Corrosion behavior of glassy Ni55Co5Nb20Ti10Zr10 alloy in 1 N HCl solution studied by potentiostatic polarization and XPS

Corrosion resistance of glassy Ni₅₅Co₅Nb₂₀Ti₁₀Zr₁₀ (at.%) alloy in 1 N HCl solution was investigated with respect to the electrochemical behavior and the compositions of the passive film and the underlying alloy surface just below the passive film. The potentiostatic polarization curve indicated that the alloy was spontaneously passivated with a low passive current density of the order of 10⁻³ A m⁻². The quantitative X-ray photo-electron spectroscopy (XPS) analysis revealed that the thickness of the surface film increased linearly with an anodizing ratio of 1.5 nm V⁻¹. The high corrosion resistance of the glassy alloy was due to the formation of niobium, titanium and zirconium-enriched passive film. The growth mechanism of the passive films is also discussed.     

Formation,ductile deformation behavior and soft-magnetic properties of (Fe,Co,Ni)–B–Si–Nb bulk glassy alloys

Fe-based [(Fe,Co,Ni)_0.75B_0.2Si_0.05]₉₆Nb₄ bulk ferromagnetic glassy alloy rods with the diameters up to 4 mm were synthesized by copper mold casting. The addition of Ni element caused no decrease in glass-forming ability and fracture strength, but increased the compressive deformation ductility of this Fe-based bulk glassy alloy system. The glassy alloy rods exhibit super-high fracture strength over 4000 MPa, high Young's modulus over 200 GPa, elastic strain of 0.02 and plastic strain up to 0.005. The bulk glassy alloys also exhibit good soft-magnetic properties, i.e., high saturation magnetization of 0.8–1.1 T, low coercive force below 3 A/m, and high permeability of 1.6–2.1 × 10⁴ at 1 kHz. The success of synthesizing a super-high strength Fe-based bulk glassy alloy with some compressive plastic strain and good soft-magnetic properties is encouraging for future development of Fe-based bulk glassy alloys as new engineering and functional materials.     

Formation,thermal stability and corrosion behavior of glassy Ti45Zr5Cu45Ni5 alloy

Ti-rich Ti₄₅Zr₅Cu₄₅Ni₅ bulk metallic glass with critical diameter reaching 3 mm and supercooled liquid region of 42 K was prepared by copper mold casting. The glass transition temperature and onset temperature of crystallization are 673 K and 715 K, respectively. The glassy Ti–Zr–Cu–Ni alloy is passive in 3 mass% NaCl, 1 N HCl and 1 N H₂SO₄ solutions, although pitting corrosion occurred by anodic polarization at higher potential in the Cl⁻-containing solutions. Corrosion rates of the glassy Ti₄₅Zr₅Cu₄₅Ni₅ alloy are of the order of 10⁻³ mm/year in the NaCl and H₂SO₄ solutions and about 1 × 10⁻² mm/year in the HCl acid.     

Mo microalloying effect on the glass-forming ability, magnetic, mechanical and corrosion properties of (Fe0.76Si0.096B0.084P0.06)100-xMox bulk glassy alloys

The effect of Mo addition on the glass-forming ability (GFA), magnetic properties, mechanical properties and corrosion resistance of (Fe_0.76Si_0.096B_0.084P_0.06)_100−xMo_x (x = 0, 2, 4 and 6 at.%) bulk glassy alloys (BGAs) with high Fe contents was investigated. The 2 at.% Mo addition makes the alloy composition approach towards a eutectic point, which could result in an increase in the GFA. The BGA rod with diameters up to 3.5 mm was produced by copper mold casting. These BGAs exhibit a rather high saturation magnetization of 0.98-1.51 T and lower coercive force of 1.7-2.1 A/m. A significant improvement in corrosion resistance was observed with microalloying Mo element in 1 N H₂SO₄ solution. Furthermore, these Fe-based BGAs show super-high strength of ∼3.3 GPa and Young's modulus of 200 GPa.     

Cr effects on magnetic and corrosion properties of Fe–Co–Si–B–Nb–Cr bulk glassy alloys with high glass-forming ability

Effects of the Cr addition on glass formation, magnetic and corrosion properties of {[(Fe_0.6Co_0.4)_0.75B_0.2Si_0.05]_0.96Nb_0.04}_100−xCr_x (x = 1, 2, 3, 4 at.%) alloys have been investigated. It was found that the addition of Cr element slightly decreases the glass-forming ability (GFA), but is very effective in increasing corrosion resistance and improving soft magnetic properties for this Fe–Co–B–Si–Nb bulk glassy alloy within the composition range examined. The Fe–Co–B–Si–Nb–Cr alloys exhibit high GFA. Full glassy rods with diameters up to 4 mm can be synthesized by copper mold casting. The Fe-based bulk glassy alloys (BGAs) exhibit a high saturation magnetization of 0.81–0.98 T as well as excellent soft magnetic properties, i.e., extremely low coercive force of 0.6–1.6 A/m and super-high initial permeability of 26,400–34,100. Furthermore, corrosion measurements show that corrosion rate and corrosion current density of these Fe-based BGAs in 0.5 M NaCl solution decrease from 7.0 × 10⁻¹ to 1.6 × 10⁻³ mm/year and 3.9 × 10⁻⁶ to 8.7 × 10⁻⁷ A/cm², respectively, with increasing Cr content from 0 to 4 at.%. The success of synthesizing the new Fe-based BGAs exhibiting simultaneously high GFA as well as excellent good soft magnetic properties combined with high saturation magnetization and enhanced corrosion resistance allows us to expect future progress as a new type of soft magnetic materials.     

Fabrication and characterization of bulk glassy Co40Fe22Ta8B30 alloy with high thermal stability and excellent soft magnetic properties

In this work, Co₄₀Fe₂₂Ta₈B₃₀ alloy as a new bulk metallic glass with a wide supercooled liquid region of 74 K and excellent soft magnetic properties was prepared by the powder metallurgy method. Glassy Co₄₀Fe₂₂Ta₈B₃₀ powders were obtained by ball milling of melt-spun glassy ribbons at a cryogenic temperature and subsequently consolidated by hot pressing into disk-shaped specimens 10 mm in diameter and 2 mm thick. It was found that the new glassy alloy exhibited the largest diameter compared with the other Co-based bulk metallic glasses produced in the well-known Co–Fe–Ta–B alloying system up to now. The influence of the consolidation time on the microstructure and magnetic properties of the bulk samples was investigated by X-ray diffraction, differential scanning calorimetry, vibrating sample magnetometry and Faraday magnetometry. The results indicate that the new alloy exhibits a long incubation time before crystallization upon annealing above the glass transition temperature: noticeably longer than for other known (Co,Fe)-based amorphous alloys. The glassy bulk sample consolidated for 600 s at 923 K had a relative density of 99.2%, a saturation magnetization of 46.6 A m² kg^?1, a Curie temperature of 425 K and a low coercivity of 6 A m^?1. In addition, the new bulk glassy alloy exhibited ultra-high hardness of 13.48 GPa. The mechanisms by which the thermal stability and incubation time prior to crystallization increase are explained in accordance with pair correlation function analysis.     

New nickel-based bulk metallic glasses with extremely high nickel content

The effect of boron addition on glass formation in the Ni₇₀Pd₁₀P₂₀ alloy was investigated. The composition containing 4 at% boron showed an improved glass-forming ability. A glassy Ni₇₀Pd₁₀P₁₆B₄ alloy rod with a diameter of 2.5 mm was prepared by a copper mold casting technique. This is the first time that a Ni-based bulk metallic glass with such an extremely high Ni content of 70 at% has been produced. The obtained glassy Ni₇₀Pd₁₀P₁₆B₄ alloy exhibited rather good mechanical properties and corrosion resistance.     

Enhancement on GFA and mechanical properties of Ni-based bulk metallic glasses through Fe addition

Bulk Ni_76-xFe_xP₁₄B₆Ta₄ (x = 10, 20, 30, all in at.%) glassy alloy rods with diameters of 1.5–3.0 mm are synthesized by combining fluxing treatment and J-quenching technique, and the effects of Fe substitution for Ni on the glass forming ability (GFA), thermal stability, mechanical properties, and corrosion resistance of the present Ni-based bulk metallic glasses (BMGs) have been studied systematically in this work. It is found that the appropriate substitution of Fe for Ni can greatly enhance the GFA of the present Ni-based alloys, and the critical diameter for fully glass formation gets to the maximum value of 3.0 mm when the substitution content of Fe for Ni is 20 at.%. The corrosion tests show that the substitution of Fe for Ni causes a certain reduction of the corrosion resistance of the present Ni-based BMGs, but the corrosion current densities in both 1 M NaCl and 1 M HCl solutions are below the order of magnitude of 10⁻⁵ A/cm² and the corrosion rate in1 M HCl solution is in the order of magnitude of 0.1 mm/year, still exhibiting a good corrosion resistance. The present Ni-based BMGs exhibit a compressive strength of more than 2.6 GPa and, more significantly, the substitution of Fe for Ni greatly enhances the compressive plasticity of the present Ni-based BMGs and the compressive plastic strain gets up to 6.6% when 20 at.% of Ni is substituted by Fe. This work indicates that the GFA and mechanical properties of Ni-based BMGs can be enhanced significantly through the Fe addition.     

Bulk glassy Fe-Cr-Mo-C-B alloys with high corrosion resistance

The preparation of bulk glassy alloys with high glass-forming ability and high corrosion resistance in Fe-based system was succeeded by means of copper-mold casting. The temperature interval of supercooled liquid region (ΔT_x) is as large as 53-62 K and the reduced glass transition temperature (T_g/T_m) is as high as 0.62-0.63 for the cast Fe_50−xCr₁₆Mo₁₆C₁₈B_x (x=4, 6, 8 at.%) glassy alloys. The corrosion rates of the Fe_50−xCr₁₆Mo₁₆C₁₈B_x glassy alloys with a diameter of 1.2 mm were in the range of 10⁻³-10⁻² mm year⁻¹ in 1, 6 and 12 N HCl solutions at 298 K. The bulk glassy alloys are spontaneously passivated in 1 and 6 N HCl solutions with wide passive region and low passive current density. They do not suffer pitting corrosion even when polarized anodicly in 12 N HCl solution up to 1.0 V (Ag/AgCl). The high corrosion resistance is due to the formation of chromium-rich passive films during immersion in HCl solutions. In addition, the increase of boron content in alloys improves the corrosion resistance of the bulk glassy alloys within the composition range examined.     

Consolidation and mechanical properties of ball milled Zr50Cu50 glassy ribbons

Bulk Zr₅₀Cu₅₀ partially crystallized glassy specimens have been produced by powder metallurgy methods. Zr₅₀Cu₅₀ powder has been prepared by controlled milling of melt spun glassy ribbons and subsequently consolidated by hot pressing into bulk cylindrical samples of 10 mm diameter and 10 mm length. The consolidated material exhibits interesting mechanical properties, namely, a perfect elastic regime of 1.5%, high strength of about 1350 MPa and hardness of 4.80 GPa. However, no macroscopic ductility is visible, most likely due to the residual porosity of the consolidated specimens. These results indicate that powder metallurgy methods may become a valid alternative to casting techniques for the production of glassy and partially crystallized Zr-based alloys.     

XPS study on the surface films of a newly designed Ni-free Ti-based bulk metallic glass

The electrochemical and corrosion behavior of a newly designed Ni-free Ti-based bulk metallic glass (BMG) was investigated. The Ti₄₅Zr₁₀Pd₁₀Cu₃₁Sn₄ BMG exhibits excellent corrosion resistance after immersion in 3 mass% NaCl, 1 N H₂SO₄ and 1 N H₂SO₄ + 0.01 N NaCl solutions. X-ray photoelectron spectroscopy measurements were used to analyze the changes of the elements on the alloy surface before and after immersion in various solutions. The formation of Ti- and Zr-enriched highly protective thin surface films is responsible for the high corrosion resistance of this alloy in corrosive solutions.     

Electrochemical behavior and localized corrosion associated with Al7Cu2Fe particles in aluminum alloy 7075-T651

Initiation of localized corrosion upon high strength aluminum alloys is often associated with cathodic intermetallic particles within the alloy. Electrochemical measurements and metallurgical characterization have been made to clarify and quantify the physical properties of Al₇Cu₂Fe particles in AA7075-T651. Prior studies regarding either the stereology or electrochemical properties of Al₇Cu₂Fe are scarce. Quantitative microscopy revealed a significant population of Al₇Cu₂Fe in the alloy; comprising up to 65% of the constituent particle population and typically at a size of 1.7 ± 1.0 μm. It was determined that Al₇Cu₂Fe may serve as a local cathode in the evolution of localized corrosion of AA7075-T651 and is capable of sustaining oxygen reduction reactions at rates of several hundreds of μA/cm² over a range of potentials typical of the open circuit potential (OCP) of AA7075-T651 in NaCl solution of various concentrations and pH. The presence of Al₇Cu₂Fe leads to the development of pitting at the particle–matrix interface.     

Specific volume and elastic properties of glassy,icosahedral quasicrystalline and crystalline phases in Zr–Ni–Cu–Al–Pd alloy

Elastic properties, phase composition, microstructure and specific volume changes in the Zr₆₅Ni₁₀Cu₅Al_7.5 Pd_12.5 glassy alloy during progressive devitrification have been studied by ultrasonic pulse, X-ray diffractometry, transmission electron microscopy and Archimedean methods, respectively, in terms of structure and properties change. On heating the glassy alloy initially forms an icosahedral phase and then a mixture of tI12 Zr₂Ni^ss and β-Zr^ss crystalline phases after annealing at 993 K for 300 s, and lastly tI12 Zr₂Ni^ss, tI6 Zr₂Pd and hP9 Zr₆Al₂Ni crystalline phases after prolonged annealing at 993 K for 7.2 ks. In an as-solidified state the alloy shows high Poisson’s and K/G ratios of 0.42 and 7, respectively. These parameters are responsible for its good ductility. The structural changes are accompanied by decreases in specific volume, bulk modulus, Lamé parameter and Poisson’s ratio. Small specific volume changes upon primary devitrification suggest a close relation between the glassy and the icosahedral structures. The existence of the icosahedral local order, which exhibits rigidity for three-dimensional shear deformation with mixed mode II mode III, may be responsible for good elasticity of the glassy alloy.     

He ion irradiation induced nanocrystallization in Cu50Zr45Ti5 glassy alloy

Partial nanocrystallization induced by ion irradiation can be used to improve the surface properties in metallic glasses. We investigated the crystallization behavior and the structure of the formed nanocrystalline phases in a melt-spun Cu₅₀Zr₄₅Ti₅ glassy alloy irradiated with 140 keV He ions to a fluence of 1.7 × 10¹⁷/cm². Crystalline nanoparticles were precipitated by He ion irradiation. The nanocrystalline phases were identified as a mixture of the orthorhombic Cu₁₀Zr₇ phase, tetragonal CuZr₂ phase and monoclinic CuZr phase. Hardness enhancement was observed at a depth close to the projected range of the He ions, which was related to the formation of the crystalline nanoparticles.     

The corrosion behavior of amorphous and nanocrystalline Fe73.5Cu1Nb3Si15.5B7 alloy

The potentiodynamic polarization curves in 0.5 M NaCl solution before and after crystallization of Fe_73.5Cu₁Nb₃Si_15.5B₇ alloy have been studied in relation to the microstructure and alloy composition. It was shown that the corrosion resistance of the alloy strongly depending on these two factors. The observed decrease in corrosion resistance of the alloy after the heat treatment up to 480 °C in comparison to the corrosion resistance of the alloy in the as prepared state is attributed to the increased inhomogeneity of the alloy that coincides with the first appearance of Fe₃Si phase. Further heating (up to 600 °C) resulted in an increase in the number of Fe₃Si nanocrystallites and the appearance of a FeCu₄ phase. After annealing at 600 °C the lowest corrosion rate, 0.004 mm a⁻¹, was observed. Annealing of the samples at higher temperatures (>600 °C) induced formation of six crystalline phases which proved detrimental to the corrosion resistance of the Fe_73.5Cu₁Nb₃Si_15.5B₇ alloy. Solid corrosion products were identified on the surface of the samples after anodic polarization.     

The corrosion of Fe3Al alloy in liquid zinc

A systematic study of the isothermal corrosion testing and microscopic examination of Fe₃Al alloy in liquid zinc containing small amounts of aluminum (less than 0.2 wt.%) at 450 °C was carried out in this work. The results showed the corrosion of Fe₃Al alloy in molten zinc was controlled by the dissolution mechanism. The alloy exhibited a regular corrosion layer, constituted of small metallic particles (diameter: 2-5 μm) separated by channels filled with liquid zinc, which represented a porosity of about 29%. The XRD result of the corrosion layer formed at the interface confirmed the presence of Zn and FeZn_6.67. The corrosion rate of Fe₃Al alloy in molten zinc was calculated to be approximately 1.5 × 10⁻⁷ g cm⁻² s⁻¹. Three steps could occur in the whole process: the superficial dissolution of metallic Cr in the corrosion layer, the new phase formation of FeZn_6.67 and the diffusion of the dissolved species in the channels of the corrosion layer.     

Structure and crystallization kinetics of a Cu50Zr45Ti5 glassy alloy

The crystallization kinetics and structure changes in a melt-spun Cu₅₀Zr₄₅Ti₅ glassy alloy on heating were investigated by X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and differential isothermal calorimetry. The glassy phase in the Cu₅₀Zr₄₅Ti₅ alloy was crystallized forming Cu₁₀Zr₇ and CuZr₂ phases upon thermal annealing. The activation energy for crystallization obtained by the Arrhenius equation was 435 kJ/mol. The crystallization process took place by nucleation and growth mechanism, and an Avrami exponent of about 3.3 may indicate a three-dimensional interface-controlled growth of nuclei with a decreasing nucleation rate.     

AZ31B镁合金表面火焰喷涂Al-Mg_2Si涂层的耐腐蚀性能

为提高AZ31B镁合金表面的耐腐蚀性能,用火焰喷涂方法在镁合金表面制备Al-Mg_2Si复合涂层。采用XRD、SEM和EDS分析涂层的物相组成、微观组织及元素分布;通过电化学试验测试样品在3.5%NaCl溶液中的腐蚀电位、腐蚀电流密度;通过3.5%NaCl溶液浸泡试验测试样品的腐蚀速率;并测试涂层的显微硬度。结果表明:涂层中的主要物相有Mg_2Si、Al,组织比较致密,元素分布均匀。Tafel极化曲线测试表明,Al-Mg_2Si涂层样品与AZ31B镁合金样品相比腐蚀电位从-1.489 V正移到-1.366 V,腐蚀电流密度从2.817×10~(-3) A/cm~2降低到1.198×10~(-3) A/cm~2。浸泡试验结果表明,喷涂Al-Mg_2Si的镁合金的腐蚀速率明显低于没有喷涂的镁合金。显微硬度测试表明,涂层的显微硬度集中分布在259~308 HV0.05之间,镁合金为50~60 HV0.05。因此在AZ31B镁合金表面火焰喷涂Al-Mg_2Si涂层可以提高其耐腐蚀性能,表面硬度显著提高。     

Crystal structure, thermal expansion and electrical properties of the new Al0.32ErGe2 compound

A new ternary compound Al_0.32ErGe₂ has been synthesized and studied from 298 K to 773 K using X-ray powder diffraction technique. Its structure has been determined at room temperature by Rietveld refinement of X-ray powder diffraction data. The ternary compound Al_0.32ErGe₂ crystallizes in the orthorhombic with the defect CeNiSi₂ structure type (space group Cmcm, a = 0.40701(2) nm, b = 1.60401(9) nm, c = 0.39240(2) nm, Z = 4 and D_calc = 8.326 g/cm³). The average thermal expansion coefficients , and of Al_0.32ErGe₂ are 1.72 × 10⁻⁵ K⁻¹, 1.11 × 10⁻⁵ K⁻¹ and 1.52 × 10⁻⁵ K⁻¹, respectively. The bulk thermal expansion coefficient is 4.35 × 10⁻⁵ K⁻¹. Electrical resistivity of Al_0.32ErGe₂ was measured between 5 K and 300 K.     

Stress corrosion cracking of B13, a new high strength aluminium lithium alloy

The present paper focuses on the study of SCC behaviour of a new Al–Cu–Li alloy. For this purpose, two conventional media – NaCl and NaCl + H₂O₂ – were used for comparison with commercial alloys 7075 and 8090. This new alloy shows lower susceptibility to SCC than conventional alloys as it does not undergo environmentally-induced embrittlement in NaCl solutions and in 1 M NaCl + 0.3% H₂O₂ in which the 7075 and 8090 alloys, respectively, undergo environmentally-induced fracture.Solution composition was modified in order to determine the environmental conditions and strain rates under which this new alloy will crack due to a stress corrosion cracking phenomenon. The addition of 0.6 M sulphates to 1 M NaCl + 0.3% H₂O₂ solution allows the definition of a range of strain rate (between 10⁻⁷ and 10⁻⁶ s⁻¹) in which this new alloy undergoes stress corrosion cracking.