Properties Of Mg Alloys Research Articles

Reaction-tunable diffusion bonding to multilayered Cu mesh/ZK61 Mg foil composites with thermal conductivity and lightweight synergy

• Reaction-tunable diffusion bonding (RDB) was proposed. • The indenter displacement was utilized to quantify the reactive diffusion degree with adjustable, visible, and high flexibility. • Multilayered Cu mesh/ZK61 Mg foil composites exhibited thermal conductivity and lightweight synergy. • Hasselman–Johnson model and Rayleigh model were applied to quantitatively scrutinize the thermal conductivity. The thermal properties of Mg alloys require further optimization to encounter the increasingly severe heat dissipation demands of high-power densities and highly integrated electronic components. In this study, a novel strategy of reaction-tunable diffusion bonding (RDB) was applied to manipulate the interfacial reaction in the multilayered Cu mesh/ZK61 Mg foil composites. The displacement of the punch was utilized to quantify the degree of reactive diffusion with adjustable, visible, and high flexibility. The interface was artificially manipulated to produce the fluid Mg–Zn eutectic liquid phase filling the interfacial gap at high temperature for a short time, followed by diffusion bonding at low temperature. The thermal conductivity of the composites first increased and then decreased, which was synthetically affected by the amelioration of metallurgical bonding and the moderately reactive consumption of Cu. The reinforcement Cu was converted from the Hasselman–Johnson model to the Rayleigh model, reflecting the optimization of the interfacial bonding quality. The composites with thermal conductivity and lightweight synergy were fabricated successfully. Therefore, RDB is a progressive technique, shedding lights on the innovative lightweight metal matrix composites with high thermal conductivities relevant to the 5G communications and new energy vehicle industries.

Mechanical and Corrosion Properties of Mg–Gd–Cu–Zr Alloy for Degradable Fracturing Ball Applications

Generally, excellent mechanical properties of Mg alloys are desired, but their rapid degradation properties are seldom utilized. Petroleum fracturing techniques are required to take full advantage of this rapid degradation. Therefore, we have prepared an as-extruded Mg–6.0Gd–1.2Cu–1.2Zr (wt.%) alloy and treated it with peak aging to analyze its potential as a degradable fracture ball. The results show that the as-extruded alloy mainly consists of an α-Mg matrix, second phase, and large elongated α-Mg grains (LEGs). After aging, the LEGs undergo static recrystallization, which improves the mechanical properties of the alloy, and a lamellar long period stacking ordered (LPSO) phase is observed. Under simulated underground temperature conditions (93 °C), the ultimate tensile strength and elongation of both as-extruded and as-aged alloys are over Ȧ MPa and 11.1%, respectively, and the ultimate compressive strength and elongation of both alloys are over 336 MPa and 16.9%, respectively. The corrosion rate of the as-extruded alloy in 3 wt.% KCl solution at 93 °C reaches 1660.8 mm/y by mass loss test, and that of the as-aged alloy increases to 1955.1 mm/y. The atomic force microscope analysis result confirms that the second phase shows the highest corrosion potential, followed by the lamellar LPSO phase and α-Mg matrix. The as-extruded and as-aged Mg–6.0Gd–1.2Cu–1.2Zr alloy with good mechanical properties and a high corrosion rate in this work shows promising potential for degradable fracturing ball applications.

Ductility enhancement by activating non-basal slip in as-extruded Mg alloys with dilute Sc addition

This work systematically investigates the impact of the dilute Sc addition on microstructures and mechanical properties in Mg alloys. Electron back scattered diffraction, slip traces analysis, transmission electron microscopy, and visco-plastic self-consistent polycrystal constitutive (VPSC) modeling were performed to investigate the deformation mechanisms in the tensile testing, especially the activation of <c+a> slip. The results showed that as-solid solution samples only consisted of α-Mg phase. After extrusion, all samples exhibited a similar average grain size. With the increment of the Sc content, the ductility of the samples was significantly improved, which failure elongation (FL) of Mg-xSc (x = 0.3, 0.6, 0.9 wt.%) alloys improved from 14.4% to 24.8%. The yield strength of each alloy is similar, about 200 MPa. VPSC results indicated that the difference value of the initial slip resistance (τ0) between prismatic slip and basal slip decreases from 63 MPa to 49 MPa, and the difference value of τ0 between pyramidal slip and basal slip decreases from 72 MPa to 57 MPa. The VPSC and the two-beam diffraction results confirmed that the pyramidal <c+a> slip and prismatic <a> slip were activated in tensile testing. The quantitative analysis of the slip trace line verified that the volume of non-basal slip reached 49.5% when the Sc content increased to 0.9 wt.%. Therefore, the addition of Sc in solid solution increased the amount of pyramidal <c+a> and prismatic <a> dislocation activities during the deformation process, which was beneficial to coordinate the c-axis strain, and finally improved ductility of Mg alloy.

Enhanced anti-corrosion/wear properties of Mg alloy through a hierarchical bio-inspired self-healing composite coating

The poor anti-corrosion/wear property of magnesium (Mg) alloys has limited their industrial applications. This paper reports a hierarchical bio-inspired composite coating on Mg alloy surface, through a spray/spin assisted self-assembly process, which overcomes the difficulty in coordination of the self-healing and wear resistance ability, realizing an enhanced self-healing and anti-corrosion/wear ability. The nitrogen-ligated boroxine cross-linked polydimethylsiloxane (N-B-PDMS) and the blend solution of reduced graphene oxide (RGO) and polyvinyl alcohol (PVA) are used to construct the protective hard top layer and self-healing down layer, respectively, obtaining an N-B-PDMS@RGO/PVA (B@RGO/PVA) coating. A large number of reversible covalent boroxine(B3O3)/hydrogen bonding networks are formed within the coating, leading to a compact hierarchical composite structure. The results show that the scratch is miraculously repaired within 1.5 min due to the reversible chemical bonding of N-B-PDMS coating, while its tight three-dimensional network structure significantly restore the corrosion resistance of Mg alloy. The wear resistance of N-B-PDMS extremely promotes two orders of magnitude, derived from the high hardness and low friction coefficient of PVA/RGO shell, and further improves the anti-corrosion through this layer-by-layer barrier structure. Owing to the intensive self-healing ability of typical boroxine cross-linked microstructure, artificial damage of B@RGO/PVA coating can be rapidly repaired after 5 min, which surpasses almost the vast majority of previously reported self-healing materials, and therefore the long-term corrosion resistance is almost completely recovered. In this hierarchical microstructure, the top layer and the down layer complement each other to form a multi-functional coating with ultra-fast self-healing and superior corrosion/ wear resistance, which has guiding significance for the design and construction of multifunctional protection coatings for Mg alloy or other metallic materials.

Effects of sonication amplitude on the microstructure and mechanical properties of AZ91E magnesium alloy

Light metals are gaining increased attention due to ecological sustainability concerns and strict emission regulations. Magnesium (Mg) is one such metal that has the potential to replace high density components, which can reduce emissions through lightweighting. However, the mechanical properties of Mg alloys must be improved for them to become viable candidates for structural applications. To this end, the current study examines the effect of sonication vibrational amplitude on the microstructure and mechanical properties of AZ91E Mg alloy. The molten alloys were subjected to ultrasonic treatment at a frequency of 20 kHz, 180 s of processing time and vibrational amplitudes ranging from 1.25 to 15 µm. The resultant castings were characterized using optical microscopy, scanning electron microscopy and tensile testing. It was found that sonication with amplitudes up to 7.5 µm was able to effectively refine the secondary phases of the alloy. Similar trends were observed for grain size and yield strength. The refinement in microstructure was likely caused by the finer grain size and cavitation induced undercooling of the liquid metal. In addition, it was also noted that even the lowest level of amplitude (1.25 µm) was able to increase the density, improve the ultimate tensile strength and ductility of the castings. The tensile strength and ductility were thought to have been enhanced by ultrasonic degassing and refinement in microstructure, while the yield strength was improved through the Hall-Petch effect. The results from this study provided a basis for optimizing the sonication process and promoting its use in industry. As a result, Mg alloys improved through ultrasonic processing have the potential to replace higher density components, with consequent energy efficiency and environmental and ecological benefits.

Comprehensive review of additively manufactured biodegradable magnesium implants for repairing bone defects from biomechanical and biodegradable perspectives.

Bone defect repair is a complicated clinical problem, particularly when the defect is relatively large and the bone is unable to repair itself. Magnesium and its alloys have been introduced as versatile biomaterials to repair bone defects because of their excellent biocompatibility, osteoconductivity, bone-mimicking biomechanical features, and non-toxic and biodegradable properties. Therefore, magnesium alloys have become a popular research topic in the field of implants to treat critical bone defects. This review explores the popular Mg alloy research topics in the field of bone defects. Bibliometric analyses demonstrate that the degradation control and mechanical properties of Mg alloys are the main research focus for the treatment of bone defects. Furthermore, the additive manufacturing (AM) of Mg alloys is a promising approach for treating bone defects using implants with customized structures and functions. This work reviews the state of research on AM-Mg alloys and the current challenges in the field, mainly from the two aspects of controlling the degradation rate and the fabrication of excellent mechanical properties. First, the advantages, current progress, and challenges of the AM of Mg alloys for further application are discussed. The main mechanisms that lead to the rapid degradation of AM-Mg are then highlighted. Next, the typical methods and processing parameters of laser powder bed fusion fabrication on the degradation characteristics of Mg alloys are reviewed. The following section discusses how the above factors affect the mechanical properties of AM-Mg and the recent research progress. Finally, the current status of research on AM-Mg for bone defects is summarized, and some research directions for AM-Mg to drive the application of clinical orthopedic implants are suggested.

Biodegradable Mg-Sc-Sr Alloy Improves Osteogenesis and Angiogenesis to Accelerate Bone Defect Restoration.

Magnesium (Mg) and its alloys are considered to be biodegradable metallic biomaterials for potential orthopedic implants. While the osteogenic properties of Mg alloys have been widely studied, few reports focused on developing a bifunctional Mg implant with osteogenic and angiogenic properties. Herein, a Mg-Sc-Sr alloy was developed, and this alloy's angiogenesis and osteogenesis effects were evaluated in vitro for the first time. X-ray Fluorescence (XRF), X-ray diffraction (XRD), and metallography images were used to evaluate the microstructure of the developed Mg-Sc-Sr alloy. Human umbilical vein/vascular endothelial cells (HUVECs) were used to evaluate the angiogenic character of the prepared Mg-Sc-Sr alloy. A mix of human bone-marrow-derived mesenchymal stromal cells (hBM-MSCs) and HUVEC cell cultures were used to assess the osteogenesis-stimulating effect of Mg-Sc-Sr alloy through alkaline phosphatase (ALP) and Von Kossa staining. Higher ALP activity and the number of calcified nodules (27% increase) were obtained for the Mg-Sc-Sr-treated groups compared to Mg-treated groups. In addition, higher VEGF expression (45.5% increase), tube length (80.8% increase), and number of meshes (37.9% increase) were observed. The Mg-Sc-Sr alloy showed significantly higher angiogenesis and osteogenic differentiation than pure Mg and the control group, suggesting such a composition as a promising candidate in bone implants.

Hydrogen generation performances and electrochemical properties of Mg alloys with 14 H long period stacking ordered structure

Hydrolysis of Magnesium with water is an excellent way to produce H2 at high rate, especially when alloyed with nobler elements that accelerate its corrosion. In this work, the hydrogen generation properties of four Magnesium based alloys with Long Period Stacking Ordered (14 H-LPSO) structures (Mg91Cu4Y5; Mg91Ni4Y5; Mg91Ni4Gd5 and Mg91Ni4Sm5) are studied through standard electrochemical methods. The hydrolysis experiment on coarse powder are coherent with the electrochemical measurements performed on polished surface. The rare earth (Y, Gd or Sm) and transition metal (Ni or Cu) involved in the LPSO are found to have a significant influence on the corrosion and hydrolysis properties of alloys with 14 H-LPSO structures.

A Study on the Structure and Biomedical Application Characteristics of Phosphate Coatings on ZKX500 Magnesium Alloys.

Magnesium-matrix implants can be detected by X-ray, making post-operative monitoring easier. Since the density and mechanical properties of Mg alloys are similar to those of human bones, the stress-shielding effect can be avoided, accelerating the recovery and regeneration of bone tissues. Additionally, Mg biodegradability shields patients from the infection risk and medical financial burden of needing another surgery. However, the major challenge for magnesium-matrix implants is the rapid degradation rate, which necessitates surface treatment. In this study, the ZKX500 Mg alloy was used, and a non-toxic and eco-friendly anodic oxidation method was adopted to improve corrosion resistance. The results indicate that the anodic coating mainly consisted of magnesium phosphate. After anodic oxidation, the specimen surface developed a coating and an ion-exchanged layer that could slow down the degradation and help maintain the mechanical properties. The results of the tensile and impact tests reveal that after being immersed in SBF for 28 days, the anodic oxidation-treated specimens maintained good strength, ductility, and toughness. Anodic coating provides an excellent surface for cell attachment and growth. In the animal experiment, the anodic oxidation-treated magnesium bone screw used had no adverse effect and could support the injured part for at least 3 months.

Corrosion behavior of severely plastically deformed Mg and Mg alloys

Magnesium (Mg) alloys have several advantages, such as low density, high specific strength and biocompatibility. However, they also suffer weak points, such as high corrosion, low formability and easy ignition, which makes their applications limited. Many studies have been conducted to overcome these disadvantages and further improve the advantages of Mg alloys. Severe plastic deformation (SPD) is one of the most important techniques and has great effects on the microstructure refinement of Mg alloys and improvements in their strength and formability. Several researchers have studied the corrosion behavior of SPD-processed Mg alloys in recent decades. However, these studies have reported some controversial effects of SPD on the corrosion of Mg alloys, which makes the research roadmap ambiguous. Therefore, it is important to review the literature related to the corrosion properties of Mg alloys prepared by SPD and understand the mechanisms controlling their corrosion behavior. Effective grain refinement by SPD improves the corrosion properties of pure Mg and Mg alloys, but control of the processing conditions is a key factor for achieving this goal because texture, dislocation density, size and morphology of secondary phase also importantly affects the corrosion properties of Mg alloys. Reduced grain size in the fine grain-size range can decrease the corrosion rate due to the increased barrier effect of grain boundaries against corrosion and the formation of a stable passivation layer on the surface of fine grains. Basal texture reduces the corrosion rate because basal planes with the highest atomic planar density are more corrosion resistant than other planes. Increased dislocation density after SPD deteriorates the corrosion resistance of the interior grains and thus proper annealing after SPD is important. The fine and uniform distribution of secondary phase particles during SPD is important to minimize the micro-galvanic corrosion effect and retain small grains during annealing treatment for removing dislocations.

The microstructural, textural, and mechanical effects of high-pressure torsion processing on Mg alloys: A review

Magnesium (Mg) alloys attract considerable attention in the fields of aerospace, defense technology, and automobile production, owing to the advantages of their low density, their highly specific strength/stiffness, and their good damping and electromagnetic shielding performance. However, low strength and poor ductility limit further application. Severe plastic deformation is considered the most promising means of producing ultrafine-grained Mg alloys and improving their mechanical properties. To this end, high-pressure torsion (HPT) is one of the most effective techniques. This article outlines the microstructure, texture, and mechanical properties of Mg alloys processed using HPT. The effects of deformation parameters, such as processing temperature, turns, applied pressure, and rotation speed, on the grain refinement and secondary phases are discussed. Textural evolution is detailed in light of both intrinsic and extrinsic factors, such as cumulative strain and the composition of the alloy elements. The subsequent enhancement of mechanical properties and mechanisms, and the significant contribution of the HPT process to strength are further reviewed. Given the advantages of HPT for grain refinement and structural modification, researchers have proposed several novel processes to extend the industrial application of these alloys.

Effect of amorphous phase on the migration mechanism of basal/prismatic interface in Mg alloys

A dual-phase nanostructured amorphous/crystalline model is an effective method to improve the mechanical properties of Mg alloys. However, the fundamental strengthening mechanism related to the interaction between basal/prismatic (BP) and amorphous phase in the dual-phase Mg alloys is still unclear. Here, the effects of the size and spacing of amorphous nanopillars on the mechanical properties and the BP interface migration behavior of the bicrystalline Mg alloys are investigated by the molecular dynamics simulation method. The results show that due to the attraction of amorphous nanopillar to interfacial dislocations, the introduction of amorphous nanopillar reduces the yield stress of the bicrystalline Mg alloys, and the yield stress decreases with the increase of the amorphous nanopillar radius. The results indicate that the amorphous nanopillar has an obvious blocking effect on the migration of the BP interface, and the larger the radius of amorphous nanopillars (or the smaller the spacing of amorphous nanopillars), the more obvious the strengthening effect. In addition, the migration mechanism of the BP interface in the bicrystalline Mg alloys is analyzed in detail.

Achieving exceptional improvement of yield strength in Mg–Zn–Ca alloy wire by nanoparticles induced by extreme plastic deformation

The size and distribution of second phase particles have an important influence on the mechanical properties of Mg alloys and further determine their application. In this study, extreme plastic deformation was employed to control the microstructure and tune the corresponding mechanical properties of Mg–Zn–Ca alloy. The uniformly dispersed nanoparticles (average diameter of ∼14.3 nm) could be successfully introduced into the Mg–Zn–Ca alloy wire after cold drawing with an area reduction of ∼99.8%, and the high yield strength of ∼285 MPa was obtained. When compared to the as-extruded alloy with yield strength of ∼171 MPa, the exceptional improvement in yield strength (∼114 MPa) for the Mg–Zn–Ca alloy wire is mainly attributed to the formation of nanoparticles. Moreover, the Mg wire also exhibited a good ductility of ∼11.8%. The results indicate that extreme plastic deformation can enable a refined microstructure to enhance the mechanical properties of Mg–Zn–Ca alloys.

Effect of rare earth element on amorphization and deformation behavior of crystalline/amorphous dual-phase Mg alloys

The crystalline/amorphous (C/A) dual-phase structure is a new design strategy to improve the mechanical properties of Mg alloys. Here, the effect of the content of rare-earth element Y on the deformation mechanism and mechanical behavior of the C/A Mg/(MgCu)100-xYx dual-phase Mg alloys under tensile loading is investigated by molecular dynamics simulation. The results show for the first time that the amorphous phase thickness of the alloys increases obviously after relaxation, which is mainly due to the existence of element Y in amorphous phase. And with the increase of the content of element Y, the thickness of amorphous phase increases. The results indicate that the diffusion of element Y from amorphous phase to amorphous-crystalline interface (ACI) promotes the migration of ACI towards crystalline phase (i.e., the amorphization of crystalline phase). The results further pointed out that the amorphization of Mg alloys depends on two factors: one is that the amorphous phase contains a certain concentration of element Y, and the other is the existence of ACI. The results show that there is a critical amorphous phase thickness of the dual-phase Mg alloys, that is, the critical content of Y element, which can make it achieve nearly perfect plasticity.

A Superior High-Strength Dilute Mg-Bi-Ca Extrusion Alloy with a Bimodal Microstructure

Improving the mechanical properties of Mg alloys is of great significance for their wide application. A micro-alloyed Mg-1.45Bi-0.79Ca alloy (in wt.%) exhibiting a high tensile yield strength of 394 ± 5 MPa and a moderate elongation of 6.6 ± 0.6% was fabricated by single pass extrusion. The superior high strength is mainly attributed to the synergy effects of ultra-fine dynamic recrystallized grains; numerous Mg2Ca, Mg3Bi2, and Mg2Bi2Ca nano-precipitates; residual dislocations; sub-grain boundaries; as well as strong &lt;10-10&gt; fibre texture in the extrusion direction.

Investigation on microstructure and mechanical properties of hot-rolled AZ31 Mg alloy with various cryogenic treatments

AZ31 Mg alloy sheet, prepared by a novel process combining hot rolling and various cryogenic treatments, has been investigated on its microstructure and mechanical properties. The results show that twins and the Al8Mn5 phase were introduced in the sample with rapid cooling and rapid heating and slow heating and slow cooling, which can significantly impede the movement of dislocations, while twins also can effectively coordinate deformation. Compared to the conventional hot rolling sample, the average grain size and texture strength of the cryogenic treatment samples were refined and increased by ∼24% and∼50%, respectively. The dislocation density of the coarse-grained region in the sample with slow heating and slow cooling is low, and the prismatic <a> and pyramid <c+a> slips were activated, which can improve the ductility of the alloy. In comparison to conventional hot rolling, the ultimate tensile strength and elongation of AZ31 Mg alloy after rapid cooling and rapid heating were increased by ∼15% and ∼37%, respectively, while the elongation after slow heating and slow cooling increased by ∼71%. The improvement of the mechanical properties of Mg alloy with cryogenic treatment is attributed to the synergistic effect of the refined grain, twins, residual dislocations, precipitates, texture and non-basal slip.

Multi-solute solid solution behavior and its effect on the properties of magnesium alloys

The low-density magnesium (Mg) alloys are attractive for the application in aerospace, transportation and other weight-saving-required fields. The mechanical properties and corrosion properties of Mg alloys are the key-property issues for the wide application. It is surprising to find that the solid solution of alloying elements in the α-Mg phase can have multi-effects on the properties of Mg alloys, e.g., solid solution strengthening, solid solution corrosion-resistance-enhancing, etc. Additionally, the alloy design theory of “solid solution strengthening and ductilizing” proposed by Pan and co-workers has attracted extensive attentions. It is promising that by selected proper multi-alloying-elements (with optimal ratio) solid solutioned in the α-Mg phase, the comprehensive properties of Mg alloys can be synergistically improved. In this work, the solid solution behavior of Mg alloys and the followed solid solution property-enhancing effects were reviewed. The mechanisms proposed recently by researchers for these solid solution property-enhancing behaviors were presented, and the related calculations and predictions were also described. It is shown the demonstrations of the fundamentals for the solid solution property-enhancing of Mg alloys, especially from the atomic inter-reaction aspects, still require elaborated characterization work and calculation work. Additionally, it could be expected that the multi-solute in Mg alloys can bring many possibilities, or, in another saying, “cocktail effects”. With understanding the multi-solute interaction behavior and the corresponded solid solution property-enhancing effects, the good balanced high-performance Mg alloys can be developed.

Microstructure, texture and mechanical properties of extruded AZ31 Mg alloy during small strain multi-directional forging with gradient cooling

A new small strain multi-directional forging (MDF) with gradient cooling was proposed to tailor the microstructure and improve the mechanical properties of Mg alloys. Using MDF with a cumulative strain of 2.7, a uniform fine-grained microstructure with an uncommon bimodal basal texture was achieved. Influenced by the Schmid factor, the twins in the< 10–10 > type grains rotated the basal poles toward the last forging direction (LFD), whereas the twins in the< 11–20 > type grains refined the microstructure. The dominant refinement mechanisms at high temperatures were twinning segmentation (TS) and discontinuous dynamic recrystallization (DDRX). It gradually became continuous dynamic recrystallization (CDRX) as the temperature was lowered. Twinning-induced recrystallization (TDRX) also occurred at 200 ℃. The plastic deformation and DRX mechanism affected the texture evolution of the grains. With a cumulative strain of less than 0.3, {10–12} twinning was dominant and responsible for the formation of the< 0001 > //LFD texture. As the cumulative strain increased to 0.9, multiple slips began to dominate the deformation, and a relatively stable< 10–12 > –< 11–24 > //LFD bimodal basal texture was formed. In contrast, the DRXs had little effect on texture types. The yield strengths were affected by the grain sizes and textures during MDF. The fluctuations of strength in the initial stage were mainly attributed to the texture change. When the texture was stabilized, the increases in strength were owing to grain refinement. The yield strengths can be accurately estimated by an improved Hall-Petch relation that includes the texture effect. • A newly small strain multi-directional forging with gradual cooling was proposed. • Fine-grained microstructure achieved undergoing sequential TS, DDRX, CDRX and TDRX. • Uncommon bimodal basal texture attributed to multiple slips activated by the MDF path. • Yield strengths and the anisotropy well estimated by an improved Hall-Petch relation.

Recent advances in micro-alloyed wrought magnesium alloys: Theory and design

Micro-alloying design of wrought magnesium (Mg) alloys is an important strategy to achieve high mechanical properties at a low cost. In the last two decades, significant progress has been made from both theory and experiment. In the present review, we try to summarize recent advances in micro-alloying design of wrought Mg alloys from both theoretical and pragmatic perspectives, and provide fundamental data required for establishing the relationship between chemical composition and mechanical properties of Mg alloys. We start with theoretical attempts for understanding the mechanical properties of Mg alloys at different scales, by involving first principle calculations, molecular dynamics, cellular automata, and crystal plasticity. Then, the role of alloying elements is discussed for a series of promising Mg alloys such as Mg-Al, Mg-Zn, Mg-RE (rare-earth element), Mg-Sn, and Mg-Ca families. Potential challenges in the micro-alloying design of Mg alloys are highlighted at the end. The review is expected to provide helpful guidance for the intelligent design of novel wrought Mg alloys and inspire more innovative ideas in this field.

Achieving enhanced high-temperature mechanical properties in Mg-Nd-Sm-Zn-Ca-Zr alloy by Ag addition

Mg alloys have been attracting particular interests in industrial manufacture. Nevertheless, the poor high-temperature mechanical properties of Mg alloys limit their further practical applications. Thus, as-cast Mg-2.5Nd-1.0Sm-0.4Zn-0.1Ca-0.5Zr-xAg (x = 0, 0.5, 1.0, 1.5, 2.0 wt%) alloys were designed and fabricated to overcome this shortcoming in this study. The influences of Ag addition on the microstructures and mechanical properties of Mg alloys were analyzed in detail. The results indicated that the microstructures of the alloy were composed of equiaxed α-Mg grains and β phase. The content of the β phase increased from 5.56% to 8.91% upon increasing the content of Ag from 0 wt% to 2.0 wt%, indicating that Ag can promote the formation of the β phase significantly. Moreover, the first-principles calculations supported that the formation enthalpy for the β phase was reduced with the doping of Ag resulting in increased stability of the β phase. Ag also enhanced the bulk modulus and ductility of the β phase. Meanwhile, the Young's modulus and elastic anisotropy of the β phase was diminished by Ag addition. The addition of Ag increased the strength and decreased the elongation of the as-cast alloys. The as-cast alloy with 2.0 wt% Ag addition achieved comprehensive mechanical properties. Furthermore, the as-cast alloy with 2.0 wt% Ag addition showed the least decrease in ultimate tensile strength with increasing temperature compared to the other alloys. The ultimate tensile strength of the as-cast alloy with 2.0 wt% Ag addition decreased from 196.0 MPa to 188.8 MPa as the temperature changed from 25 °C to 275 °C. The increase in strength and heat resistance of the alloys is mainly attributed to the increased β phase content and stability. Overall, this work developed a new heat resistant Mg-Nd-Sm-Zn-Ca-Zr-Ag alloy with excellent high-temperature mechanical properties. This suggests that it helps to improve the high-temperature mechanical properties and reliability of new aero engines and promote applications of lightweight engines.