculations of the isoplethal section and phase fraction diagrams. Based on this, three typical Mg-Y-Al alloys without the LPSO phase and with varying LPSO contents were designed. The strength of the alloys was significantly improved by the introduction of the LPSO phase and the increase in its content. However, the ductility of the alloy was maintained while increasing the LPSO content. Through analyzing the strengthening and ductilization mechanisms, it was revealed that the LPSO phase can strengthen the extruded alloys by refining the dynamic recrystallized grain size, exerting a short-fiber-like strengthening effect, and dislocations strengthening effect by hindering dislocations movements. The ductile α-Mg phase with considerable Y content can effectively withstand plastic strain by operating multiple slips during the deformation, significantly improving the ductility of the material. The results of this study inspired the development of an effective design strategy to produce high strength-ductility Mg-Y-Al alloys by quantitatively optimizing the LPSO phase and Y contents in the α-Mg matrix, as well as to design high-performance Mg alloys for engineering demands in the future. [Display omitted] [ABSTRACT FROM AUTHOR]

Magnesium (Mg) alloys can potentially be widely applied in transportation, aerospace and biomedical fields due to the light weight and biocompatibility. However, they are usually subjected to serious galvanic corrosions due to high chemical activity. In this work, active learning is employed to discover the intermetallic compounds which can suppress the corrosion cathodic reaction of Mg alloys. The hydrogen adsorption energy, which is a descriptor for the rate of the cathodic hydrogen evolution reaction (HER), is predicted by machine learning models using the geometric and chemical features of the H adatom's Voronoi neighbors. After five active learning iterations, the prediction error of the H adsorption energy for the strong/weak adsorption configuration is 0.196 eV (MAE) with the training set size less than 1% unknown data set. Furthermore, we find that the surfaces with strong H adsorption transfer more electrons to H adatoms than the weak H adsorption surfaces. Finally, the ability of the binary Mg intermetallics to inhibit the HER is ranked according to their surface stabilities and predicted H adsorption energies. This work suggests the binary Mg intermetallics that could greatly suppress the corrosion cathodic reaction through active learning and density functional theory (DFT) simulations, which is expected to accelerate the design of corrosion-resistant Mg alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the room temperature thermal conductivity and microstructure of Mg−Ce, Mg−Sm and Mg−Y binary alloys in as-cast and solution treated conditions were investigated. Quantitative study was conducted on the effect of rare earth elements (in solid solution and intermetallic compounds) on the thermal conductivity of Mg−RE alloys. The reduction in thermal conductivity was determined to be about 123.0 W/(m·K) and 6.5–16.4 W/(m·K), respectively, per 1 at.% RE addition in the form of solid solution or intermetallic compounds with Mg. The thermal conductivities of Mg−RE alloys were fitted using modified Maxwell and EMT models based on the distribution, volume fractions and shape of intermetallic compounds. The modified structural models provide a good fit to the experimental thermal conductivity data. [ABSTRACT FROM AUTHOR]

Mg-Y based alloys exhibit a promising combination of strength and deformability through tuning precipitation and solute strengthening mechanisms and tailoring the activity of non-basal dislocations. Understanding the precipitation sequence of Mg-Y based alloys and its dependence on Yttrium concentration in the matrix will provide a guideline for fine tuning structure, morphology and distribution of precipitates in Mg-Y based alloys. In this paper, we explore the precipitation behaviors of Mg-11Y (wt%) and Mg-11Y-1Al (wt%) alloys using aberration-corrected scanning transmission electron microscopy, and rationalize the experimental observations based on first-principles density functional theory calculations. The precipitation sequence during ageing at 225 °C is identified to be SSSS → clusters/G.P. Zones → β ′ (Mg 7 Y) → β ′′/ β t ′′ (Mg 3 Y). A novel β t ′′ phase forms through in-situ transformation from the β ′ phase, which shares the same Mg 3 Y composition with D0 19 - β ′′ phase and exhibits the same cbco -structure as β ′ phase in Mg-Y based alloys. [Display omitted] • A new precipitation sequence, SSSS → clusters/G.P. Zones → β ′ (Mg 7 Y) → β ′′/ β t ′′ (Mg 3 Y), is observed in Mg-Y based alloys. • The β t ′′ phase, which has a Mg 3 Y composition and a cbco structure, is in-situ transformed from the β ′ phase. • The β t ′′ phase is stable after long-time exposure at elevated temperature. [ABSTRACT FROM AUTHOR]