Mg-Zn Binary Alloys Research Articles

Effect of Indium on the Properties of Mg-Zn-Based Alloys

In this study, indium was added to the binary Mg-Zn alloy to prepare an ultrafine-grained ternary Mg-Zn-In alloy with enhanced mechanical and corrosion properties. The bulk Mg-Zn-In alloy was synthesized through a combination of mechanical alloying and powder metallurgy techniques. The SPEX 8000 mixer mill was used to carry out the process under an argon atmosphere. The mixed powders were mechanically alloyed for 24 h. The mixture was uniaxially pressed at a compacting pressure of 600 MPa. The green compacts were sintered under a protective argon atmosphere at 300 °C for 1 h. The evolution of the microstructural, mechanical, and corrosion properties of Mg-based alloys was studied. X-ray diffraction and scanning electron microscopy were used to analyze the phase and microstructure. The changes in hardness and corrosion properties were also measured. Compared to binary Mg-Zn alloy samples modified with In, the samples exhibited a higher microhardness, which can be related to structure refinement and phase distribution. Based on the results of electrochemical testing, it was observed that the modified samples exhibited an improved level of corrosion resistance compared to the Mg-Zn binary alloy.

Development of High Strength and High Thermal Conductivity Semi-Solid Magnesium Alloy by Thixomolding Process

This paper investigates the influence of Cu addition on the microstructure, mechanical properties, and thermal conductivity of a semi-solid Mg-10Zn alloy produced by Thixomolding process. Microstructure of the Mg-10Zn alloy consists of α-Mg matrix and Mg2Zn second phase. The formation of Cu3Zn phase was found after the addition of Cu particles. Besides, the volume fraction of solid phase decreased in the Mg-Zn/Cu alloy compared with that of binary Mg-Zn alloy. The yield strength of the alloy was enhanced from 157MPa to 188MPa after Cu addition at the sacrifice of a small amount of ductility. Thermal conductivity, on the other hand, were kept the same level of 115-117 (W/m·K) in the Mg-10Zn alloy and Mg-10Zn/Cu alloy. This work demonstrates the potential for developing Mg alloys with high strength and high thermal conductivity via proper alloy design using Thixomolding process.

Nucleation of recrystallization in magnesium alloy grains of varied orientation and the impacts on texture evolution

Selection of appropriate thermomechanical processing parameters is crucial for control of the crystallographic texture and grain size distribution in wrought magnesium alloys, which in turn dictate their mechanical properties. In this work, the recrystallization behavior of binary Mg-Zn alloys are examined after warm rolling as a function of alloy content and heat treatment temperature. The Avrami exponent increased with increasing heat treatment temperature up to the MgZn solvus, while the strength of the recrystallization texture decreased. Neither the Avrami exponent nor the qualitative trends in texture evolution were sensitive to the Zn alloying content in the examined range. EBSD and transmission electron microscopy observations revealed that the changes in texture and recrystallization kinetics could be attributed to differences in the nucleation behavior of basal and off-basal orientations.

Deformation induced solute segregation and G.P. zone formation in Mg-Al and Mg-Zn binary alloys

A dispersion of Guinier Preston (G.P.) zones yields attractive mechanical properties in wrought magnesium alloys. However, the precipitation of G.P. zones has been reported in a limited number of Mg alloys. Here, we report deformation-induced G.P. zone precipitation in Mg-9Al and Mg-5 Zn (wt.%) alloys following equal channel angular extrusion at 150 °C. While the extrusion leads to the formation of a bimodal grain structure consisting of unrecrystallized and recrystallized regions, atom probe tomography reveals a high number density of G.P. zones across both regions. Furthermore, hybrid molecular dynamics/Monte Carlo simulations suggest that the attraction of Al and Zn solute atoms to vacancy clusters formed from excess vacancies during extrusion could be the major driving force for the G.P. zone formation. This combination of experiments and computations demonstrates that strategic control of atomic-scale defects can generate novel, far from equilibrium, microstructures, thereby providing an innovative approach to strengthening severely deformed Mg alloys.

Printability, mechanical and degradation properties of Mg-(x)Zn elemental powder mixes processed by laser powder bed fusion

• Printability of binary Mg-Zn alloys with 0, 0.5, 1, 2, 5 and 8 wt% were investigated by laser powder bed fusion. • Density parameter maps for varying laser power and scan speed were recorded for each alloy composition. • Mg0.5 Zn and Mg1Zn possessed the highest density results. • UTS of Mg1Zn was 126 MPa at a strain at failure of 5.7% and Mg0.5 Zn averaged 113 MPa at 5.4%, but showed better reproducibility. • Mg0.5 Zn and Mg1Zn possessed similar degradation behavior but were inferior to a LPBFed WE43 reference.

Calculation of Thermodynamic Properties of Mg-Zn-Al Alloy

The thermodynamic properties of Mg, Zn, Al binary alloys and ternary alloys were calculated by Miedema model and Toop model, and magnesium was selected as the asymmetric component. The results show that the mixing enthalpy, excess entropy and excess Gibbs free energy of Al-Zn binary alloy are all greater than zero. The thermodynamic values of Mg-Al and Mg-Zn binary alloys are relatively similar, and both are less than zero. Within the range of composition variation, the excess Gibbs free energy of Mg-Zn-Al ternary alloy is basically negative. In the Mg-poor and Mg-rich regions, the thermodynamic value of the alloy changes greatly. Excess Gibbs free energy and mixing enthalpy of magnesium-zinc-aluminum alloy can be reduced by adding zinc and aluminum.

Influences of Zinc Content and Solution Heat Treatment on Microstructure and Corrosion Behavior of Mg-Zn Binary Alloys

The influences of Zn content and heat treatment on microstructure and corrosion behavior of Mg-xZn (x = 1 wt%, 3 wt%, 5 wt%, and 7 wt%) alloys were studied. (α-Mg+MgZn) eutectic cells and Zn-segregated regions were formed in the as-cast alloys. The Zn-rich phases acted as microcathodes in galvanic corrosion. Volume fraction of the Zn-rich phases increased with Zn content of the as-cast alloys, leading to a decrease in corrosion resistance. The corrosion rate of the as-cast alloys increased four times with an increase of the volume fraction of eutectic cell from 0.07 vol% of Mg-1Zn alloy to 2.18 vol% of Mg-5Zn alloy. The corrosion rate of Mg-7Zn alloy with 2.87 vol% eutectic cells was two times higher than that of Mg-5Zn alloy. The Zn-rich phases dissolved by the T4 treatment and only the T4-treated Mg-7Zn alloy obviously showed eutectic cells of 1.73 vol%. The polarization resistance (Rp) of the T4-treated Mg-1, 3, and 5Zn alloys was 2 to 10 times higher than that of the as-cast alloys. The T4-treated Mg-7Zn showed similar Rp to the as-cast Mg-5Zn alloy. Consequently, the volume fraction of Zn-rich phases dominated the corrosion resistance of Mg-xZn alloys.

Processing characterization of binary Mg-Zn alloys fabricated by a new powder consolidation combined severe plastic deformation method

Abstract In this paper, a new powder consolidation combined severe plastic deformation method including integrated cyclic extrusion compression (CEC), equal channel angular pressing (ECAP) and conventional extrusion was presented for processing of binary Mg-Zn alloys for biomedical applications. This research shall strive to analyze the microstructure, mechanical and corrosion properties of binary magnesium-zinc alloys with 3, 7 and then 15 wt%Zn. Upon mixing Mg and Zn powders with a variety of Zn contents, the proposed combined method was used to consolidate the mixture of powders. All alloys were thoroughly examined and demonstrated areas of partial recrystallization and high deformation. The results indicate that adding zinc to magnesium improves the mechanical properties, but these properties are deteriorated with the zinc content of over 3 wt%. The corrosion behavior of the alloy in a bio-environment was examined by immersion test, mass loss and polarization tests in Hank’s solution. The results indicate that Mg-3Zn exhibits the best corrosion resistance and the corrosion rate increases when the Zn content is more than 3 wt%. Furthermore, the samples produced through the proposed method in this work indicates better corrosion resistance in comparison with the cast and extruded pure Mg.

Influence of heat treatment on microstructure and electrochemical behaviors of Mg-Zn binary alloys prepared by gas-phase alloying technique

Mg-Zn binary alloys fabricated by the gas-phase alloying technique under vacuum condition were investigated in the state of initial state and after heat treatment for the microstructure and electrochemical behaviors. Different from the traditional Mg-Zn alloys preparation methods, alloys prepared by gas-phase alloying have a large number of intermetallic compounds, such as MgZn, Mg7Zn3 and MgZn2. After solution treatment, the boundary of the eutectic disappeared and the size of α-Mg increased from 100 μm to 150 μm. At the same time, the value of the resistance of charge transfer increased, which indicates that the resistance of the charge transfer and the corrosion resistance of the alloys increased. After artificial aging treatment, the distribution of α-Mg was more uniform and its size was reduced to about 50 μm, and there was new eutectic structure formed. The newly formed eutectic structure forms galvanic cells with the alloy matrix, which makes the corrosion resistance of the alloy weaken.

The Effect of Zn in as-Cast Mg-Zn Alloys for Biodegradable Materials

This research presents the analysis of microstructure, mechanical, and corrosion behavior of three Mg-Zn binary alloys, Mg-1Zn, Mg-3Zn, and Mg-5Zn. The result of metallography for as-Cast Mg-Zn alloys with different Zn content shows that the presence of Zn will cause grain refinement effect to the microstructure of Mg-Zn alloys and allows the formation of γ phase of Mg-Zn precipitation along the grain boundaries. The addition of Zn also significantly increases the mechanical properties of magnesium alloys corresponding to fine grain strengthening and second phase strengthening effect. Immersion test in Ringer’s solution show that the addition of Zn in magnesium alloys reduce its corrosion rate by improving magnesium alloys corrosion potential.

Selective laser melting of Mg-Zn binary alloys: Effects of Zn content on densification behavior, microstructure, and mechanical property

Mg-Zn binary alloys with seven distinctive compositions (Zn (wt.%) = 1, 2, 4, 6, 8, 10 and 12) were prepared using a selective laser melting (SLM) additive manufacturing technology. Densification behaviors and microstructure of the SLM-processed alloys were analyzed using quantitative metallography analysis, XRD, SEM, and EDS. The mechanical property characterizations were carried out through microhardness and uniaxial tensile tests. The results showed that the increase of Zn content had a significantly deteriorating effect on the densification response of the SLM-processed Mg-Zn alloys. At 1 wt% Zn content, near full-dense products could be obtained. At 2–10 wt% Zn contents, SLM-processed alloys suffered from solidification cracking and the crack density showed an approximate “Λ-shaped” variation trend with the increase of Zn content. At 12 wt% Zn content, solidification cracks were eliminated but lots of micro-pores formed within the SLM sample. All the SLM samples exhibited a duplex microstructure composed of α-Mg matrix and Mg7Zn3 eutectic phase. With the increase of Zn content, the quantity of Mg7Zn3 increased continuously whilst its morphology gradually transformed from granular shape to nearly reticular structure. The hardness and tensile tests showed that only the Mg-1Zn sample has comparable mechanical properties with the as-cast counterpart. At higher Zn contents, mechanical properties of the SLM-processed alloys became significantly degraded, mainly because of the deterioration of the densification degree.

Study on the Mg-Zn binary alloys fabricated by gas-phase alloying

By adjusting the evaporation temperatures and changing the Mg/Zn atomic ratios (in the range of 0.5 to 4), various Mg-Zn binary alloys were fabricated usofing a novel technique named as gas-phase alloying. The theoretical calculation by the formula of saturated vapor pressure is to determine the evaporation temperature, which is 900-1200K for Mg and 700-1000K for Zn. The specimens were subjected to SEM, EDS, and Brinell hardness examinations. The results obtained show that, regardless of atomic ratios, microstructures include Mg7Zn3 particles and α-Mg matrix, the former is uniformly distributed into the latter. However, with increasing Mg/Zn atomic ratios, the microstructural transformation occurs from columnar precipitation to granular one.

Influence of alloying element Zn on the microstructural, mechanical and corrosion properties of binary Mg-Zn alloys after severe plastic deformation

This work presents an analysis of the microstructural, mechanical and corrosion properties of two binary Mg-Zn alloys. Mg-6 wt%Zn and Mg-12 wt%Zn cast alloys were subjected to annealing followed by quenching and processed via equal channel angular pressing with applied back-pressure (ECAP-BP). After ECAP-BP, both alloys were thoroughly examined and showed partially recrystallized and highly deformed areas. High-angle annular dark-field imaging revealed a difference in Zn content across the α-Mg matrix of the Mg-12 wt%Zn after ECAP-BP due to the growth of MgZn2 nanoparticles. Electron energy-loss spectroscopy (EELS) was carried out to qualify an average Zn content in these areas, and a variation in Zn content up to 2at.% was found. Compression tests revealed mechanical anisotropy and a significant increase in the strength of both alloys after ECAP-BP. The yield strength, σ02, was in the range from 269 to 385MPa depending on the composition and compression axis. The initial state alloys showed yield strengths, σ02, of only 75–150MPa but improved ductility. The corrosion rates of the Mg-Zn alloys in the initial state, evaluated using a hydrogen evolution method in NaCl solution, were higher for Mg-12 wt%Zn. The corrosion rates of both alloys after ECAP-BP were higher than those of the initial state. Light microscopy observations did not reveal any preference for corrosion propagation, including transcrystalline, intercrystalline or interphase corrosion, in any of the materials.

Effects of Cu addition on microstructure and mechanical properties of as-cast Mg-6Zn magnesium alloy

The application of Mg-Zn binary alloys is restricted due to their developed dendritic microstructure and poor mechanical properties. In this study, an alloying method was used to improve the mechanical properties of Mg-Zn alloy. The Mg-6Zn magnesium alloys microalloyed with varying Cu content (0, 0.8, 1.5, 2.0 and 2.5wt.%) were fabricated by permanent mould casting, and the effects of Cu content on the microstructure and mechanical properties of as-cast Mg-6Zn alloys were studied using OM, SEM, XRD and tensile tests at room temperature. The obtained results show that the addition of Cu not only can refine the grains effectively, but also can modify the eutectic morphology and improve the mechanical properties of the alloys. The main phases of the studied alloys include α-Mg, MgZn2, Mg2Cu and CuMgZn. When the content of Cu exceeds 0.8wt.%, Mg2Cu phase appears. Meanwhile, the eutectic morphology is modified into dendritic shape or lamellar structure, which has an adverse effect on the tensile properties. Furthermore, among the investigated alloys, the alloy containing 0.8% Cu shows an optimal ultimate tensile strength of 196 MPa, while the alloy with 1.5wt.% Cu obtains an excellent elongation of 7.22%. The experimental alloys under different Cu contents show distinguishing fracture behaviors: the fracture of the alloy with 0.8wt.% Cu reveals a mixed mode of inter-granular and quasi-cleavage, while in other investigated alloys, the fracture behaviors are dominated by cleavage fracture.

Correlation between local structures and glass forming ability of liquid MgxZn1 − x alloys

The liquid structures of a series of Mg-Zn alloys have been investigated in the present work by means of ab initio molecular dynamic simulation. Strong chemical short-range orders are observed for the eutectic alloy Mg70Zn30, i.e. the best glass former of Mg-Zn binary alloys, which is consistent with the experiment results. The pair analysis indicates the extraordinary abundance of icosahedral clusters in this eutectic liquid alloy. Furthermore, the self-diffusion coefficients of Mg and Zn reach minimum for the Mg70Zn30 alloy. The entire results offer an interpretation for the better glass forming ability of the Mg70Zn30 alloy.

Synthesis of Biodegradable Mg-Zn Alloy by Mechanical Alloying: Effect of Milling Time

Magnesium (Mg) is one such promising light weight metal, which is currently utilized for bio-engineering applications. Mg possesses a number of attractive characteristics that make Mg-based materials potential candidates to serve as implants for load-bearing applications in the medical industry due to its good biocompatibility and biodegradability. However, Mg and its alloys are susceptible to suffer attack in chloride containing solutions, e.g. the human body fluid or blood plasma. Thus, alloying with other metal elements is the most effective tool to improve mechanical properties and corrosion resistance of Mg. In this current work, binary Mg-Zn alloy was produced using mechanical alloying (MA) followed by compaction and sintering. The aim of this work was to study the effect of milling time on binary magnesium-zinc (Mg-Zn) alloy synthesized by mechanical alloying. A powder mixture of Mg and Zn with the composition of Mg-10wt%Zn was milled in a planetary mill under argon atmosphere using a stainless steel container and balls. Milling process was carried out at 250rpm for various milling times i.e. 1, 2, 5, 10 and 15hours. 3% n-heptane solution was added prior to milling process to avoid excessive cold welding of the powder. Then, as-milled powder was compacted under 400MPa and sintered in a tube furnace at 350°C in argon flow. The refinement analysis of the x-ray diffraction patterns shows the presence of Mg-Zn solid solution and formation of MgZn2 when Mg-Zn powder was mechanically milled for 2hours and further. A prolonged milling time has increased the density and microhardness of the sintered Mg-Zn alloy.

Liquation Cracking in Arc and Friction-Stir Welding of Mg-Zn Alloys

As compared to Al alloys, which are known to be susceptible to liquation (i.e., liquid formation) and liquation-induced cracking, most Mg alloys have a lower eutectic temperature and thus are likely to be even more susceptible. The present study was conducted to study liquation and liquation cracking in Mg alloys during arc welding and friction-stir welding (FSW). Binary Mg-Zn alloys were selected as a model material in view of their very low eutectic temperature of 613 K (340 °C). Mg-Zn alloys with 2, 4, and 6 wt pct of Zn were cast and welded in the as-cast condition by both gas-tungsten arc welding (GTAW) and FSW. A simple test for liquation cracking was developed, which avoided interference by solidification cracking in the nearby fusion zone. Liquation and liquation cracking in GTAW were found to be in the decreasing order of Mg-6Zn, Mg-4Zn, and Mg-2Zn. Liquation cracking occurred in FSW of Mg-6Zn but not Mg-4Zn or Mg-2Zn. Instead of a continuous ribbon-like flash connected to the weld edge, small chips, and powder covered the weld surface of Mg-6Zn. The results from GTAW and FSW were discussed in light of the binary Mg-Zn phase diagram and the curves of temperature vs fraction solid during solidification.

Zinc Alloys for Biodegradable Medical Implants

Both magnesium and zinc are considered as suitable elements for preparation of biodegradable materials that can be gradually dissolved in human organism without the production of toxic compounds. Although many magnesium-based materials possess good mechanical properties and biocompatibility, corrosion rates accompanied by hydrogen release and pH increase are too high. On the contrary, Zn is characterized by much lower corrosion rate in physiological solution compared to magnesium and its alloys. Therefore, we study Zn-Mg binary alloys with 0-7 wt.% of Mg. In this case, magnesium was selected to improve mechanical properties and biocompatibility of pure Zn. The structures of alloys were studied by an optical metallographic microscope and SEM equipped with EDS analyzer. Mechanical properties were studied using Vickers hardness measurements. Our results showed that mechanical properties of binary Mg-Zn alloys improve with increasing content of Mg, achieving the maximum at eutectic composition. Higher Mg concentrations strongly deteriorate mechanical properties of binary Mg-Zn alloys.

Biocompatibility Assessment of Novel Bioresorbable Alloys Mg-Zn-Se and Mg-Zn-Cu for Endovascular Applications: <i>In Vitro</i> Studies

Previous studies have shown that using biodegradable magnesium alloys such as Mg-Zn and Mg-Zn-Al possess the appropriate mechanical properties and biocompatibility to serve in a multitude of biological applications ranging from endovascular to orthopedic and fixation devices. The objective of this study was to evaluate the biocompatibility of novel as-cast magnesium alloys Mg-1Zn-1Cu wt.% and Mg-1Zn-1Se wt.% as potential implantable biomedical materials, and compare their biologically effective properties to a binary Mg-Zn alloy. The cytotoxicity of these experimental alloys was evaluated using a tetrazolium based- MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and a lactate dehydrogenase membrane integrity assay (LDH). The MTS assay was performed on extract solutions obtained from a 30-day period of alloy immersion and agitation in simulated body fluid to evaluate the major degradation products eluted from the alloy materials. Human foreskin fibroblast cell growth on the experimental magnesium alloys was evaluated for a 72 hour period, and cell death was quantified by measuring lactate dehydrogenase concentrations. Both Mg-Zn-Se and Mg-Zn-Cu alloys exhibit low cytotoxicity levels which are suitable for biomaterial applications. The Mg-Zn-Cu alloy was found to completely degrade within 72 hours, resulting in lower human foreskin fibroblast cell viability. The Mg-Zn-Se alloy was shown to be less cytotoxic than both the Mg-Zn-Cu and Mg-Zn alloys.

Effect of Al Addition on the Precipitation Behavior of a Binary Mg-Zn Alloy

The effect of Al addition on the precipitation behavior of a binary Mg-Zn alloy was investigated based on the changes in the morphology, distribution and element concentration of precipitates formed during aging treatment. The as-cast Mg-6.0 mass%Zn (Mg-6Zn) and Mg-6.0 mass%Zn-3.0 mass%Al (Al-added) were homogenized at 613 K for 48 h and at 673 K for 12 h; they were then solid solution treated at 673 K for 0.5 h and 1 h, respectively. The Mg-6Zn and Al-added alloys were aged at 403 K and 433 K. The peak hardness of the Al-added alloy was higher than that of the Mg-6Zn alloy at each aging temperature. Rod-like, plate-like, blocky, and lath-like precipitates were observed in the Al-added alloy aged at 433 K for 230.4 ks, although the rod-like and plate-like precipitates were observed in the TEM microstructure of the Mg-6Zn alloy aged at 433 K for 360 ks. Moreover, the precipitates in the Al-added alloy were refined and densely distributed compared with those in the Mg-6Zn alloy. The Cliff-Lorimer plots obtained by the EDS analysis of the rod-like <TEX>${\beta}_1^'$</TEX> and plate-like <TEX>${\beta}_2^'$</TEX> phases in the Al-added alloy peak aged at 433 K for 230.4 ks were examined. It was confirmed that the <TEX>${\beta}_2^'$</TEX> phases had higher concentration of solute Al atom than was present in the <TEX>${\beta}_1^'$</TEX> phases, indicating that the properties of precipitates can be changed by Al addition.