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Structure and Properties of Crystalline and Amorphous Alloys

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Physics".

Deadline for manuscript submissions: closed (20 April 2022) | Viewed by 29243

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Prof. Dr. Rafał Babilas

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Faculty of Mechanical Engineering, Silesian University of Technology, Gliwice, Poland
Interests: materials engineering; amorphous and nanocrystalline materials; functional materials; nanomaterials; metallic glasses; biomaterials; computer modelling of amorphous structure
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Special Issue Information

Dear Colleagues,

Alloys are used in a wide variety of applications, from the structural alloys used in buildings, automobiles, factories to functional alloys used in medicine, electronic or sport devices. In some cases, a combination of metals and metalloids may reduce the overall cost of the material while maintaining usable properties. The combination of metals and nonmetals allows synergistic properties to the constituent metal elements such as density, conductivity, corrosion resistance, hardness or mechanical strength. It is generally known that preparation of alloys with well-defined structure (e.g., amorphous, nanocrystalline, quasicrystalline or crystalline) is difficult and requires the selection of cooling rates of the liquid metals, annealing or sintering conditions. The formation of amorphous, nanocrystalline or quasicrystalline structure allows to achieve better physicochemical properties compared to their crystalline counterparts.

This Special Issue will focus on research papers on metallic alloys based on light and ferromagnetic metals with amorphous, nanocrystalline, qusicrystalline and crystalline structure. Papers on glassy alloys including conventional and bulk metallic glasses will also be considered, as well as partially glass alloys and nanostructured materials. Papers involving structural and functional alloys with modification of the surface are also included in so far as the mechanical, electrical, magnetic, thermal, and corrosion properties and structural analysis and modeling.

We invite you to contribute full papers, reviews or communications to this Special Issue. In all cases, the papers must demonstrate novelty and importance to the scope.

Prof. Dr. Rafał Babilas
Guest Editor

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Keywords

Alloys based on light and ferromagnetic metals
Crystalline, nanocrystaline, quasicrystalline, and amorphus materials
Conventional and bulk metallic glasses
Mechanical properties
Electrical and magnetic properties
Corrosion resistance
Structural characterization
Modeling of structure

Published Papers (14 papers)

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Research

18 pages, 4031 KiB

Open AccessArticle

Magnetic Anisotropy and Microstructure in Electrodeposited Quaternary Sn-Fe-Ni-Co Alloys with Amorphous Character

by Ernő Kuzmann, Israel Felner, Laura Sziráki, Sándor Stichleutner, Zoltán Homonnay, Mahmoud R. El-Sharif and Colin U. Chisholm

Materials 2022, 15(9), 3015; https://doi.org/10.3390/ma15093015 - 21 Apr 2022

Cited by 1 | Viewed by 1159

Abstract

Sn-Fe-Ni-Co quaternary alloys, in the composition range of 37–44 at% Sn, 35–39 at% Fe, 6–8 at% Ni and 13–17 at% Co, were prepared by direct current (DC) and pulse plating (PP) electrodeposition. The alloy deposits were characterized by XRD, ⁵⁷Fe and ¹¹⁹Sn conversion electron Mössbauer spectroscopy, SEM-EDX and magnetization measurements. XRD revealed the amorphous character of the quaternary alloy deposits. The dominant ferromagnetic character of the deposits was shown by magnetization and Mössbauer spectroscopy measurements. Room temperature Mössbauer spectra showed minor paramagnetic phases, where their occurrences (~3–20%) are correlated to the electrodeposition parameters (J_dep from −16 to −23 mA/cm² for DC, J_pulse from −40 to −75 mA/cm² for PP), the composition and the saturation magnetization (~52–73 emu/g). A considerable difference was found in the magnetization curves applying parallel or perpendicular orientation of the applied fields, indicating magnetic anisotropy both in DC and pulse plated alloy coatings. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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12 pages, 3128 KiB

Open AccessArticle

Study of Bulk Amorphous and Nanocrystalline Alloys Fabricated by High-Sphericity Fe₈₄Si₇B₅C₂Cr₂ Amorphous Powders at Different Spark-Plasma-Sintering Temperatures

by Yannan Dong, Jiaqi Liu, Pu Wang, Huan Zhao, Jing Pang, Xiaoyu Li and Jiaquan Zhang

Materials 2022, 15(3), 1106; https://doi.org/10.3390/ma15031106 - 30 Jan 2022

Cited by 13 | Viewed by 2207

Abstract

The new generation of high-frequency and high-efficiency motors has high demands on the soft magnetic properties, mechanical properties and corrosion resistance of its core materials. Bulk amorphous and nanocrystalline alloys not only meet its performance requirements but also conform to the current technical concept of integrated forming. At present, spark plasma sintering (SPS) is expected to break through the cooling-capacity limitation of traditional casting technology with high possibility to fabricate bulk metallic glasses (BMGs). In this study, Fe₈₄Si₇B₅C₂Cr₂ soft magnetic amorphous powders with high sphericity were prepared by a new atomization technology, and its characteristic temperature was measured by DSC to determine the SPS temperature. The SEM, XRD, VSM and universal testing machine were used to analyze the compacts at different sintering temperatures. The results show that the powders cannot be consolidated by cold pressing (50 and 500 MPa) or SPS temperature below 753 K (glass transition temperature T_g = 767 K), and the tap density is only 4.46 g·cm⁻³. When SPS temperature reached above 773 K, however, the compact could be prepared smoothly, and the density, saturation magnetization, coercivity and compressive strength of the compacts increased with the elevated sintering temperature. In addition, due to superheating, crystallization occurred even when the sintering temperature was lower than 829 K (with the first crystallization onset temperature being T_x1 = 829 K). The compact was almost completely crystallized at 813 K, resulting in a sharp increase in the coercivity of the compact from 55.55 A·m⁻¹ at 793 K to 443.17 A·m⁻¹. It is noted that the nanocrystals kept growing in size as the temperature increased to 833 K, which increased the coercivity remarkably but showed an enhanced saturation magnetization. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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15 pages, 3589 KiB

Open AccessArticle

The Influence of Rapid Solidification on Corrosion Behavior of Mg₆₀Zn₂₀Yb_15.7Ca_2.6Sr_1.7 Alloy for Medical Applications

by Katarzyna Młynarek-Żak, Anna Sypien, Tomasz Czeppe, Anna Bajorek, Aneta Kania and Rafał Babilas

Materials 2021, 14(19), 5703; https://doi.org/10.3390/ma14195703 - 30 Sep 2021

Viewed by 1643

Abstract

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. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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8 pages, 2379 KiB

Open AccessArticle

Microstructure and Its Effect on the Magnetic, Magnetocaloric and Magnetostrictive Properties of Tb₅₅Co₃₀Fe₁₅ Glassy Ribbons

by Xin Wang, Kang-Cheung Chan, Lei Zhao, Ding Ding and Lei Xia

Materials 2021, 14(11), 3068; https://doi.org/10.3390/ma14113068 - 4 Jun 2021

Cited by 6 | Viewed by 1636

Abstract

In the present work, the microstructure and its effect on the magnetic, magnetocaloric, and magnetoelastic properties of the Tb₅₅Co₃₀Fe₁₅ melt-spun ribbon were investigated. The ribbon exhibits typical amorphous characteristics in its X-ray diffraction examination and differential scanning calorimetry measurement. However, the magnetic properties of the ribbon indicate that the ribbon is inhomogeneous in the nanoscale, as ascertained by a high-resolution electron microscope. Compared to the Tb₅₅Co₄₅ amorphous alloy, the Tb₅₅Co₃₀Fe₁₅ ribbon shows poor magnetocaloric properties but outstanding magnetostriction. A rather high value of reversible magnetostriction up to 788 ppm under 5 T was obtained. The mechanism for the formation of nanoparticles and its effect on the magnetocaloric and magnetostrictive properties were investigated. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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15 pages, 6133 KiB

Open AccessArticle

Microstructure Development and Properties of the Two-Component Melt-Spun Ni₅₅Fe₂₀Cu₅P₁₀B₁₀ Alloy at Elevated Temperatures

by Krzysztof Ziewiec, Mirosława Wojciechowska, Irena Jankowska-Sumara, Aneta Ziewiec and Sławomir Kąc

Materials 2021, 14(7), 1741; https://doi.org/10.3390/ma14071741 - 1 Apr 2021

Viewed by 1547

Abstract

The aim of this work was to investigate the features of microstructure, phase composition, mechanical properties, and thermal stability of the two-component melt-spun Ni55Fe20Cu5P10B10 alloy. The development of the microstructure after heating to elevated temperatures was studied using scanning electron microscope and in situ high temperature X-ray diffraction. The high-temperature behavior of the two-component melt-spun Ni55Fe20Cu5P10B10 alloy and Ni40Fe40B20, Ni70Cu10P20, and Ni55Fe20Cu5P10B10 alloys melt-spun from single-chamber crucible was investigated using differential scanning calorymetry at different heating rates and by dynamic mechanical thermal analysis. The results show that band-like microstructure of the composite alloy is stable even at 800 K, although coarsening of bands forming the microstructure of the ribbons is observed above 550 K. Plastic deformation is observed in the composite previously heated to temperatures of 600–650 K. The properties of the composite alloy are generally different than the properties obtained for the melt-spun alloy of the same average nominal composition produced traditionally. Additionally, the mechanical and the thermal properties in this composite are inherited from the amorphous state of alloys that are precursors for two-component melt spinning (TCMS) processing. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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12 pages, 2922 KiB

Open AccessArticle

Glass-Forming Ability and Corrosion Resistance of Al₈₈Y_8−xFe_4+x (x = 0, 1, 2 at.%) Alloys

by Rafał Babilas, Monika Spilka, Katarzyna Młynarek, Wojciech Łoński, Dariusz Łukowiec, Adrian Radoń, Mariola Kądziołka-Gaweł and Piotr Gębara

Materials 2021, 14(7), 1581; https://doi.org/10.3390/ma14071581 - 24 Mar 2021

Cited by 12 | Viewed by 2059

Abstract

The effect of iron and yttrium additions on glass forming ability and corrosion resistance of Al₈₈Y_8-xFe_4+x (x = 0, 1, 2 at.%) alloys in the form of ingots and melt-spun ribbons was investigated. The crystalline multiphase structure of ingots and amorphous-crystalline structure of ribbons were examined by a number of analytical techniques including X-ray diffraction, Mössbauer spectroscopy, and transmission electron microscopy. It was confirmed that the higher Fe additions contributed to formation of amorphous structures. The impact of chemical composition and structure of alloys on their corrosion resistance was characterized by electrochemical tests in 3.5% NaCl solution at 25 °C. The identification of the mechanism of chemical reactions taking place during polarization test along with the morphology and internal structure of the surface oxide films generated was performed. It was revealed that the best corrosion resistance was achieved for the Al₈₈Y₇Fe₅ alloy in the form of ribbon, which exhibited the lowest corrosion current density (j_corr = 0.09 μA/cm²) and the highest polarization resistance (R_p = 96.7 kΩ∙cm²). Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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18 pages, 9268 KiB

Open AccessEditor’s ChoiceArticle

Surface Modification of Biomedical MgCa_4.5 and MgCa_4.5Gd_0.5 Alloys by Micro-Arc Oxidation

by Piotr Sakiewicz, Krzysztof Piotrowski, Anna Bajorek, Katarzyna Młynarek, Rafał Babilas and Wojciech Simka

Materials 2021, 14(6), 1360; https://doi.org/10.3390/ma14061360 - 11 Mar 2021

Cited by 6 | Viewed by 1694

Abstract

The aim of this work was to characterize the structure and corrosion properties of the MgCa_4.5(Gd_0.5) alloys surface treated by the micro-arc oxidation (MAO) process. The MgCa_4.5 and MgCa_4.5Gd_0.5 alloy samples were processed by MAO in an electrolyte composed of NaOH (10 g/dm³), NaF (10 g/dm³), NaH₂PO₄ (5 g/dm³), Na₂SiO₂·5H₂O (10 g/dm³) and water. Two different voltages (120 V and 140 V) were used in the MAO process. The alloys protected by an oxide layer formed in the MAO were then the subject of corrosion resistance tests in an environment simulating the human body (Ringer’s solution). After the experiments, the resulting samples were investigated using SEM, XPS and EDS techniques. The addition of Gd affected the fragmentation of the coating structure, thereby increasing the specific surface; higher voltages during the MAO process increased the number and size of surface pores. Corrosion tests showed that the MgCa_4.5Gd_0.5 alloys were characterized by low polarization resistances and high corrosion current densities. The studies indicated the disadvantageous influence of gadolinium on the corrosion resistance of MgCa_4.5 alloys. The immersion tests confirmed lower corrosion resistance of MgCa_4.5Gd_0.5 alloys compared to the referenced MgCa_4.5 ones. The MgCa_4.5 alloy with the MAO coating established at voltage 140 V demonstrated the best anticorrosion properties. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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11 pages, 4967 KiB

Open AccessArticle

Structural Characterization of Al₆₅Cu₂₀Fe₁₅ Melt-Spun Alloy by X-ray, Neutron Diffraction, High-Resolution Electron Microscopy and Mössbauer Spectroscopy

by Rafał Babilas, Katarzyna Młynarek, Wojciech Łoński, Dariusz Łukowiec, Mariola Kądziołka-Gaweł, Tomasz Czeppe and László Temleitner

Materials 2021, 14(1), 54; https://doi.org/10.3390/ma14010054 - 24 Dec 2020

Cited by 1 | Viewed by 2408

Abstract

The aim of the work was to characterize the structure of Al₆₅Cu₂₀Fe₁₅ alloy obtained with the use of conventional casting and rapid solidification-melt-spinning technology. Based on the literature data, the possibility of an icosahedral quasicrystalline phase forming in the Al-Cu-Fe was verified. Structure analysis was performed based on the results of X-ray diffraction, neutron diffraction, ⁵⁷Fe Mössbauer and transmission electron microscopy. Studies using differential scanning calorimetry were carried out to describe the crystallization mechanism. Additionally, electrochemical tests were performed in order to characterize the influence of the structure and cooling rate on the corrosion resistance. On the basis of the structural studies, the formation of a metastable icosahedral phase and partial amorphous state of ribbon structure were demonstrated. The possibility of the formation of icosahedral quasicrystalline phase I-AlCuFe together with the crystalline phases was indicated by X-ray diffraction (XRD), neutron diffraction (ND) patterns, Mössbauer spectroscopy, high-resolution transmission electron microscopy (HRTEM) observations and differential scanning calorimetry (DSC) curves. The beneficial effect of the application of rapid solidification on the corrosive properties was also confirmed. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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11 pages, 4146 KiB

Open AccessArticle

Fe-Co-B Soft Magnetic Ribbons: Crystallization Process, Microstructure and Coercivity

by Anna Wojcik, Wojciech Maziarz, Maciej Kowalczyk, Robert Chulist, Maciej Szlezynger, Pawel Czaja, Lukasz Hawelek, Przemyslaw Zackiewicz, Patryk Wlodarczyk and Aleksandra Kolano-Burian

Materials 2020, 13(7), 1639; https://doi.org/10.3390/ma13071639 - 2 Apr 2020

Cited by 2 | Viewed by 2538

Abstract

In this work, a detailed microstructural investigation of as-melt-spun and heat-treated Fe₆₇Co₂₀B₁₃ ribbons was performed. The as-melt-spun ribbon was predominantly amorphous at room temperature. Subsequent heating demonstrated an amorphous to crystalline α-(Fe,Co) phase transition at 403 °C. In situ transmission electron microscopy observations, carried out at the temperature range of 25–500 °C and with the heating rate of 200 °C/min, showed that the first crystallized nuclei appeared at a temperature close to 370 °C. With a further increase of temperature, the volume of α-(Fe,Co) crystallites considerably increased. Moreover, the results showed that a heating rate of 200 °C/min provides for a fine and homogenous microstructure with the α-(Fe,Co) crystallites size three times smaller than when the ribbon is heated at 20 °C/min. The next step of this research concerned the influence of both the annealing time and temperature on the microstructure and coercivity of the ribbons. It was shown that annealing at 485 °C for a shorter time (2 s) led to materials with homogenous distribution of α-(Fe,Co) crystallites with a mean size of 30 nm dispersed in the residual amorphous matrix. This was reflected in the coercivity (20.5 A/m), which significantly depended on the volume fraction of crystallites, their size, and distribution. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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13 pages, 5511 KiB

Open AccessArticle

Influence of Cu Content on Structure and Magnetic Properties in Fe_86-xCu_xB₁₄ Alloys

by Tymon Warski, Patryk Wlodarczyk, Marcin Polak, Przemyslaw Zackiewicz, Adrian Radon, Anna Wojcik, Maciej Szlezynger, Aleksandra Kolano-Burian and Lukasz Hawelek

Materials 2020, 13(6), 1451; https://doi.org/10.3390/ma13061451 - 23 Mar 2020

Cited by 12 | Viewed by 2296

Abstract

Influence of Cu content on thermodynamic parameters (configurational entropy, Gibbs free energy of mixing, Gibbs free energy of amorphous phase formation), crystallization kinetics, structure and magnetic properties of Fe_86-xCu_xB₁₄ (x = 0, 0.4, 0.55, 0.7, 1) alloys is investigated. The chemical composition has been optimized using a thermodynamic approach to obtain a minimum of Gibbs free energy of amorphous phase formation (minimum at 0.55 at.% of Cu). By using differential scanning calorimetry method the crystallization kinetics of amorphous melt-spun ribbons was analyzed. It was found that the average activation energy of α-Fe phase crystallization is in the range from 201.8 to 228.74 kJ/mol for studied samples. In order to obtain the lowest power core loss values, the isothermal annealing process was optimized in the temperature range from 260 °C to 400 °C. Materials annealed at optimal temperature had power core losses at 1 T/50 Hz—0.13–0.25 W/kg, magnetic saturation—1.47–1.6 T and coercivity—9.71–13.1 A/m. These samples were characterized by the amorphous structure with small amount of α-Fe nanocrystallites. The studies of complex permeability allowed to determine a minimum of both permeability values at 0.55 at.% of Cu. At the end of this work a correlation between thermodynamic parameters and kinetics, structure and magnetic properties were described. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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14 pages, 5046 KiB

Open AccessArticle

Effect of the Thickness of TiO₂ Films on the Structure and Corrosion Behavior of Mg-Based Alloys

by Aneta Kania, Piotr Nolbrzak, Adrian Radoń, Aleksandra Niemiec-Cyganek and Rafał Babilas

Materials 2020, 13(5), 1065; https://doi.org/10.3390/ma13051065 - 28 Feb 2020

Cited by 7 | Viewed by 1879

Abstract

This article discusses the influence of the thickness of TiO₂ films deposited onto MgCa2Zn1 and MgCa2Zn1Gd3 alloys on their structure, corrosion behavior, and cytotoxicity. TiO₂ layers (about 200 and 400 nm thick) were applied using magnetron sputtering, which provides strong substrate adhesion. Such titanium dioxide films have many attractive properties, such as high corrosion resistance and biocompatibility. These oxide coatings stimulate osteoblast adhesion and proliferation compared to alloys without the protective films. Microscopic observations show that the TiO₂ surface morphology is homogeneous, the grains have a spherical shape (with dimensions from 18 to 160 nm). Based on XRD analysis, it can be stated that all the studied TiO₂ layers have an anatase structure. The results of electrochemical and immersion studies, performed in Ringer’s solution at 37 °C, show that the corrosion resistance of the studied TiO₂ does not always increase proportionally with the thickness of the films. This is a result of grain refinement and differences in the density of the titanium dioxide films applied using the physical vapor deposition (PVD) technique. The results of 24 h immersion tests indicate that the lowest volume of evolved H₂ (5.92 mL/cm²) was with the 400 nm thick film deposited onto the MgCa2Zn1Gd3 alloy. This result is in agreement with the good biocompatibility of this TiO₂ film, confirmed by cytotoxicity tests. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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7 pages, 1814 KiB

Open AccessFeature PaperArticle

Effect of Co Substitution on Crystallization and Magnetic Behavior of Fe_85.45−xCo_xCu_0.55B₁₄ Metallic Glass

by Lukasz Hawelek, Tymon Warski, Patryk Wlodarczyk, Marcin Polak, Przemyslaw Zackiewicz, Adrian Radon, Anna Wojcik and Aleksandra Kolano-Burian

Materials 2020, 13(4), 919; https://doi.org/10.3390/ma13040919 - 19 Feb 2020

Cited by 5 | Viewed by 1970

Abstract

The effects of Co for Fe substitution on magnetic properties, thermal stability and crystal structure of Fe_85.45−xCo_xCu_0.55B₁₄ (x = 0, 2.5, 5, 7.5, 10) melt spun amorphous alloys were investigated. The Cu content was firstly optimized to minimize the energy of amorphous phase formation by the use of a thermodynamic approach. The formation of crystalline α-Fe type phase has been described using differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. The classical heat treatment process (with heating rate 10 °C/min) in vacuum for wound toroidal cores was optimized in the temperature range from 280 to 430 °C in order to obtain the best magnetic properties (magnetic saturation Bs and coercivity Hc obtained from the B(H) dependencies) at 50 Hz frequency. For optimal heat-treated samples, the complex magnetic permeability in the frequencies 10⁴–10⁸ Hz at room temperature was measured. Finally, magnetic core losses were obtained for 1 T/50 Hz and 1.5 T/50 Hz values for samples annealed at T = 310 °C. An analysis of transmission electron microscope images and electron diffraction patterns confirmed that high magnetic parameters are related to the coexistence of the amorphous and nanocrystalline phases. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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11 pages, 2978 KiB

Open AccessArticle

Correlation between High Temperature Deformation and β Relaxation in LaCe-Based Metallic Glass

by Yinghong Chen and Jichao Qiao

Materials 2020, 13(4), 833; https://doi.org/10.3390/ma13040833 - 12 Feb 2020

Cited by 8 | Viewed by 2345

Abstract

High-temperature deformation around the glass transition temperature T_g and the dynamic mechanical behavior of La₃₀Ce₃₀Al₁₅Co₂₅ metallic glass were investigated. According to dynamic mechanical analysis (DMA) results, La₃₀Ce₃₀Al₁₅Co₂₅ metallic glass exhibits a pronounced slow β relaxation process. In parallel, strain-rate jump experiments around the glass transition temperature were performed in a wide range of strain rate ranges. The apparent viscosity shows a strong dependence on temperature and strain rate, which reflects the transition from non-Newtonian to Newtonian flow. At low strain or high temperature, a transition was observed from a non-Newtonian viscous flow to Newtonian viscous flow. It was found that the activation volume during plastic deformation of La₃₀Ce₃₀Al₁₅Co₂₅ metallic glass is higher than that of other metallic glasses. Higher values of activation volume in La₃₀Ce₃₀Al₁₅Co₂₅ metallic glass may be attributed to existence of a pronounced slow β relaxation. It is reasonable to conclude that slow β relaxation in La₃₀Ce₃₀Al₁₅Co₂₅ metallic glass corresponds to the “soft” regions (structural heterogeneities) in metallic glass. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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13 pages, 3812 KiB

Open AccessArticle

Study of the Morphology and Properties of Biocompatible Ca-P Coatings on Mg Alloy

by Katarzyna Cesarz-Andraczke, Ryszard Nowosielski, Marcin Basiaga and Rafał Babilas

Materials 2020, 13(1), 2; https://doi.org/10.3390/ma13010002 - 18 Dec 2019

Cited by 8 | Viewed by 1989

Abstract

Magnesium alloys are considered as potential biomaterials for use in orthopedic implantology. The main barrier to the use of Mg alloys in medicine is their overly fast and irregular degradation in body fluids. The use of protective calcium phosphate coatings to increase the corrosion resistance of Mg alloy (AM50 alloy: 4 wt.% Al, 0.3 wt.% Mn, 0.2 wt.% Zn, rest Mg) was examined in this study. The scientific goal of the study was the assessment of the influence of calcium phosphate layer morphology on the corrosion process in Ringer’s solution. Modification of the coating morphology was obtained by changing the chemical composition of the phosphatizing bath using NaOH (NaAM50 sample) or ZnSO₄ (ZnAM50 sample). In practice, a more dense and uniform coating could be obtained by the immersion of AM50 alloy in a solution containing ZnSO₄ (ZnAM50 sample). In this study, an adhesion test performed on the ZnAM50 sample indicated that the critical load was 1.35 N. XRD phase analysis confirmed that the obtained coatings included dicalcium phosphate dihydrate (CaHPO₄*2H₂O). The coatings prepared on the NaAM50 and ZnAM50 samples are effective barriers against the progress of corrosion deeper into the substrate. After 120 h immersion in Ringer’s solution, the volume of the evolved hydrogen was 5.6 mL/cm² for the NaAM50 and 3.4 mL/cm² for the ZnAM50 sample. Full article

(This article belongs to the Special Issue Structure and Properties of Crystalline and Amorphous Alloys)

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