Magnesium Solid Solution Research Articles

Understanding thermal transport in magnesium solid solutions through first-principles approaches and machine learning feature screening

The solid solution phases have a large influence on the thermal conductivity of alloys, but the physics behind this effect is complicated. Existing works mainly utilize experimental methods to study the thermal conductivity of alloys. However, due to the coexistence of multi-phase and insufficient understanding of the microscopic property variations in different alloy systems, it remains unclear how different solute atoms can affect the thermal transport of solid solutions. In this work, we employ first-principles simulations based on the Korringa–Kohn–Rostoker coherent potential approximation method and the Boltzmann transport equation to calculate the thermal conductivity of 38 binary magnesium solid solutions with dilute solute atom concentration. Solute atoms can greatly reduce the thermal conductivity of magnesium. Phonon contribution is found to be less than 10 %. The machine learning feature screening methods are further applied to identify the key properties that influence their thermal conductivity the most. Different from the commonly used Linde's law, which states that the resistivity is proportional to the square of valence difference, the machine learning screening indicates that thermal conductivity is predominantly influenced by six features in total. Among them, the variance of the density of states of s + p, d + f orbitals at Fermi level is highly correlated to the electronic thermal conductivity of magnesium alloys. These correlations underscore the role of virtual bond states formed in magnesium alloys due to the presence of solute atoms. The developed method and uncovered physical mechanism can potentially be applied to other solid solution systems, which is an important step to achieve predictive design of high thermal conductivity metallic alloy.

STUDY OF THE TRIBOLOGICAL AND MECHANICAL PROPERTIES OF SOME BIODEGRADABLE Mg-Ca-Zn ALLOYS

Magnesium-based biodegradable alloys used in medical applications have been intensively researched throughout the years. As is well known, the biodegradability of medical alloys is improved by alloying Mg with biocompatible and non-toxic metals. According to studies, Mg, Zn, and Ca are abundant in the human body and help to the regeneration of bone tissue efficiently and effectively. Due to their biodegradability, magnesium alloys, particularly Mg–Ca–Zn alloys used to manufacture implants, reduce patient stress by eliminating the need for a second surgery. Due to magnesium alloys' similar Young's modulus (41-45 GPa) to that of natural bone, the stress shielding effect can be significantly reduced. The objective of this research is to examine the tribological and mechanical properties of a novel experimental biodegradable alloy composed of magnesium (Mg) and 0.5 wt. % Ca, with variable amounts of zinc (Zn) at 0.5, 1.5, and 3.0 wt. %, with the aim of improve the mechanical characteristics. The microstructure and mechanical characteristics were determined using light microscopy (LM), a CETR UMT-2 Tribometer, and an Instron 34SC-5 instrument. A magnesium solid solution as well as a lamellar Mg2Ca and a MgZn2 intermetallic compound were discovered as a result of this research. The tribological parameters exhibit a decrease in coefficient of friction (COF) with increasing Zn concentration and a little increase in hardness and Young modulus up to 3 wt.%.

Study on damage and cracking of Mg-Gd-Y-Ag-Zr alloys during rolling based on experimental and finite element method

Edge cracking, a common issue encountered during the rolling of magnesium alloys, holds substantial importance in determining the success of subsequent finishing processes. It serves as a pivotal parameter for evaluating the formability of rolled plates. In this particular investigation, researchers concentrated on understanding the behavior of edge cracks within the solid solution magnesium alloy designated as Mg-10Gd-3Y-2Ag-0.4Zr (expressed in weight percentage as GWQ1032K). To support this analysis, one delved into the thermal rheological characteristics of the magnesium alloy and established a mathematical relationship connecting rheological stress, strain rate, and temperature. This served as the foundation for a constitutive model tailored to the alloy. Furthermore, practical rolling experiments were conducted to examine how reductions in thickness influenced the morphology of edge cracks in rolled plates. The study also explored shifts in stress–strain behavior and microstructural changes during the deformation process. The results highlighted the substantial impact of compression levels on the magnesium alloy’s anisotropic behavior, subsequently influencing the shape of the resultant plate and the stress–strain characteristics observed during deformation. Significantly, as the rolling reduction increased, a notable increase in heat generation due to the plastic deformation of the magnesium alloy plate was observed. This heightened heat played a key role in dynamic recrystallizationand and facilitating the formation of the brittle Mg5(RE, Ag) phase. Consequently, minimizing the generation of this brittle phase emerged as a critical factor in effectively managing and controlling edge cracks in the rolling process.

Microstructure and properties of the GEWZ522K casting magnesium alloy based on the Mg–Gd–Nd–Y–Zn–Zr system

The article discusses the solidification and phase composition of the (wt.%) Mg–4.8Gd–2.1Nd–1.6Y–0.4Zn–0.6Zr (GEWZ522K) casting alloy. It is demonstrated that in the as-cast state, the alloy structure comprises primary zirconium particles, dendrites of the magnesium solid solution (αMg), and eutectic intermetallic phases located between dendritic branches. Following solution heat treatment at t = 530±5 °C, the alloy transitions into a single-phase state and can be significantly strengthened through artificial aging after quenching. It is recommended to apply alloy aging at t = 250 °C for 8–10 h or at t = 200 °C for 15–18 h. This approach leads to the maximum strengthening of the alloy, with the best mechanical properties achieved for the alloy aged at t = 250 °C. Regardless of the aging method used, the ultimate tensile strength (UTS) of the samples surpasses 300 MPa, which significantly exceeds that of commercial casting alloys according to GOST 2856-79. The measured corrosion rate for the GEWZ522K alloy is 7.5±0.4 mm/year, that slightly higher than that for the less alloyed commercial alloy ML10 (approximately 2.5 mm/year) tested under similar conditions. Furthermore, the alloy was subjected to tests for ignition resistance when in contact with air. It was observed that with continuous airflow over the specimen’s surface, ignition centers appear at t = 625 °C due to the breakdown of the oxide film, causing the alloy to nearly completely melt. Therefore, the GEWZ522K alloy can be employed as a high-strength casting alloy. However, during the operation of cast parts, particular attention must be paid to safeguarding the surface of these parts against corrosion.

Improving the mechanical properties of BN reinforced magnesium composites using vacuum sintering method

Magnesium matrix composites with BN particles at 2%, 4%, and 6% weight percentages were developed via powder metallurgy. These composites for maritime usage were created. For compacting 15 min were spent maintaining 250 megapascals at 2500 degrees Celsius. Further, this material is sintered for eight hours at 6500 degrees Celsius. The morphology of a synthetic magnesium composite was assessed using SEM. It was observed that the absence of clustering in the matrix alloy reinforcing particles allowed lamellar precipitates to develop during diffusion on the composites. With stronger and stiffer matrix alloy reinforcement, the compressive strength (23%) and hardness (18%)of magnesium composites are increased. This improvement strengthens the intermixture. Magnesium composite corrosion was evaluated in the B117 salt spray test. With reinforcement, corrosion in magnesium composites becomes better (18%) when Alpha magnesium solid solution decreases as reinforcing expands.

THE ROTARY FORGING EFFECT ON THE STRUCTURE AND PROPERTIES OF MAGNESIUM ALLOYS OF THE Mg-Y-Gd-Zr SYSTEM

The study results of the structure and mechanical properties of magnesium alloys obtained by rotary forging, similar in composition to the IMB7-1 alloy of the Mg-Y-Gd-Zr system, are presented. Mechanical properties were determined after rotary forging and after rotary forging with subsequent aging at 200 °C for up to 64 hours. The alloys were aged both immediately after rotary forging and after homogenization at 515 °C of the deformed alloys obtained. It is established that rotary forging contributes to the hardening of the studied alloys as a result of grain grinding and intensive twinning. Aging carried out after rotary forging leads to additional hardening of alloys as a result of the decomposition of supersaturated magnesium solid solution. Annealing after rotary forging increases the grain size in the studied alloys due to collective recrystallization and thereby reduces the strength properties of the alloys.

Investigation of castability, mechanical, corrosion properties and flammability of ML-OPB and EWZ43 magnesium alloys

Magnesium alloys are usually considered as structural materials when the weight reduction is important - in aircraft and space industry for example. In recent years, there has been an increase in the use of new generation ignition-proof high-strength magnesium alloys in the design of aircraft parts. The properties of new ignition-proof casting magnesium alloys ML-OPB (Mg–6.7Y–2.6Zn–0.5Zr–0.35Ce– 0.35Yb; wt.%) and EWZ43 (Mg–3.8Y–4.4Nd–0.6Zr–0.6Zn; wt.%) were investigated and compared with properties of commercial magnesium alloys. The microstructure of investigated alloys in the as-cast condition comprises of a magnesium solid solution and a significant amount of eutectic. Heat treatment according to the T6 mode results in change in the eutectic phase’s morphology and also to their partial dissolution in the magnesium matrix. Long-term high-temperature holding, simulating operating conditions (500 h at 300 °C), leads to the formation of precipitates along the grain boundaries in both alloys, significantly reducing the mechanical properties. During the oxidation of the samples, it was established that the main components that involved into the oxide film and provides the protective properties of the alloys is Y, Nd and Yb. The investigated alloys have a high strength, which is not lower than that of the ML10 alloy. At the same time, the advantage of the ML-OPB alloy is a high elongation at fracture, while the EWZ43 alloy is characterized by high strength. The corrosion rate of the investigated alloys exceeds the corrosion rate of known commercial ML10 and AZ91 alloys, which implies the need for additional protection against corrosion of investigated alloys. At the same time, the castability of ML-OPB and EWZ43 alloys is no lower than that of most commercial magnesium alloys. An oxide film with high Y content and high protective properties is formed when the alloys interact with the sand mold bonded with furan resin. The ignition temperature of the investigated alloys is 100–150 °C higher than that of the ML10 alloy. The flammability test of alloys in the flame of a gas burner, made on cone samples and typical aircraft castings «bracket», showed that ML-OPB and EWZ43 alloys are almost non-flammable under the conditions of experiment.

Textural Evolution of 6061 Aluminum Alloy Processed by Accumulative Roll-Bonding Process

A commercial Al-Mg-Si alloy (AA 6061) was deformed by using the accumulative roll bonding (ARB) process for up to five cycles at ambient temperature. The evolution of texture in this process was studied by the X-ray diffraction (XRD) method. Experimental results indicate that the combination of the shear texture composed of Rotated cube {001} component and the rolling textures that included Copper {112} and Dillamore {4, 4, 11} components developed after the first cycle. During the first cycle, the shear texture was developed as a result of shear deformation induced by high level of friction between the rolls and the sheet. By increasing the number of cycles, the shear texture strength diminished and changed to the rolling texture. After the fifth cycle, a remarkable increase in the rolling texture intensity was observed due to homogenous deformation induced by the presence of fine non-shearable particles. Additionally, the presence of magnesium in solid solution influenced the texture evolution during ARB.

Electron beam irradiation induced metastable phase in a Mg−9.8 wt%Sn alloy

Aberration-corrected scanning transmission electron microscopy has been used to study a novel metastable phase, designated as β′′ phase, induced to form by electron beam irradiation in a Mg−9.8 wt.%Sn alloy. This phase is spherical in three dimensions, having a D019 structure with the lattice parameters of a = 0.642 nm, c =0.521 nm and space group of P63/mmc. Its chemical formula is Mg3Sn, like the β′ metastable precipitate phase. The orientation relationship between the β′′ phase and the α-Mg matrix is such that [21¯1¯0]β′′ // [21¯1¯0]α and (0001)β′′ // (0001)α. Its formation involves solely the ordering of Sn atoms in the solid solution magnesium matrix. First-principles calculations indicate that the formation of the β′′ phase is energetically favored.

Post-Aging Retrogression in Magnesium Alloys with Two Rare-Earth Metals Belonging to Different Groups

The phenomenon of post-aging retrogression in magnesium alloys containing two rare-earth metals belonging to different groups, i.e., yttrium Y (the yttrium group) and samarium Sm (the cerium group), is investigated. It is shown that retrogression may occur in alloys with different proportions of yttrium and samarium aged at 200°C for maximum hardness and then annealed at somewhat higher temperatures (250 and 300°C). The process is possible due to decomposition of the supersaturated magnesium solid solution. The degree of the retrogression is shown to depend on the temperature and duration of the post-aging annealing and on the yttrium- to-samarium proportion in the alloys.

The strength increase by nano-scale particles precipitated during magnesium solid solution decomposition in magnesium alloys with the rare-earth metals of the yttrium group

Magnesium-base alloys attract a great attention as light structural materials, where economy of weight is of great importance. According to the last investigations, the highest strength properties of these alloys, can be obtained, when they contain some of the rare-earth metals. All of them belong to the yttrium group. Existence of the rare-earth metals in magnesium alloys enable to form in their structures small hard particles, which increase significantly strength of the alloys. The hard particles appear after the special heat treatments and should have the certain measurements and amounts. In this article the main results of some investigations are described, where the best conditions for the heat treatments of the magnesium alloys with high strength were established. The highest strength in the alloys was observed, when the hard particles were nano-scale in them with certain disposition in the structure.

Effect of various rare-earth metals in magnesium alloys on their strength properties

Based on the results of previously published studies, the main laws of the effect of various rare earth metals on the properties of magnesium alloys used as light structural materials are formulated. It is noted that the properties of magnesium alloys containing rare-earth metals are largely determined by their solubility in solid magnesium, which changes successively with an increase in the atomic number of these elements, as well as the tendency to harden during the decomposition of magnesium solid solutions. The possibility of improving the properties of magnesium alloys when doped with various rare-earth metals in a certain ratio is reported, and the examples of such new alloys are provided.

Joint Effect of Samarium and Holmium on the Strength Properties of Mg–Y–Gd–Zr Alloys

The joint effect of samarium and holmium on the properties of an IMV7-1 Mg–Y–Gd–Zr alloy in two different states, namely, homogenized and homogenized and subsequently aged at 200°C to the peak strength, has been studied at testing temperatures of 20 and 250°C. Samarium and holmium do not change the behavior of the Mg–Y–Gd–Zr alloys during aging; at the same time, the presence of ~4% Sm in the alloys accelerates the decomposition of the magnesium solid solution and increases their strength properties, and the presence of 2 to 5% Ho in the IMB7-1 alloys containing 4% Sm leads to a decrease in their strength properties.

Change in damping capacity arising from twin-boundary segregation in solid-solution magnesium alloys

ABSTRACT The change in twin-boundary mobility that is caused by twin-boundary segregation was investigated in pure magnesium and four binary solid-solution magnesium alloys (Mg-Ag, Mg-Sn, Mg-Y and Mg-Zn alloys). The damping capacity in the vicinity of {} twin boundaries was measured before and after annealing by nano-dynamic mechanical analysis. The subsequent annealing process led to a lower damping capacity in all magnesium binary alloys, which was in contrast to the results in pure magnesium. This is on account of the segregation of solute atoms in incoherent twin boundaries. The alloying elements, which have the characteristic of a low segregation energy for twin boundaries, effectively prevents the damping capacity degradation.

Effect of solid solution addition on the dislocation emission in aluminum alloys

Solid solution strengthening plays a key role in the strength increasing of alloying metals, due to that a solid solution of alloying element causes lattice distortion to a certain extent. In the paper, the effect of solid solution magnesium additions on the edge dislocation emission from a blunted crack tip in aluminum alloys is investigated. The critical stress intensity factor for the dislocation emission considering different magnesium solute concentrations is analyzed under the mode I and mode II loading conditions. The results show that within a certain concentration range the magnesium solute concentration does affect dislocation emission, although the influence appears not very strong. The critical stress intensity factor for the dislocation emission decreases with the increment of solute concentration. This means that relatively increasing the solute concentration can promote the dislocation emission, cause effective blunting of cracks and thus improve the fracture toughness of materials.

The Regularities in Constitution of the Ternary Phase Diagrams of Magnesium Alloys with Two Rare-Earth Metals Belonging to Different Groups (Yttrium Group or Cerium Group)

Investigations of the ternary phase diagrams of magnesium with two rare-earth metals from different groups (the yttrium group or the cerium group) are described with the main attention being paid to regions near the Mg corner. In these parts of the ternary phase diagrams, it was found that the magnesium solid solution was in equilibrium with only two binary compounds of magnesium with both rare-earth metals, and in addition, a significant solubility of each rare-earth metal in the most magnesium rich compound of the second rare-earth metal. In ternary Mg-systems involving rare-earth metals of different groups, trends in changes in the constitution in the Mg-region of the diagram as a function of the atomic number of the rare-earth additions were noted. These trends were established by comparing ternary phase diagrams of Mg-containing systems comprising yttrium and a rare-earth metal from the cerium group, and systems comprising samarium (from the cerium group) and a rare-earth metal from the yttrium group.

Effect of the Annealing Temperature on the Aging-Induced Recovery in Magnesium Alloys with Rare-Earth Metals

The possibility of recovery in binary magnesium alloys with the yttrium group rare-earth metals (Y, Gd, Tb, Dy, Ho), in which the decomposition of a supersaturated magnesium solid solution at 200°C is accompanied by substantial hardening, is studied at an annealing temperature of 300°C. Annealing at 300°C of the alloys aged at 200°C to the state with the highest hardness results in significant recovery, which is much higher than the established recovery of these alloys at an annealing temperature of 250°C. The recovery regularly changes as a function of the atomic number of a rare-earth metal. Structural analysis of the alloys suggests that the phases formed in them during hardening aging are partly retained during the subsequent recovery, and no new phases form.

Change in Damping Capacity Due to Twin Boundary Segregation in Solid Solution Magnesium Alloys

The change in twin boundary mobility due to twin boundary segregation was investigated in pure magnesium and four binary solid solution magnesium alloys. The damping capacity in the vicinity of {10-12} twin boundaries were measured before and after annealing by nano-dynamic mechanical analysis. The annealing led to lower damping capacity in all magnesium alloys, which was in contrast to the results in pure magnesium. This is caused by the segregation of solute atoms in incoherent twin boundaries. The alloying element that has a characteristic of low segregation energy for twin boundaries effectively prevented the damping capacity degradation.

Effect of Holmium and Ytterbium on Age Hardening of High-Strength Magnesium Alloy IMV7-1 of the Mg – Y – Gd – Zr System

The kinetics of decomposition of supersaturated magnesium solid solution and of the accompanying hardening of the latter at 200°C in cast alloy IMV7-1 of the Mg – Y – Gd – Zr system alloyed with two rare-earth metals, i.e., holmium and ytterbium, is studied. Holmium and ytterbium are introduced into IMV7-1 by substituting two other rare-earth metals, i.e., yttrium and gadolinium. It is shown that the presence of holmium and ytterbium instead of yttrium and gadolinium does not change the decomposition behavior of the supersaturated solid solution but decelerates this process and lowers the effect of age hardening.

Aging-Induced Recovery of Magnesium Alloys with Various Rare-Earth Metals

The aging-induced recovery of binary magnesium alloys with various rare-earth metals (Y, Nd, Sm, Gd, Tb, Dy, Ho), in which the decomposition of the supersaturated magnesium solid solution is accompanied by substantial hardening, is studied. It is found that annealing of the alloys at 250°C, which were preliminary aged at 200°C to a peak hardness, leads to their softening; in this case, the hardness continues to decrease as the annealing time increases. Electrical resistivity measurements show that, as a result of annealing at 250°C, recovery takes place and is accompanied by partial dissolution of the decomposition products in the magnesium solid solution; after that, its decomposition continues. The degree of recovery in the alloys with yttrium-group rare-earth metals (Y, Gd, Tb, and Ho) is found to be higher than that for the alloys with cerium-group rare-earth metals (Nd and Sm); within the lanthanide series, the degree of recovery increases with the atomic number of a rare-earth metal.