Effect of the Ca2Mg6Zn3 Phase on the Corrosion Behavior of Biodegradable Mg-4.0Zn-0.2Mn-xCa Alloys in Hank’s Solution

The effect of the Ca₂Mg₆Zn₃ phase on the corrosion behavior of biodegradable Mg-4.0Zn-0.2Mn-xCa (ZM-xCa, x = 0.1, 0.3, 0.5 and 1.0 wt.%) alloys in Hank’s solution was investigated with respect to phase spacing, morphology, distribution and volume fraction. With the increase in Ca addition, the volume fraction of the Ca₂Mg₆Zn₃ phase increased from 2.5% to 7.6%, while its spacing declined monotonically from 43 μm to 30 μm. The Volta potentials of secondary phases relative to the Mg matrix were measured by using scanning kelvin probe force microscopy (SKPFM). The results show that the Volta potential of the intragranular spherical Ca₂Mg₆Zn₃ phase (+109 mV) was higher than that of the dendritic Ca₂Mg₆Zn₃ phase (+80 mV). It is suggested that the Ca₂Mg₆Zn₃ acted as a cathode to accelerate the corrosion process due to the micro-galvanic effect. The corrosion preferred to occur around the spherical Ca₂Mg₆Zn₃ phase at the early stage and developed into the intragranular region. The corrosion rate increased slightly with increasing Ca content from 0.1 wt.% to 0.5 wt.% because of the enhanced micro-galvanic corrosion effect. The decrease in the phase spacing and sharp increase in the secondary phase content resulted in a dramatic increase in the corrosion rate of the ZM-1.0Ca alloy.     

Non-Isothermal Kinetic Analysis of the Crystallization of Metallic Glasses Using the Master Curve Method

The non-isothermal transformation rate curves of metallic glasses are analyzed with the Master Curve method grounded in the Kolmogorov-Johnson-Mehl-Avrami theory. The method is applied to the study of two different metallic glasses determining the activation energy of the transformation and the experimental kinetic function that is analyzed using Avrami kinetics. The analysis of the crystallization of Cu₄₇Ti₃₃Zr₁₁Ni₈Si₁ metallic glassy powders gives E_a = 3.8 eV, in good agreement with the calculation by other methods, and a transformation initiated by an accelerating nucleation and diffusion-controlled growth. The other studied alloy is a Nanoperm-type Fe₇₇Nb₇B₁₅Cu₁ metallic glass with a primary crystallization of bcc-Fe. An activation energy of E_a = 5.7 eV is obtained from the Master Curve analysis. It is shown that the use of Avrami kinetics is not able to explain the crystallization mechanisms in this alloy giving an Avrami exponent of n = 1.     

Effect of Uniaxial Compressive Stress on Phase Transformation Kinetics of Low-Carbon Steel

To attain microstructure transformation and the kinetics of phase transformation under stress during the annealing process, dilatometric curves of phase transformation for Q235 steel were tested using a Gleeble-3500 thermal-mechanical simulator under different uniaxial compressive stresses. The Johnson–Mehl–Avrami (JMA) model considering impingement correction was applied to study the phase-transformation kinetics during annealing. The results showed that the grain size increased with increasing uniaxial compressive stresses because it provided additional energy for grain growth. Furthermore, the interfacial migration velocity decreased with increasing stress owing to grain coarsening and a decrease in the density of the α/γ boundary. Meanwhile, the stress reduces the sum of the misfit accommodation energy and interface energy caused by the transformation, and the driving force required for the transformation of austenite to ferrite decreases. Hence, it was concluded that uniaxial compressive stress plays a complex role in the phase transformation, which inhibits interfacial migration and the transformation rate while providing additional energy for the transformation.     

The Influence of Rapid Solidification on Corrosion Behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 Alloy for Medical Applications

Biodegradable magnesium alloys with Zn, Yb, Ca and Sr additions are potential materials with increased corrosion resistance in physiological fluids that ensure a controlled resorption process in the human body. This article presents the influence of the use of a high cooling rate on the corrosion behavior of Mg₆₀Zn₂₀Yb_15.7Ca_2.6Sr_1.7 alloy proposed for medical applications. The microstructure of the alloy in a form of high-pressure die-casted plates was presented using scanning electron microscopy in the backscattered electrons (BSEs) mode with energy-dispersive X-ray spectrometer (EDX) qualitative analysis of chemical composition. The crystallization mechanism and thermal properties were described on the basis of differential scanning calorimetry (DSC) results. The corrosion behavior of Mg₆₀Zn₂₀Yb_15.7Ca_2.6Sr_1.7 alloy was analyzed by electrochemical studies with open circuit potential (E_OCP) measurements and polarization tests. Moreover, light microscopy and X-ray photoelectron spectroscopy were used to characterize the corrosion products formed on the surface of studied samples. On the basis of the results, the influence of the cooling rate on the improvement in the corrosion resistance was proved. The presented studies are novel and important from the point of view of the impact of the technology of biodegradable materials on corrosion products that come into direct contact with the tissue environment.     

X-ray Thermo-Diffraction Study of the Aluminum-Based Multicomponent Alloy Al58Zn28Si8Mg6

Newly designed multicomponent light alloys are giving rise to non-conventional microstructures that need to be thoroughly studied before determining their potential applications. In this study, the novel Al₅₈Zn₂₈Si₈Mg₆ alloy, previously studied with CALPHAD methods, was cast and heat-treated under several conditions. An analysis of the phase evolution was carried out with in situ X-ray diffraction supported by differential scanning calorimetry and electron microscopy. A total of eight phases were identified in the alloy in the temperature range from 30 to 380 °C: α-Al, α’-Al, Zn, Si, Mg₂Si, MgZn₂, Mg₂Zn₁₁, and SrZn₁₃. Several thermal transitions below 360 °C were determined, and the natural precipitation of the Zn phase was confirmed after nine months. The study showed that the thermal history can strongly affect the presence of the MgZn₂ and Mg₂Zn₁₁ phases. The combination of X-ray thermo-diffraction with CALPHAD methods, differential scanning calorimetry, and electron microscopy offered us a satisfactory understanding of the alloy behavior at different temperatures.     

Effect of Al2Ca Addition and Heat Treatment on the Microstructure Modification and Tensile Properties of Hypo-Eutectic Al–Mg–Si Alloys

The current study investigated the microstructure modification in Al–6Mg–5Si–0.15Ti alloy (in mass %) through the minor addition of Ca using Mg + Al₂Ca master alloy and heat treatment to see their impact on mechanical properties. The microstructure of unmodified alloy (without Ca) consisted of primary Al, primary Mg₂Si, binary eutectic Al–Mg₂Si, ternary eutectic Al–Mg₂Si–Si, and iron-bearing phases. The addition of 0.05 wt% Ca resulted in significant microstructure refinement. In addition to refinement, lamellar to fibrous-type modification of binary eutectic Al–Mg₂Si phases was also achieved in Ca-added (modified) alloy. This modification was related to increasing Ca-based intermetallics/compounds in the modified alloy that acted as nucleation sites for binary eutectic Al–Mg₂Si phases. The dendritic refinement with Ca addition was related to the fact that it improves the efficacy of Ti-based particles (TiAl₃ and TiB₂) in the melt to act as nucleation sites. In contrast, the occupation of oxide bifilms by Ca-based phases is expected to force the iron-bearing phases (as iron-bearing phases nucleate at oxide films) to solidify at lower temperatures, thus reducing their size. The as-cast microstructure of these alloys was further modified by subjecting them to solution treatment at 540 °C for 6 h, which broke the eutectic structure and redistributed Mg₂Si and Si phases in Al-matrix. Subsequent aging treatment caused a dramatic increase in the tensile strength of these alloys, and tensile strength of 291 MPa (with El% of 0.45%) and 327 MPa (with El% of 0.76%) was achieved for the unmodified alloy and modified alloy, respectively. Higher tensile strength and elongation of the modified alloy than unmodified alloy was attributed to refined dendritic structure and modified second phases.     

Ultrafine-Grained Zn–Mg–Sr Alloy Synthesized by Mechanical Alloying and Spark Plasma Sintering

Zinc materials are considered promising candidates for bioabsorbable medical devices used for the fixation of broken bones or stents. Materials for these applications must meet high mechanical property requirements. One of the ways to fulfil these demands is related to microstructure refinement, particularly the decrease in grain size. In the present work, we combine two powder metallurgy techniques (mechanical alloying—MA, and spark plasma sintering—SPS) to prepare Zn–1Mg–0.5Sr nanograin material. The microstructure of compacted material consisted of Zn grains and particles of Mg₂Zn₁₁ intermetallic phases from 100 to 500 nm in size, which resulted in high values of hardness and a compressive strength equal to 86 HV1 and 327 MPa, respectively. In this relation, the combination of the suggested techniques provides an innovative way to form extremely fine microstructures without significant coarsening during powder compaction at increased temperatures.     

Study on Crystallization Process of Li2O–Al2O3–SiO2 Glass-Ceramics Based on In Situ Analysis

In this paper, we used differential scanning calorimetry (DSC), high-temperature X-ray diffraction (HT-XRD), and confocal scanning laser microscopy (CSLM) to investigate the Li₂O–Al₂O_3–SiO₂ glass crystallization process. At 943 K, lithium disilicate (Li₂Si₂O₅) phase crystals began to precipitate in the Li₂O–Al₂O₃–SiO₂ glass with a crystal size of 50–70 nm. At the temperature of 1009 K, petalite (LiAlSi₄O₁₀) crystals began to precipitate in the vitreous phase, forming composite spherical crystals of LiAlSi₄O₁₀ and Li₂Si₂O₅ with size in the range of 90–130 nm. Furthermore, the Kissinger method and KAS method of the JMAK model were used to calculate the crystallization activation energy and the Avrami index “n”. It was found that the precipitation mechanism of the two kinds of crystals is whole crystallization; accordingly, the selection of crystallization heat treatment system was guided to determine the nucleation and crystallization temperature.     

Mechanical Behavior and Structural Characterization of a Cu-Al-Ni-Based Shape-Memory Alloy Subjected to Isothermal Uniaxial Megaplastic Compression

For the first time, uniaxial megaplastic compression was successfully applied to a polycrystalline shape-memory Cu-Al-Ni-based alloy. The samples before and after uniaxial megaplastic compression were examined by methods of X-ray diffraction, optical, electron transmission, and scanning microscopy. The temperature dependences of electrical resistance and the mechanical properties of the alloys under uniaxial tension were also measured. The mechanical behavior under uniaxial megaplastic compression in isothermal conditions in the range of 300–1073 K was studied using the Instron 8862 electric testing machine. The microstructure, phase composition, and martensitic transformations in the eutectoid alloy (Cu-14wt.%Al–4 wt.%Ni) were studied. The radical refinement of the grain structure of the initial hardened D0₃ austenite was found under controlled isothermal compression, due to dynamic recrystallization in the temperature range 673–1073 K and velocities of 0.5–5 mm/min. Compression at 873–1073 K was accompanied by simultaneous partial pro-eutectoid decomposition with the precipitation of the γ₂ phase. Compression at temperatures of 673 and 773 K—that is, below the eutectoid decomposition temperature (840 K)—was accompanied by the precipitation of disperse γ₂ and α phases, and ultradisperse B2’ particles. Cooling of the deformed alloy to room temperature after performing each regime of compression led to thermoelastic martensitic transformation, together with the precipitation of the β′ and γ′ phases. The formation of a fine-grained structure produced an unusual combination of strength and plasticity of the initially brittle alloy both under controlled uniaxial compression, and during subsequent tensile tests at room temperature.     

Structure,Biodegradation, and In Vitro Bioactivity of Zn–1%Mg Alloy Strengthened by High-Pressure Torsion

The effect of high-pressure torsion (HPT) on the microstructure, phase composition, mechanical characteristics, degradation rate, and bioactive properties of the Zn–1%Mg alloy is studied. An ultrafine-grained (UFG) structure with an average grain size of α-Zn equal to 890 ± 26 nm and grains and subgrains of the Mg₂Zn₁₁ and MgZn₂ phases with a size of 50–100 nm are formed after HPT. This UFG structure leads to an increase in the ultimate tensile strength of the alloy by ~3 times with an increase in elongation to 6.3 ± 3.3% due to the formation of a basal texture. The study of corrosion resistance did not show a significant effect of HPT on the degradation rate of the alloy. In addition, no significant changes in the bioactivity of the alloy after HPT: hemolysis, cellular colonization and Escherichia coli growth inhibition.     

An Enhanced Understanding of the Powder Bed Fusion–Laser Beam Processing of Mg-Y3.9wt%-Nd3wt%-Zr0.5wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

Powder Bed Fusion–Laser Beam (PBF–LB) processing of magnesium (Mg) alloys is gaining increasing attention due to the possibility of producing complex biodegradable implants for improved healing of large bone defects. However, the understanding of the correlation between the PBF–LB process parameters and the microstructure formed in Mg alloys remains limited. Thus, the purpose of this study was to enhance the understanding of the effect of the PBF–LB process parameters on the microstructure of Mg alloys by investigating the applicability of computational thermodynamic modelling and verifying the results experimentally. Thus, PBF–LB process parameters were optimized for a Mg WE43 alloy (Mg-Y_3.9wt%-Nd_3wt%-Zr_0.5wt%) on a commercially available machine. Two sets of process parameters successfully produced sample densities >99.4%. Thermodynamic computations based on the Calphad method were employed to predict the phases present in the processed material. Phases experimentally established for both processing parameters included α-Mg, Y₂O₃, Mg₃Nd, Mg₂₄Y₅ and hcp-Zr. Phases α-Mg, Mg₂₄Y₅ and hcp-Zr were also predicted by the calculations. In conclusion, the extent of the applicability of thermodynamic modeling was shown, and the understanding of the correlation between the PBF–LB process parameters and the formed microstructure was enhanced, thus increasing the viability of the PBF–LB process for Mg alloys.     

The Comparation of Arrhenius-Type and Modified Johnson–Cook Constitutive Models at Elevated Temperature for Annealed TA31 Titanium Alloy

Constitutive models play a significant role in understanding the deformation behavior of materials and in optimizing the manufacturing process. In order to improve the reliability of calculation results, the high temperature flow behavior of TA31 titanium alloy obtained from an annealed hot-rolled plate has been investigated by a Gleeble-3500 thermo-mechanical simulator. The isothermal hot compression tests are conducted in the temperature range of 850 to 1050 °C and the strain rate range from 0.001 to 10 s⁻¹ with a height reduction of 60%. The annealed TA31 shows a dynamic recovery characteristic during thermo-mechanical processing. The experimental data have been used to develop an Arrhenius-type constitutive model and a modified Johnson–Cook model under the consideration of coupling effect on strain, temperature, and strain rate, as well as the strain-softening phenomenon. The material parameters are determined by a global optimization method based on the initial values by means of a regression method. A comparation of the predicted results has been performed based on the modified Johnson–Cook model and those acquired from the Arrhenius-type model. The correlation coefficient and average absolute relative error of the modified Johnson–Cook model are 4.57% and 0.9945, respectively. However, when the optimization method has been applied, they are 15.77% and 0.9620 for the Arrhenius-type model, respectively. These results indicate that the modified Johnson–Cook model is more accurate and efficient in predicting the flow stress of annealed TA31 titanium alloy under a set of model material parameters. Furthermore, the simple mathematical expression of this model is helpful to incorporate it into the finite element software to obtain detailed and valuable information during the thermo-mechanical processing simulation for TA31 in further work.     

Synthesis and Quasi-Static Compressive Properties of Mg-AZ91D-Al2O3 Syntactic Foams

Magnesium alloys have considerably lower density than the aluminum alloy matrices that are typically used in syntactic foams, allowing for greater specific energy absorption. Despite the potential advantages, few studies have reported the properties of magnesium alloy matrix syntactic foams. In this work, Al₂O₃ hollow particles of three different size ranges, 0.106–0.212 mm, 0.212–0.425 mm, and 0.425–0.500 mm were encapsulated in Mg-AZ91D by a sub-atmospheric pressure infiltration technique. It is shown that the peak strength, plateau strength and toughness of the foam increases with increasing hollow sphere wall thickness to diameter (t/D) ratio. Since t/D was found to increase with decreasing hollow sphere diameter, the foams produced with smaller spheres showed improved performance—specifically, higher energy absorption per unit weight. These foams show better performance than other metallic foams on a specific property basis.     

Calculation Based on the Formation of Mg2Si and Its Effect on the Microstructure and Properties of Al–Si Alloys

In order to investigate the effect of Mg₂Si formation on the microstructure and properties of an Al−Si alloy, the critical point of a hypereutectic Al−17Si−4Cu−Mg alloy was calculated by Pandat software. The calculation results of the equilibrium phase diagram show that the critical point for Mg₂Si phase formation for the alloy was obtained when the Mg content was 2.2%. The contents of 0.5 wt.% Mg and 2.5 wt.% Mg were selected as the research object. The content of Mg increased from 0.5 wt.% to 2.5 wt.%, the eutectic Si in the matrix was reduced, and the Chinese character-like Mg₂Si phase appeared in the microstructure. In the peak ageing state, in addition to θ″ and Q′ phases that were mainly precipitated, there was also needle-like β″ precipitation in the 2.5 wt.% Mg content alloy. Larger precipitates were found in 2.5 wt.% content alloys, mainly due to the promotion of the solid solution having the aggregation and segregation of more solute elements in the matrix. The tensile strength, elongation, and hardness of hypereutectic Al−17Si−4Cu−0.5Mg alloy under peak ageing were 331 MPa, 3.11%, and 152.1 HB, respectively. The tensile strength and the elongation decreased while the hardness increased with the 2.5 wt.% Mg content, which is due to the formation of hard and brittle Mg₂Si and Al₈FeMg₃Si, which has a splitting effect on the matrix.     

Characterisation of a Novel Complex Concentrated Alloy for Marine Applications

Complex concentrated alloys (CCAs) are a new family of materials with near equimolar compositions that fluctuate depending on the characteristics and destination of the material. CCAs expand the compositional limits of the traditional alloys, displaying new pathways in material design. A novel light density Al₅Cu_0.5Si_0.2Zn_1.5Mg_0.2 alloy was studied to determine the structural particularities and related properties. The alloy was prepared in an induction furnace and then annealed under a protective atmosphere. The resulted specimens were analysed by chemical, structural, mechanical, and corrosion resistance. The structural analyses revealed a predominant FCC and BCC solid solution structure. The alloy produced a compression strength of 500–600 MPa, comparable with conventional aluminium alloys. The corrosion resistance in 3.5% NaCl solution was 0.3424 mm/year for as-cast and 0.1972 mm/year for heat-treated alloy, superior to steel, making the alloy a good candidate for marine applications.     

Ultralight Functionally Graded Hybrid Nanocomposites Based on Yttrium and Silica-Reinforced Mg10Li5Al Alloy: Thermal and Tribomechanical Properties

Despite the amazing properties of lightweight Mg₁₀Li₅Al alloy, its use in industrial applications is highly limited due to its low mechanical properties, wear resistance, and coefficient of thermal expansion (CTE). In this context, this work aimed to improve the above properties without sacrificing the important benefit of this alloy being lightweight. Therefore, function grade composites (FGCs) were prepared based on the Mg₁₀Li₅Al alloy reinforced by yttrium (Y) and silica fume using the powder metallurgy technique. Then, the nanocomposite’s microstructure, mechanical properties, artificial aging, wear resistance, and thermal expansion were examined. The results indicated that the precipitation (MgAlLi₂), softening (AlLi₂), and Mg₂₄Y₅ phases were formed in high-reinforced samples during high-energy milling. Furthermore, the addition of reinforcements accelerated the decomposition from the MgAlLi₂ phase to the Al–Li phase (softening point). For the layer containing the highest reinforcement content, microhardness, strength, and Young’s modulus improved up to 40, 22.8, and 41%, respectively, due to the combined effect of the high strength of silica fume and the dispersion strengthening Mg₂₄Y₅ phase. Meanwhile, the same sample exhibited a remarkable improvement in wear rate and the CTE value to about 43 and 16.5%, respectively, compared to the non-reinforced alloy.     

Study of Forms of Compounds of Vanadium and Other Elements in Samples of Pyrometallurgical Enrichment of Ash from Burning Oil Combustion at Thermal Power Plants

The results of the processing of ash from the combustion of fuel oil after roasting with the addition of Na₂CO₃ followed by aluminothermic melting are presented. As a result, metallic nickel and vanadium slag were obtained. Studies of slag, metal, and deposits on the electrode were carried out. The resulting metal contains about 90 wt% Ni. The main phases of scurf on the electrode are a solid solution based on periclase (Mg_{1–x–y–z}Ni_xFe_yV_zO), sodium-magnesium vanadate (NaMg₄(VO₄)₃), and substituted forsterite (Mg_2–x–yFe_xNi_ySiO₄). The processing of ash made it possible to significantly increase the concentration of vanadium and convert it into more soluble compounds. Vanadium amount increased from 16.2 in ash to 41.4–48.1 V₂O₅ wt% in slag. The solubility of vanadium was studied during aqueous leaching and in solutions of H₂SO₄ and Na₂CO₃. The highest solubility of vanadium was seen in H₂SO₄ solutions. The degree of extraction of vanadium into the solution during sulfuric acid leaching of ash was 18.9%. In slag, this figure increased to 72.3–96.2%. In the ash sample, vanadium was found in the form of V⁵⁺, V⁴⁺ compounds, vanadium oxides VO₂ (V⁴⁺), V₂O₅ (V⁵⁺), and V₆O₁₃, and nickel orthovanadate Ni₃(VO₄)₂ (V⁵⁺) was found in it. In the slag sample, vanadium was in the form of compounds V⁵⁺, V⁴⁺, V³⁺, and V^(0÷3)+; V⁵⁺ was presented in the form of compounds vanadate NaMg₄(VO₄)₃, NaVO₃, and Ca_xMg_yNa_z(VO₄)₆; V³⁺ was present in spinel (FeV₂O₄) and substituted karelianite (V_{2–x–y–z}Fe_xAl_yCr_zO₃). In the obtained slag samples, soluble forms of vanadium are due to the presence of sodium metavanadate (NaVO₃), a phase with the structure of granate Ca_xMg_yNa_z(VO₄)₆ and (possibly) substituted karelianite (V_{2–x–y–z}Fe_xAl_yCr_zO₃). In addition, spinel phases of the MgAl₂O₄ type beta-alumina (NaAl₁₁O₁₇), nepheline (Na_4–xK_xAl₄Si₄O₁₆), and lepidocrocite (FeOOH) were found in the slag samples.     

Microstructure and Properties of As-Cast and Heat-Treated 2017A Aluminium Alloy Obtained from Scrap Recycling

The continuous increase in the consumption of aluminium and its alloys has led to an increase in the amount of aluminium scrap. Due to environmental protection, and to reduce the costs of manufacturing aluminum in recent years, a lot of research is devoted to recycling of aluminum alloys. The paper presents the results of research concerning the possibility of manufacturing standardized alloy 2017A from commercial and post-production scrap by continuous casting. Obtained from recycling process ingots were subjected to analysis of chemical composition and intermetallic phase composition. Based on the results of light microscopy (LM), scanning electron microscopy + electron dispersive spectroscopy (SEM + EDS), and X-ray diffraction (XRD) the following phases in the as-cast state were identified: θ-Al₂Cu, β-Mg₂Si, Al₇Cu₂Fe, Q-Al₄Cu₂Mg₈Si₇, and α-Al₁₅(FeMn)₃(SiCu)₂. During solution heat treatment most of the primary precipitates of intermetallic phases, like θ-Al₂Cu, β-Mg₂Si, and Q-Al₄Cu₂Mg₈Si₇, were dissolved in the solid solution α-Al, and during natural and artificial aging they precipitate as strengthening phases θ-Al₂Cu and Q-Al₄Cu₂Mg₈Si₇ with high dispersion. The highest hardness—150.3 HB—of 2017A alloy was obtained after solution heat treatment from 510 °C and aging at 175 °C. In the static tensile test the mechanical (R_m and R_p0.₂) and plastic (A₅) properties were determined for 2017A alloy in the cast state and after T4 heat treatment. The highest strength properties—tensile strength R_m = 450.5 MPa and yield strength R₀.₂ = 268.7 MPa with good relative elongation A₅ = 14.65%, were obtained after solution heat treatment at 510 °C/6 h/water quenching and natural aging at 25 °C for 70 h. The alloy manufactured from recycled scrap is characterized by relatively high mechanical properties.     

Synthesis of Zeolites from Fine-Grained Perlite and Their Application as Sorbents

The hydrothermal alteration of perlite into zeolites was studied using a two-step approach. Firstly, perlite powder was transformed into Na-P1 (GIS) or hydro(xy)sodalite (SOD) zeolites at 100 °C and 24 h using 2 or 5 M NaOH solutions. Secondly, the Si:Al molar ratio of the reacted Si-rich solution was adjusted to 1 by Na-aluminate addition to produce zeolite A (LTA) at 65 or 95 °C and 6 or 24 h at an efficiency of 90 ± 9% for Al and 93 ± 6% for Si conversion. The performance of these zeolites for metal ion removal and water softening applications was assessed by sorption experiments using an artificial waste solution containing 4 mmol/L of metal ions (Me²⁺: Ca²⁺, Mg²⁺, Ba²⁺ and Zn²⁺) and local tap water (2.1 mmol/L Ca²⁺ and 0.6 mmol/L Mg²⁺) at 25 °C. The removal capacity of the LTA-zeolite ranged from 2.69 to 2.86 mmol/g for Me²⁺ (=240–275 mg/g), which is similar to commercial zeolite A (2.73 mmol/g) and GIS-zeolite (2.69 mmol/g), and significantly higher compared to the perlite powder (0.56 mmol/g) and SOD-zeolite (0.88 mmol/g). The best-performing LTA-zeolite removed 99.8% Ca²⁺ and 93.4% Mg²⁺ from tap water. Our results demonstrate the applicability of the LTA-zeolites from perlite for water treatment and softening applications.     

The Effect of Sn Addition on Zn-Al-Mg Alloy; Part I: Microstructure and Phase Composition

In this study, the addition of Sn on the microstructure of Zn 1.6 wt.% Al 1.6 wt.% Mg alloy was studied. Currently, the addition of Sn into Zn-Al-Mg based systems has not been investigated in detail. Both as-cast and annealed states were investigated. Phase transformation temperatures and phase composition was investigated via DSC, SEM and XRD techniques. The main phases identified in the studied alloys were η(Zn) and α(Al) solid solutions as well as Mg₂Zn₁₁, MgZn₂ and Mg₂Sn intermetallic phases. Addition of Sn enabled the formation of Mg₂Sn phase at the expense of Mg_xZn_y phases, while the overall volume content of intermetallic phases is decreasing. Annealing did not change the phase composition in a significant way, but higher Sn content allowed more effective spheroidization and agglomeration of individual phase particles.