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Magnesium is the most promising element as a bioresorbable material in bone repairing applications. Closed-cell Mg-2Zn-2Ca foam was fabricated through melt processing route by using economical biocompatible pure dolomite+MgCO3 as dual-blowing agent with favorable advantages of uniform pore structure, improved mechanical properties and good biocompatibility. In addition, residuals of blowing agent act as biocompatible particles during degradation. Mg-2Zn-2Ca foam was characterized for its physical, mechanical, in vitro degradation properties and microstructure characterization. Mg-2Zn-2Ca foams having relative density 0.41–0.45, average uniform pore size in the range of 0.25–0.75 mm revealed plastic compression strength up-to 50.1 MPa, plateau strength up to 43.2 MPa with 56.3% densification strain and 30 MJ/m3 of energy absorption per unit volume were obtained. Moreover, Mg foam exhibited adequate compressive behavior during in vitro degradation up to 4 weeks in simulated body fluid. Despite higher amount of hydrogen release in initial stage, Mg foam observed stable degradation mechanism after 2 weeks due to formation and deposition of degradation products on cellular surfaces. Based on the processing method and results obtained, Mg-2Zn-2Ca closed-cell foam satisfied the requirement of physical, mechanical and in vitro degradation properties compared to natural bone properties and recommended as cost effective, biocompatible and bone substitution mechanical implant material. [ABSTRACT FROM AUTHOR]

Coating is an effective approach to address the high corrosion rate of biodegradable Mg alloys, as their main challenge toward their extensive use. In this regard, it was tried to control the degradation process of an Mg–4Zn alloy by Ca addition, equal channel angular pressing (ECAP), and hydrothermal coating. The obtained results indicated that excellent grain refinement induced by Ca incorporation and ECAP simultaneously, improved both mechanical strength and corrosion resistance of the Mg-based substrate. The achieved grain refinement resulted in a thicker, more compact and integrated coating, where the ECAP-processed Mg–4Zn–0.5Ca alloy exhibited the best coating quality with no penetrative cracks. The ECAP-coated Mg–4Zn–0.5Ca alloy benefits from both the improved coating quality and superior substrate corrosion resistance, leading to a noticeable improvement in corrosion resistance. This emphasizes the positive role of Ca addition and ECAP process in promoting the mechanical properties and degradation behavior of Mg–4Zn substrate, as well as the quality of hydrothermally-synthesized coating.

Magnesium (Mg)-based implants are highly attractive for the orthopedic field and may replace titanium (Ti) as support for fracture healing. To determine the implant–bone interaction in different bony regions, we implanted Mg-based alloy ZX00 (Mg < 0.5 Zn < 0.5 Ca, in wt%) and Ti-screws into the distal epiphysis and distal metaphysis of sheep tibiae. The implant degradation and osseointegration were assessed in vivo and ex vivo after 4, 6 and 12 weeks, using a combination of clinical computed tomography, medium-resolution micro computed tomography (µCT) and high-resolution synchrotron radiation µCT (SRµCT). Implant volume loss, gas formation and bone growth were evaluated for both implantation sites and each bone region independently. Additionally, histological analysis of bone growth was performed on embedded hard-tissue samples. We demonstrate that in all cases, the degradation rate of ZX00-implants ranges between 0.23 and 0.75 mm/year. The highest degradation rates were found in the epiphysis. Bone-to-implant contact varied between the time points and bone types for both materials. Mostly, bone-volume-to-total-volume was higher around Ti-implants. However, we found an increased cortical thickness around the ZX00-screws when compared with the Ti-screws. Our results showed the suitability of ZX00-screws for implantation into the distal meta- and epiphysis. [ABSTRACT FROM AUTHOR]

For the purpose of developing biodegradable magnesium alloys with suitable properties for biomedical applications, Mg–Zn–Ca–Cu metallic glasses were prepared by copper mold injection methods. In the present work, the effect of Cu doping on mechanical properties, corrosion behavior, and glass‐forming ability of Mg66Zn30Ca4 alloy was studied. The experimental findings demonstrated that the incorporation of Cu decreases the corrosion resistance of alloys, but increases the microhardness and degradation rate slightly. However, the addition of a trace amount of Cu can make the samples have antibacterial properties. Therefore, Mg–Zn–Ca–Cu has great advantages in clinical implantation and is the potential implant material. [ABSTRACT FROM AUTHOR]

Biodegradable Mg–Zn–Ca-based metallic glasses (MGs) present improved strength and superior corrosion resistance, compared to crystalline Mg. In particular, in vivo and in vitro attempts reveal that biodegradable Mg–Zn–Ca-based MGs possess excellent biocompatibility, suggesting that they are ideal candidates for temporary implant materials. However, the limited size and severe brittleness prevent their widespread commercialization. In this review, we firstly summarize the microstructure characteristic and mechanical properties of Mg–Zn–Ca-based MGs. Then, we provide a comprehensive and systematic understanding of the recent progress of the biocorrosion and biocompatibility of Mg–Zn–Ca-based MGs. Last, but not least, the outlook towards the fabrication routes, composition design, structure design, and reinforcement approaches of Mg–Zn–Ca-based MGs are briefly proposed.

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The microstructure and mechanical properties of an as-extruded Mg-4.5Zn-1.1Ca (wt.%) alloy subjected to unidirectional rolling and cross-rolling were compared in the present study. The results indicated that rolling deformation refined the microstructure, dispersed second phases and modified the texture, which resulted in an improvement in the mechanical properties of the as-rolled alloys compared with those of the as-extruded alloy. The yield strength of the Mg-4.5Zn-1.1Ca (wt.%) alloy increased from 173 to 297 MPa after unidirectional rolling. The initial fragmented Ca2Mg6Zn3 phases were further refined after rolling deformation, which clearly restricted the grain growth and gave rise to a fine microstructure. It was also found that rolling deformation intensified the basal texture in comparison with the as-extruded alloy, which was related to particle pinning. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical properties and corrosion behaviors of as-cast ternary Mg-2Zn-xCa (x=0, 0.2, 0.4, 0.8) alloys have been investigated in this study. Results indicate that the microstructure of Mg-Zn-Ca alloys can be significantly refined with increasing Ca concentration. Moreover, the alloys with different contents of Ca exhibit the different phases formation behaviors, i.e. a-Mg + Ca2Mg6Zn3 phases for Mg-2Zn-0.2Ca and Mg-2Zn- 0.4Ca alloys, and a-Mg + Ca2Mg6Zn3 + Mg2Ca phases for Mg-2Zn-0.8Ca alloy, respectively. Among all the alloys, the maximum ultimate tensile strength and elongation (161 MPa and 9.1%) can be attained for the Mg-2Zn-0.2Ca alloy. Corrosion tests in Hanks' balanced salt solution indicated that Ca addition is detrimental to corrosion resistance of Mg-2Zn alloy. The relationship between as-cast microstructure and properties for different Ca-containing alloys is also discussed in detail. [ABSTRACT FROM AUTHOR]

Objectives: As promising alternative to current metallic biomaterials, the porous Mg scaffold with a 3‐D open‐pore framework has drawn much attention in recent years due to its suitable biodegradation, biocompatibility, and mechanical properties for human bones. This experiment's aim is to study the mechanical properties, biosafety, and osteogenesis of porous Mg‐Zn alloy. Methods: A porous Mg‐2Zn‐0.3Ca (wt%) alloy was successfully prepared by infiltration casting, and the size of NaCl particles was detected by a laser particle size analyzer. The microstructure of the Mg‐2Zn‐0.3Ca alloy was characterized by the stereoscopic microscope and Sirion Field emission scanning electron microscope. X‐ray computerized tomography scanning (x‐CT) was used to create the 3‐D image. The degradation rate was measured using the mass loss method and the pH values were determined together. The engineering stress–strain curve, compressive modulus, and yield strength were tested next. The bone marrow stromal cells (BMSC) were cultured in vitro. The CCK‐8 method was used to detect the proliferation of the BMSC. Alkaline phosphatase (ALP) and alizarin red staining were used to reflect the differentiation effects. After co‐culturing, cell growth on the material's surface was observed by scanning electron microscope (SEM). The cell adhesion was tested by confocal microscopy. Results: The obtained results showed that by using near‐spherical NaCl filling particles, the porous Mg alloy formed complete open‐cell foam with a very uniform size of pores in the range of 500–600 μm. Benefitting from the small size and uniform distribution of pores, the present porous alloy exhibited a very high porosity, up to 80%, and compressive yield strength up to 6.5 MPa. The degradation test showed that both the pH and the mass loss rate had similar change tendency, with a rapid rise in the early stage for 1–2 day's immersion and subsequently remaining smooth after 3 days. In vitro cytocompatibility trials demonstrated that in comparison with Ti, the porous alloy accelerated proliferation in 1, 3, 5, and 7 days (P < 0.001), and the osteogenic differentiation test showed that the ALP activity in the experimental group was significantly higher (P = 0.017) and has more osteogenesis nodules. Cell adhesion testing showed good osteoconductivity by more BMSC adhesion around the holes. The confocal microscopy results showed that cells in porous Mg‐based alloy had better cytoskeletal morphology and were larger in number than in titanium. Conclusions: These results indicated that this porous Mg‐based alloy fabricated by infiltration casting shows great mechanical properties and biocompatibilities, and it has potential as an ideal bone tissue engineering scaffold material for bone regeneration. [ABSTRACT FROM AUTHOR]

In this study, two biodegradable Mg-Zn-Ca alloys with alloy content of less than 1 wt % were strengthened via high pressure torsion (HPT). A subsequent heat treatment at temperatures of around 0.45 Tm led to an additional, sometimes even larger increase in both hardness and tensile strength. A hardness of more than 110 HV and tensile strength of more than 300 MPa were achieved in Mg-0.2Zn-0.5Ca by this procedure. Microstructural analyses were conducted by scanning and transmission electron microscopy (SEM and TEM, respectively) and atom probe tomography (APT) to reveal the origin of this strength increase. They indicated a grain size in the sub-micron range, Ca-rich precipitates, and segregation of the alloying elements at the grain boundaries after HPT-processing. While the grain size and segregation remained mostly unchanged during the heat treatment, the size and density of the precipitates increased slightly. However, estimates with an Orowan-type equation showed that precipitation hardening cannot account for the strength increase observed. Instead, the high concentration of vacancies after HPT-processing is thought to lead to the formation of vacancy agglomerates and dislocation loops in the basal plane, where they represent particularly strong obstacles to dislocation movement, thus, accounting for the considerable strength increase observed. This idea is substantiated by theoretical considerations and quenching experiments, which also show an increase in hardness when the same heat treatment is applied.

Mg-Zn-Ca amorphous alloys are considered as potential bone implants. A large number of works have focused on the alloys under free corrosion environment. However, the real service environment of bone implants is a kind of chemistry-mechanics interactive environment in which the materials not only suffer corrosion by body fluids but also bear applied force induced by body movement. In order to imitate the real service environment, surface morphologies and mechanical properties of Mg-Zn-Ca amorphous alloys were studied under different chemistry-mechanics interactive environments in this paper. It was found that cracks and Ca/Mg phosphates formed on the surface of amorphous alloys. The compressive strength of the alloys decreased seriously but could still reach an acceptable value to avoid material failure. Fan-shaped patterns found on all the samples implied that brittle fracture was the main fracture form. Moreover, vein-like patterns could still be found in some areas, showing a locally plastic deformation. This was the reason why the alloy could maintain a high compressive strength after severe and interactive treatments. The study could guide related works in the establishment of experimental environments in the future, which will facilitate a more accurate biomedical evaluation of bone implants.

Mg-Zn-Ca metallic glass (MG) is effective for degrading azo dyes; however, the related surface evolution and degradation mechanisms are little known. We comparatively investigated the initial surface corrosion morphologies of melt-spun Mg66Zn30Ca4 MG in deionized water and artificial seawater. It was found that the basic corrosion behavior of the MG was the same, except that the corrosion process was accelerated in seawater. The presence of NaCl obviously promotes the formation of nano-ZnO on the surface of ribbons, causing the rapid degradation of azo dyes due to the photocatalytic effect. The degradation efficiency when combined with 3.5 wt % NaCl was over 100 times higher than that without NaCl. This indicates that Mg-Zn-Ca MG ribbons are effective additives for the degradation of azo dyes in seawater. [ABSTRACT FROM AUTHOR]

The use of bioresorbable magnesium (Mg)-based elastic stable intramedullary nails (ESIN) is highly promising for the treatment of pediatric long-bone fractures. Being fully resorbable, a removal surgery is not required, preventing repeated physical and psychological stress for the child. Further, the osteoconductive properties of the material support fracture healing. Nowadays, ESIN are exclusively implanted in a non-transphyseal manner to prevent growth discrepancies, although transphyseal implantation would often be required to guarantee optimized fracture stabilization. Here, we investigated the influence of trans-epiphyseally implanted Mg-Zinc (Zn)-Calcium (Ca) ESIN on the proximal tibial physis of juvenile sheep over a period of three years, until skeletal maturity was reached. We used the two alloying systems ZX10 (Mg-1Zn-0.3Ca, in wt%) and ZX00 (Mg-0.3Zn-0.4Ca, in wt%) for this study. To elaborate potential growth disturbances such as leg-length differences and axis deviations we used a combination of in vivo clinical computed tomography (cCT) and ex vivo micro CT (μCT), and also performed histology studies on the extracted bones to obtain information on the related tissue. Because there is a lack of long-term data regarding the degradation performance of magnesium-based implants, we used cCT and μCT data to evaluate the implant volume, gas volume and degradation rate of both alloying systems over a period of 148 weeks. We show that transepiphyseal implantation of Mg-Zn-Ca ESIN has no negative influence on the longitudinal bone growth in juvenile sheep, and that there is no axis deviation observed in all cases. We also illustrate that 95 % of the ESIN degraded over nearly three years, converging the time point of full resorption. We thus conclude that both, ZX10 and ZX00, constitute promising implant materials for the ESIN technique., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Annelie-Martina Weinberg reports a relationship with Bioretec YO that includes: consulting or advisory., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Mg‒Zn‒Ca metallic glasses are regarded as promising biodegradable materials. Previous studies on this alloy system have mostly focused on the composition regions with a large critical size (Dc) for the formation of metallic glasses, while this paper investigates the composition regions with a small Dc, which has been overlooked by researchers for a long time. The effects of the addition of Ag, Nd, and Yb elements on the microstructure and mechanical properties of Mg‒Zn‒Ca metallic glasses were studied. It was found that the Mg‒Zn‒Ca metallic glass exhibits a single and uniform amorphous structure with a compressive strength of 590 MPa. After the addition of a small amount of Ag into the alloy, the amorphous matrix is retained and new precipitate phases that lead to the decrease of the compressive strength are formed. The addition of the rare earth elements Nd and Yb changes the microstructure from a single amorphous matrix to a large number of quasicrystal phases, which results in an increase in compressive strength. The compressive strength of the Mg‒Zn‒Ca‒Yb alloy increases to 606.2 MPa due to the formation of multi-layered swirling solidified structure and a large number of small quasicrystals with high microhardness. Moreover, this study can be considered as a useful supplement to the existing studies on the Mg‒Zn‒Ca alloy system; it also provides new ideas for designing the microstructure and spatial structure of quasicrystal containing alloys with high performances.

Paduan magnesium banyak diaplikasikan pada dunia otomotif mobil atau motor dan mesin pesawat terbang. Haq al ini dikarenakan berat dari magnesium sendiri yang sangat ringan dan memiliki kekuatan tinggi. Serta paduan magnesium memiliki konduktifitas termal yang baik, modulus elastisitas yang tinggi dan memiliki sifat mekanik yang baik. Magnesium dalam aplikasi teknik biasanya di padukan dengan unsur seperti Al, Ag, Mn, Zn, Si, Zr dan RE (rare element). Pada penelitian ini telah dilakukan proses pemaduan sistem Mg-Zn-Ca dengan menggunakan variabel komposisi Ca yaitu 0 wt.%; 0,5 wt.%; 1,5 wt.%; dan 3 wt.%Ca terhadap paduan awal Mg-6Zn. Hasil penelitian menunjukkan struktur mikro yang terbentuk adalah αMg, MgZn, Mg2Ca, dan Mg6Zn3Ca2. Penambahan 3 wt.% Ca menghasilkan paduan paling stabil pada temperatur tinggi. Adanya fasa Mg6Zn3Ca2menaikkan nilai kekerasan menjadi 74,05 BHN

New Mg-3Zn-2Ca magnesium alloy was prepared using different processing techniques: gravity casting as well as squeeze casting in liquid and semisolid states. Materials were further thermally treated; thermal treatment of the gravity cast alloy was additionally combined with the equal channel angular pressing (ECAP). Alloy processed by the squeeze casting in liquid as well as in semisolid state exhibit improved plasticity; the ECAP processing positively influenced both the tensile and compressive characteristics of the alloy. Applied heat treatment influenced the distribution and chemical composition of present intermetallic phases. Influence of particular processing techniques, heat treatment, and intermetallic phase distribution is thoroughly discussed in relation to mechanical behavior of presented alloys. [ABSTRACT FROM AUTHOR]

Rod samples of Mg60Zn35Ca5 bulk metallic glass composites (BMGCs) dispersed with Ti particles have been successfully fabricated via injection casting. The glass forming ability (GFA) and the mechanical properties of these Mg-based BMGCs have been systematically investigated as a function of the volume fraction (Vf) of Ti particles. The results showed that the compressive ductility increased with Vf. The mechanical performance of these BMGCs, with up to 5.4% compressive failure strain and 1187 MPa fracture strength at room temperature, can be obtained for the Mg-based BMGCs with 50 vol % Ti particles, suggesting that these dispersed Ti particles can absorb the energy of the crack propagations and can induce branches of the primary shear band into multiple secondary shear bands. It follows that further propagation of the shear band is blocked, enhancing the overall plasticity. [ABSTRACT FROM AUTHOR]

The bio-corrosion behaviour of Mg–3Zn–0.3Ca (wt.%) alloy in simulated body fluid (SBF) at 37 °C has been investigated using immersion testing and electrochemical measurements. Heat treatment has been used to alter the grain size and secondary phase volume fraction; the effects of these on the bio-corrosion behaviour of the alloy were then determined. The as-cast sample has the highest bio-corrosion rate due to micro-galvanic corrosion between the eutectic product (Mg + Ca 2 Mg 6 Zn 3 ) and the surrounding magnesium matrix. The bio-corrosion resistance of the alloy can be improved by heat treatment. The volume fraction of secondary phases and grain size are both key factors controlling the bio-corrosion rate of the alloy. The bio-corrosion rate increases with volume fraction of secondary phase. When this is lower than 0.8%, the dependence of bio-corrosion rate becomes noticeable: large grains corrode more quickly. [ABSTRACT FROM AUTHOR]

New Mg-3Zn-2Ca magnesium alloy was prepared using different processing techniques: gravity casting as well as squeeze casting in liquid and semisolid states. Materials were further thermally treated; thermal treatment of the gravity cast alloy was additionally combined with the equal channel angular pressing (ECAP). Alloy processed by the squeeze casting in liquid as well as in semisolid state exhibit improved plasticity; the ECAP processing positively influenced both the tensile and compressive characteristics of the alloy. Applied heat treatment influenced the distribution and chemical composition of present intermetallic phases. Influence of particular processing techniques, heat treatment, and intermetallic phase distribution is thoroughly discussed in relation to mechanical behavior of presented alloys.

Abstract: The dynamic properties and atomic configuration of Mg, Mg–Zn, Mg–Zn–Ca and Mg–Zn–Ca–Cu liquid and solid systems were comprehensively studied using ab initio molecular dynamics calculation. The viscosities of an Mg–Zn–Ca alloy were measured from 700K to 960K. It was found that Zn and Ca in Mg liquid induce remarkable slowing down of atoms, but Cu acted as a stimulus to the diffusion. Icosahedral short-range orders are most dominant in Mg–Zn–Ca alloys in view of the existence of a majority of 1551 type of bond pairs, 〈0,0,12,0〉 type of Voronoi polyhedra. Icosahedral medium-range orders can be formed in Mg–Zn–Ca alloys by the perfect icosahedra via the linkage of vertex-, edge-, face- and intercross-shared atoms. It is suggested that the high glass forming ability of Mg–Zn–Ca alloys is essentially related to the sluggish mobility and strong icosahedral short- and medium-range ordering in the undercooled liquid. [Copyright &y& Elsevier]

Highlights: [•] Mg–Zn–Ca metallic glass powders were synthesized by gas-atomization. [•] The phase structure of powders was affected by the composition and the size. [•] Degradation capacity of powders is determined by phase constituents and Mg content. [•] Nano-whiskers are distributed loosely on the reacted surface of the glassy powder. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, corrosion resistance of the Mg–4.0Zn–0.2Ca alloy was modified by micro-arc oxidation (MAO) process. The microstructure and phase constituents of MAO layer were characterized by SEM, XRD and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of MAO treated Mg–4.0Zn–0.2Ca alloy in the simulated body fluid were characterized by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The microstructure results indicated that a kind of ceramic film was composed by MgO and MgF2 was formed on the surface of Mg–4.0Zn–0.2Ca alloy after MAO treatment. The electrochemical test reveals that the corrosion resistance of MAO treated samples increase 1 order of magnitude. The mechanical intensity test showed that the MAO treated samples has suitable mechanical properties. [Copyright &y& Elsevier]

Magnesium (Mg)-based implants are highly attractive for the orthopedic field and may replace titanium (Ti) as support for fracture healing. To determine the implant-bone interaction in different bony regions, we implanted Mg-based alloy ZX00 (Mg < 0.5 Zn < 0.5 Ca, in wt%) and Ti-screws into the distal epiphysis and distal metaphysis of sheep tibiae. The implant degradation and osseointegration were assessed in vivo and ex vivo after 4, 6 and 12 weeks, using a combination of clinical computed tomography, medium-resolution micro computed tomography (µCT) and high-resolution synchrotron radiation µCT (SRµCT). Implant volume loss, gas formation and bone growth were evaluated for both implantation sites and each bone region independently. Additionally, histological analysis of bone growth was performed on embedded hard-tissue samples. We demonstrate that in all cases, the degradation rate of ZX00-implants ranges between 0.23 and 0.75 mm/year. The highest degradation rates were found in the epiphysis. Bone-to-implant contact varied between the time points and bone types for both materials. Mostly, bone-volume-to-total-volume was higher around Ti-implants. However, we found an increased cortical thickness around the ZX00-screws when compared with the Ti-screws. Our results showed the suitability of ZX00-screws for implantation into the distal meta- and epiphysis., (© The Author(s) 2022. Published by Oxford University Press.)

Abstract: SiCp/Mg–Zn–Ca composite fabricated by stir casting was extruded at three different temperatures. Firstly, hot extrusion significantly improved particle distribution and refined the grains of the matrix. Even, nano-grains were observed in the composite extruded at 250°C. Secondly, extrusion evidently refined the size of the second phases, but also changed the distribution of the second phases. Extrusion temperatures obviously affected the size and distribution of the second phases. Thirdly, the interface between SiCp and matrix was also modified by hot extrusion. Finally, all as-extruded composites possessed good mechanical properties. Below 150°C, the UTS was very high in the extruded composites, but their strengths decreased sharply above 150°C. [Copyright &y& Elsevier]

Abstract: A Mg phosphate coating was prepared on home-developed Mg–Zn–Ca alloy to improve its anticorrosion performance in simulated body fluid (SBF, Kokubo solution). The coating was prepared by micro-arc oxidation (MAO) method at the working voltage of 120–140V. Evident improvement of anticorrosion was obtained even through the surface was porous. To further diminish the contact with SBF, a TiO2 layer was coated on the porous MAO layer by sol–gel dip coating followed by an annealing treatment. The coatings were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The electrochemical performance of the MAO and TiO2/MAO coated alloys was evaluated by anodic polarization measurements. The pores on Mg phosphate layer provided accommodation sites for the subsequent TiO2 sol–gel coating which sealed the pores and hence significantly enhanced the anticorrosion while single MAO coating only improve anticorrosion within a limited range. The present result indicates that fabrication of composite coatings is a significant strategy to improve the corrosion resistance of Mg–Zn–Ca alloy and other alloys, thus enhancing the potential of using Mg alloys as bio-implants. [Copyright &y& Elsevier]

Biodegradable Mg-Zn-Ca-based metallic glasses (MGs) present improved strength and superior corrosion resistance, compared to crystalline Mg. In particular, in vivo and in vitro attempts reveal that biodegradable Mg-Zn-Ca-based MGs possess excellent biocompatibility, suggesting that they are ideal candidates for temporary implant materials. However, the limited size and severe brittleness prevent their widespread commercialization. In this review, we firstly summarize the microstructure characteristic and mechanical properties of Mg-Zn-Ca-based MGs. Then, we provide a comprehensive and systematic understanding of the recent progress of the biocorrosion and biocompatibility of Mg-Zn-Ca-based MGs. Last, but not least, the outlook towards the fabrication routes, composition design, structure design, and reinforcement approaches of Mg-Zn-Ca-based MGs are briefly proposed.

Mg–Zn–Ca alloys are representative Mg alloys with high formability at room temperature. Their high formability is thought to be related to slip, twinning, and recrystallization of the alloys, but the detailed mechanisms have not yet been clarified. To enable atomistic simulations for investigating those behaviors, an interatomic potential for the Mg–Zn–Ca ternary system was developed. The development was based on the second nearest-neighbor modified embedded-atom method formalism, combining previously developed Mg–Zn and Mg–Ca potentials with the newly developed Zn–Ca binary potential. The Zn–Ca and Mg–Zn–Ca potentials reproduce structural, elastic, and thermodynamic properties of compounds and solution phases of relevant alloy systems in reasonable agreement with experimental data, first-principles and CALPHAD calculations. The applicability of the developed potentials is demonstrated through calculations of the effects of Zn and Ca solutes on the generalized stacking fault energy for various slip systems, segregation energy on twin boundaries, and volumetric misfit strain. • 2NN MEAM potentials for Mg–Zn–Ca ternary and Zn–Ca binary systems are developed. • The potentials describe various properties of the Mg–Zn–Ca and Zn–Ca alloys well. • The potentials can be utilized to atom-scale investigations of Mg–Zn–Ca alloys. [ABSTRACT FROM AUTHOR]

In this study, two biodegradable Mg-Zn-Ca alloys with alloy content of less than 1 wt % were strengthened via high pressure torsion (HPT). A subsequent heat treatment at temperatures of around 0.45 Tm led to an additional, sometimes even larger increase in both hardness and tensile strength. A hardness of more than 110 HV and tensile strength of more than 300 MPa were achieved in Mg-0.2Zn-0.5Ca by this procedure. Microstructural analyses were conducted by scanning and transmission electron microscopy (SEM and TEM, respectively) and atom probe tomography (APT) to reveal the origin of this strength increase. They indicated a grain size in the sub-micron range, Ca-rich precipitates, and segregation of the alloying elements at the grain boundaries after HPT-processing. While the grain size and segregation remained mostly unchanged during the heat treatment, the size and density of the precipitates increased slightly. However, estimates with an Orowan-type equation showed that precipitation hardening cannot account for the strength increase observed. Instead, the high concentration of vacancies after HPT-processing is thought to lead to the formation of vacancy agglomerates and dislocation loops in the basal plane, where they represent particularly strong obstacles to dislocation movement, thus, accounting for the considerable strength increase observed. This idea is substantiated by theoretical considerations and quenching experiments, which also show an increase in hardness when the same heat treatment is applied. [ABSTRACT FROM AUTHOR]

Mg-Zn-Ca amorphous alloys are considered as potential bone implants. A large number of works have focused on the alloys under free corrosion environment. However, the real service environment of bone implants is a kind of chemistry-mechanics interactive environment in which the materials not only suffer corrosion by body fluids but also bear applied force induced by body movement. In order to imitate the real service environment, surface morphologies and mechanical properties of Mg-Zn-Ca amorphous alloys were studied under different chemistry-mechanics interactive environments in this paper. It was found that cracks and Ca/Mg phosphates formed on the surface of amorphous alloys. The compressive strength of the alloys decreased seriously but could still reach an acceptable value to avoid material failure. Fan-shaped patterns found on all the samples implied that brittle fracture was the main fracture form. Moreover, vein-like patterns could still be found in some areas, showing a locally plastic deformation. This was the reason why the alloy could maintain a high compressive strength after severe and interactive treatments. The study could guide related works in the establishment of experimental environments in the future, which will facilitate a more accurate biomedical evaluation of bone implants. [ABSTRACT FROM AUTHOR]

Mg‒Zn‒Ca metallic glasses are regarded as promising biodegradable materials. Previous studies on this alloy system have mostly focused on the composition regions with a large critical size (Dc) for the formation of metallic glasses, while this paper investigates the composition regions with a small Dc, which has been overlooked by researchers for a long time. The effects of the addition of Ag, Nd, and Yb elements on the microstructure and mechanical properties of Mg‒Zn‒Ca metallic glasses were studied. It was found that the Mg‒Zn‒Ca metallic glass exhibits a single and uniform amorphous structure with a compressive strength of 590 MPa. After the addition of a small amount of Ag into the alloy, the amorphous matrix is retained and new precipitate phases that lead to the decrease of the compressive strength are formed. The addition of the rare earth elements Nd and Yb changes the microstructure from a single amorphous matrix to a large number of quasicrystal phases, which results in an increase in compressive strength. The compressive strength of the Mg‒Zn‒Ca‒Yb alloy increases to 606.2 MPa due to the formation of multi-layered swirling solidified structure and a large number of small quasicrystals with high microhardness. Moreover, this study can be considered as a useful supplement to the existing studies on the Mg‒Zn‒Ca alloy system; it also provides new ideas for designing the microstructure and spatial structure of quasicrystal containing alloys with high performances. [ABSTRACT FROM AUTHOR]

New Mg-3Zn-2Ca magnesium alloy was prepared using different processing techniques: gravity casting as well as squeeze casting in liquid and semisolid states. Materials were further thermally treated; thermal treatment of the gravity cast alloy was additionally combined with the equal channel angular pressing (ECAP). Alloy processed by the squeeze casting in liquid as well as in semisolid state exhibit improved plasticity; the ECAP processing positively influenced both the tensile and compressive characteristics of the alloy. Applied heat treatment influenced the distribution and chemical composition of present intermetallic phases. Influence of particular processing techniques, heat treatment, and intermetallic phase distribution is thoroughly discussed in relation to mechanical behavior of presented alloys.