Evaluating the Performance of Aluminum Sacrificial Anodes with Different Concentration of Gallium in Artificial Sea Water

In this manuscript, the influence of gallium content additions of Al-Zn-In-Mg alloy was investigated through electrochemical techniques and microstructure observation in 3.5 wt% NaCl solution. The results indicated that Al-Zn-In-Mg-0.03Ga alloy has the best discharge performance among all alloys. We propose that this is due to the fact that gallium addition to the Al-4Zn-In-Mg alloy improves the discharge activity of the alloy as well as elevating its anodic efficiency. In particular, the effect of gallium addition to improve discharge activity tends to be a parabolic curve, in which there is an increase when the gallium is first added that rises to the maximum anode current efficiency of about 98.25% whenever gallium content is 0.03 wt%.

Composition Regulation and Microstructure Characterization of Fe100-xGax Films in the Manufacturing Industry

Fe100-xGax giant magnetostrictive films (GMF) are attracting ever increasing attention for their potential application to manufacturing integrated magnetostrictive displacement sensors. However, it is difficult to fabricate Fe100-xGax thin films with different compositions at will. The influence of compositions on alloy phases, grain sizes, film surface roughness, and magnetic domains of the films and magnetization of magnetron sputtered Fe100-xGax films was investigated. Changing the ratio of the pure iron slice areas to alloy target areas, the desired film composition was achieved by the improved Mosaic method. The morphologies, magnetic domain structure, microstructure, and compositions of Fe100-xGax films revealed by SEM, EDS, XRD, MFM, VSM, and TEM. The results show that there are <1 1 0 > texture in magnetron sputtered Fe100-xGax films. The sharp peak attributed to the A2 microstructure suggests that the film is crystalline. The magnetic domain structure of Fe100-xGax films presents a network form, and the domain width decreases with the decrease of gallium content. It is also found that the magnetic domains of the films are not uniform. The TEM result shows that there are some strip patterns in the films, and the diffraction ring is discontinuous because of the structure extinction. For a suitable candidate of microdevice applications in MEMS, the optimum composition film should be Fe83.25Ga16.75 film.

Spectroscopy and Microscopy of Corundum from Primary Deposits Found in Greece

Corundum primary deposits in Greece occur in four locations: Paranesti in Drama and Gorgona in Xanthi, both belonging to the wider Rhodope Massif, as well as, Ikaria island and Kinidaros in Naxos island, both belonging to Attic-Cycladic Massif. Eight samples were examined with spectroscopic methods (FTIR, UV-Vis, EDXRF) in order to better characterize these four primary deposits: two pink sapphires from Paranesti, a pink and a blue sapphire from Gorgona, two blue sapphires from Ikaria and three blue sapphires from Kinidaros. Under the microscope, all samples present characteristics linked to post-crystallization deformation, decreasing their gem quality. The FTIR absorption spectra of all samples present in different relative intensities, bands of boehmite, diaspore, goethite, mica and/or chlorite inclusions and CO2 in fluid inclusions. Boehmite and diaspore inclusions are most likely epigenetic. In the UV-Vis spectra, the pink color of the samples is linked with Cr3+ absorptions and the blue color with absorptions due to Fe2+-Ti4+ intervalence charge transfer. EDXRF analyses in the studied samples show relatively high titanium and iron concentrations that are related with mineral inclusions. Gallium is slightly variable in samples from different regions; also, different colored samples from Gorgona present diverse gallium content.

Образование дендритной структуры в кристаллах NiFeGaCo при выращивании способом Степанова

The process of growing crystals of the Ni-Fe-Ga-Co alloy by the Stepanov method has been developed. It was found that the structural perfection is disturbed by the formation of dendrites, which are distributed inhomogeneously both along the length and in the cross sections of the crystals. The blocking effect on the dendrites of crystals of the martensite phase, which appears when the samples are cooled to the temperature of the transition of the crystal to the martensite state, is found. The elemental composition of dendritic formations was studied and it was shown that the iron content in the dendrite is approximately 30% higher, and the gallium content is 40% lower than in the matrix. Based on the modeling of heat transfer processes in the real growth zone, taking into account the experiments performed, recommendations were obtained for suppressing the formation of dendrites

Влияние отжига в постоянном магнитном поле на магнитные свойства сплавов железо--галлий

The concentration dependence of the magnetic properties of iron alloys with 3 – 25 at.% gallium has been studied. It is shown that with increasing gallium content, saturation induction decreases monotonically, but coercive force shows a stepped increase with a jump from 85 to 135 A/m between 12 and 15 at.% Ga. The effect of annealing in a dc magnetic field (magnetic field annealing (MFA)) on the behavior of residual induction and coercive force in samples containing from 3 to 18 at.% of gallium was investigated. After the MFA, in the alloy a magnetic anisotropy is induced: magnetic hysteresis loops become narrower, the residual induction increases and the coercive force decreases. The MFA efficiency reaches a maximum when the gallium content is at 15 – 18 at.%. The features of the structural state in iron-gallium alloys and their role in the formation of the magnetic properties during annealing in the dc magnetic field are discussed.

Effect of Gallium Content and Heat Treatment on the Microstructure and Corrosion Rate of Magnesium Binary Alloys

The microstructure and corrosion rate of as-cast and heat-treated binary Mg-Ga alloys with gallium content ranging from 0.375 to 1.5 wt. % were investigated. The corrosion rate was determined by the weight loss method using a simulated body fluid (SBF). The microstructure of the as-cast alloys showed an α-Mg matrix of dendritic morphology with intermetallic compounds Mg5Ga2 located mainly at the interdendritic regions. The fraction and size of the Mg5Ga2 particles increased with the amount of Ga in the alloy. The grain size decreased as the Ga content was increased. The products formed on the surface of the Mg-Ga alloys after immersion in SBF were MgO, Mg(OH)2, and calcium phosphates. The corrosion rate of the as-cast alloys was dependent on the Ga content. At concentrations lower than 1 wt. % the corrosion rate was similar to that of pure Mg (0.65 mm/year). However, Ga additions higher than 1 wt. % worsened the corrosion resistance. After heat treatment, the corrosion rate of Mg-Ga alloys decreased, and in the case of the alloys with Ga concentrations lower than 1 wt. %, corrosion rate was lower than that of pure Mg. Corrosion of these alloys after heat treatment was uniform.

The Usage of Hydroextrusion for Plastic Deformation of Magnetostrictive Iron-Gallium Alloys

For the first time hydroextrusion process was chosen for Fe-Ga ingots deformation with a gallium content of 19 and 20 at.%. The samples were annealed at 950oC, followed by air cooling. Structure of deformation and primary recrystallyzation were investigated by the method of electron back-scattered diffraction (EBSD). The degree of hydroextrusion deformation achieved was 28 – 42 %. There was not found any crystallographic texture at such degree of deformation. The value of magnetostriction in recrystallization sample was about 100 ppm. Available in literature methods and approaches to creation of the Fe-Ga samples from the point of view of receiving high magnetostriction and also a possibility of machining of the samples are discussed.