• Corrosion Science and Technology
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• 제18권6호
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• pp.243-252
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• 2019

The pitting corrosion and inhibition studies of AZ31B magnesium alloy were investigated in the alkaline solution (pH12) with chloride and inhibitors. The corrosion behavior of passive film with/without Cl^- in the alkaline electrolyte were conducted by polarization curve and immersion tests in the presence of various additives (inhibitors) to clarify the inhibition efficiency of pitting corrosion at higher potential region. Critical concentration of pitting corrosion for Mg alloy was evaluated with 0.005 M NaCl in 0.01 M NaOH on the anodic polarization behavior. Critical pitting of AZ31B Mg alloy in 0.01 M NaOH is a function of chlorides; E_pit = - 1.36 - 0.2 log [Cl^-]. When the Sodium Benzoate (SB) was only used as an inhibitor, a few metastable pits developed on the Mg surface by an immersion test despite no pitting corrosion on the polarization curve meaning that adsorption of SB on the surface is insufficient protection from pitting corrosion in the presence of chloride. The role of SB and Sodium Dodecylbenzenesulfonate (SDBS) inhibitors for the Mg alloy surface in the presence of chloride was suppressed from pitting corrosion to co-adsorb on the Mg alloy surface with strong formation of passive film preventing pitting corrosion.

• 한국분말재료학회지
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• 제7권1호
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• pp.12-18
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• 2000

Effects of the microstrucrure of rapidy solidified Al-Pb-Cu-Mg alloys on the wear investigated. In order to overcome the miscility gap between Al and pb under equilibrium conditions, both in the solid and the liquid states, the alloy were rapidy solidifies to produce them in a segregation-free condition. Although the Pb particles showed relatively fine dispersion in the Al matrix in all the alloys by this process. the Al-16Pb alloy was found to have the most favorable microstructure with discretre with discrete Pb particles of abount 0.5 ${\mu}$m in size. With the addition of Cu and Cu-Mg to Al-16Pb, cellular structures were newly formed; not seen in the binary Al-Pb alloy. Wear properties of the Al-Pb binary alloys measured as a function of the sliding speen, sliding distance, and applied load showed that the Al-16Pb alloy has the best wear resistance, as expected from the fine microstructural features in this alloy. The were resistance of the alloy containing Cu-and Cu-Mg was higher than that of the Al-16Pvb alloy, due to matrix strengthening by precipitation hardeing. The wear mechanism was identified by examining the traces and wear debris.

• 한국표면공학회지
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• 제49권3호
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• pp.231-237
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• 2016

This article reports a new chemical bath for preparing a mirror-like surface of AZ31 Mg alloy. In order to find an appropriate chemical polishing solution, four different acidic solutions of sulphuric acid, nitric acid, acetic acid and a specially designed mixture of nitric acid and acetic acid were investigated in view of the changes in surface appearance, roughness and dissolution rate of AZ31 Mg alloy. The surface scales on AZ31 Mg alloy were readily removed by all the acidic solutions, but a reflective surface was produced only by etching in the specially designed solution, and only after a specific etching time. The surface roughness increased with etching time in sulphuric acid, nitric acid, and acetic acid, but it lowered after a specific etching time in the specially designed mixture of nitric acid and acetic acid. Dissolution rate of the alloy in the specially designed mixture of nitric acid and acetic acid appeared to be more than twice than that in separate nitric acid or acetic acid. In this work, we recommend the mirror-like surface of AZ31 Mg alloy obtained by polishing for an optimum time in a mixture of nitric acid and acetic acid for following surface finishings, chemical conversion coating, electroplating, electrophoretic painting and anodizing treatment.

• 열처리공학회지
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• 제35권5호
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• pp.255-261
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• 2022

In this work, the strain-amplitude independent and strain-amplitude dependent damping capacities of Mg-5%Sn alloy have been investigated as a function of its age-hardening response. The hardness increased with an increase in aging time, reached a peak value after 48 h, and then it gradually decreased. The damping capacities of the Mg-5%Sn alloy exhibited a decreasing tendency in the order of solution-treated, under-aged, peakaged, and over-aged states in the strain-amplitude dependent region, whereas they increased continuously with aging time in the strain-amplitude independent region. The microstructural examination during aging revealed that the lower concentration of Sn solutes in the α-(Mg) matrix and the lower density of the Mg₂Sn precipitate particles may well be the crucial factors for better damping values in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.97-97
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• 2017

This study investigated the corrosion protection by electrodeposited copper layer on AZ31 Mg alloy with and without additional silver layer by immersion test, salt spray test, OCP transient and potentiodynamic polarization experiment. The single electrodeposited Cu layer on AZ31 Mg alloy showed a nodular structure with many imperfections of crevices between the nodules, which resulted in the fast initiation of pitting corrosion within first few hours of immersion. Double-layer coating of Cu and outer Ag layer slightly increased the initiation time for pitting corrosion. Triple-layer coatings of Cu/Ag/Cu exhibited the most efficient corrosion protection of AZ31 Mg alloy, compared to the single- and double-layer coatings. Surface morphology of the outer Cu layer in the triple-layer was changed from the nodular structure to fine particle structure with no crevices due to the presence of an additional Ag layer. Thus, the improved corrosion resistance of AZ31 Mg alloy by electrodeposited Cu/Ag or Cu/Ag/Cu layers is readily ascribed to the decreased number of imperfections in the electrodeposited layers due to the additional silver layer. It is concluded that the additional silver layer provides many nucleation sites for the second Cu plating, resulting in the formation of finer and denser structure than the first Cu electrodeposit.

• 한국자동차공학회논문집
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• 제22권4호
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• pp.30-35
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• 2014

According to weight lightning trend of automobile body, necessity of resistance spot welding (RSW) of Mg alloy on automobile industry is increasing rapidly because of the highest specific strength among commercial metals. Mg alloy has low electric resistance and high thermal conductivity like as Al alloy, so that needs applying high current in short time when welding. Thick oxide film of Mg alloy pollutes the electrodes and makes partial current carrying paths when on welding. Partial current carrying paths signify excessive concentration of current. There can initiate expulsion easily and reduces electrode life rapidly. Generating partial current carrying paths and expulsions are influenced by shapes of electrode. Therefore, electrode life also influenced by shape. In this study, we perform life test of RSW electrode of radius type. Measure tensile shear load and nugget size every spot alternately. As a result, radius type electrode can extend life over twice as dome type electrode.

• Advances in materials Research
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• 제4권2호
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• pp.77-85
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• 2015

The influence of rare earth lanthanum (La) on solidification cooling range, microstructure of aluminum-magnesium (Al-Mg) alloy and mechanical properties were investigated. Five kinds of Al-Mg alloys with rare earth content of La (i.e., 0, 0.5, 1.0, 1.5 and 2.0 wt.%) were prepared. Samples were either slowly cooled in furnace or water cooled. Results indicate that the addition of the rare earth (RE) La can significantly influence the solidification range, the resultant microstructure, and tensile strength. RE La can extend the alloy solidification range, increase the solidification time, and also greatly improve the flow performance. The addition of La takes a metamorphism effect on Al-Mg alloy, resulting in that the finer the grain is obtained, the rounder the morphology becomes. RE La can significantly increase the mechanical properties for its metamorphism and reinforcement. When the La content is about 1.5 wt.%, the tensile strength of Al-Mg alloy reaches its maximum value of 314 MPa.

• 한국표면공학회지
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• 제49권3호
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• pp.238-244
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• 2016

Copper electrodeposition on AZ91 Mg alloy was studied in views of preferential deposition on ${\alpha}$- or ${\beta}$- phases and how to achieve uniform deposition over the entire surface on ${\alpha}$- and ${\beta}$-phases in a cyanide solution. The inhomogeneous microstructure of AZ91 Mg alloy, particularly ${\alpha}$- and ${\beta}$-phases, was found to result in non-uniform deposition of zincate layer, preferential deposition of zincate on ${\beta}$-phases, which leads to non-uniform growth of copper layer during the following electrodeposition process. The preferential depositions of zincate can be attributed to higher cathodic polarizations on the ${\beta}$-phases. Pin-hole defects in the copper electrodeposit were observed at the center of large size ${\beta}$-phase particles which is ascribed to gas bubbles formed at the ${\beta}$-phases. The activation of AZ91 Mg alloy in hydrofluoric acid solution was used to obtain uniform growth of zincate layer on both the ${\alpha}$- and ${\beta}$-phases. By choosing an optimum activation time, a uniform zincate layer was obtained on the AZ91 Mg alloy surface and thereby uniform growth of copper was obtained in a cyanide copper electroplating solution.

• Corrosion Science and Technology
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• 제22권5호
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• pp.387-392
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• 2023

The objective of this study was to evaluate corrosion resistance of Zn-Al-Mg alloy coated steel in residential water with trace quantities of Cl^-. Comparative evaluations were performed using two commercial coated steel products, GI and Galvalume, as reference samples. Examination of corrosion morphology and measurement of weight loss revealed that the Zn-Al-Mg alloy coated steel exhibited higher corrosion resistance than reference samples. This finding suggests that the alloy coated steel possesses long-term corrosion resistance not only in highly Cl^- concentrated environments such as seawater, but also in environments with extremely low levels of Cl^- found in residential water. The primary factor contributing to the superior corrosion resistance of the Zn-Al-Mg alloy coated steel in residential water is the formation of an inhibiting corrosion product composed primarily of two phases: Zn₅(OH)₆(CO₃)₂ and Zn₅(OH)₈Cl₂·H₂O. The preferential dissolution of Mg from the corroded coating layer can increase alkalinity, which might enhance the thermodynamical stability of Zn₅(OH)₆(CO₃)₂.

• 한국재료학회지
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• 제14권1호
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• pp.46-51
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• 2004

The annealing of a Cu(4.5at.% Mg)/$SiO_2$/Si structure in ambient $O_2$, at 10 mTorr, and $300-500^{\circ}C$, allows for the outdiffusion of the Mg to the Cu surface, forming a thin MgO (15 nm) layer on the surface. The surface MgO layer was patterned, and successfully served as a hard mask, for the subsequent dry etching of the underlying Mg-depleted Cu films using an $O_2$ plasma and hexafluoroacetylacetone [H(hfac)] chemistry. The resultant MgO/Cu structure, with a taper slope of about $30^{\circ}C$ shows the feasibility of the dry etching of Cu(Mg) alloy films using a surface MgO mask scheme. A dry-etched Cu(4.5at.% Mg) gate a-Si:H TFT has a field effect mobility of 0.86 $\textrm{cm}^2$/Vs, a subthreshold swing of 1.08 V/dec, and a threshold voltage of 5.7 V. A novel process for the dry etching of Cu(Mg) alloy films, which eliminates the use of a hard mask, such as Ti, and results in a reduction in the process steps is reported for the first time in this work.