Papers by Keyword: Magnesium

Abstract: This study selected sodium silicate, sodium fluoride, glycerol hydroxyl acid, potassium hydroxide and phosphine oxide (LAP) as the stabilizer electrolyte, and then on micro-arc oxidation of magnesium with constant current density. The microstructure, corrosion resistance, chemical composition, structure and characterization of micro-arc oxidation film were determined by SEM and anodic oxidation methods. Experimental results indicated that the test pieces of magnesium would formed an silver-gray uniform densification oxide film on the surface by micro-arc oxidation treatment, and the corrosion resistance of magnesium film-formed had increased by potentiodynamic polarization curve testing.

Abstract: Density functional theory (DFT) calculations were performed on seven magnesium surfaces of Mg(100), Mg(010), Mg(001), Mg(110), Mg(101), Mg(011) and Mg(111). The electronic state density was analyzed. The stabilities of the seven surfaces were established. The results indicated that the surface energies are in the range of 0.4610 to 1.0940 J/m², which correspond to the Mg(001) and Mg(101) surfaces respectively. These data agree well with the available experimental result. In addition, it was found that the lower surface energy corresponds to more evenly distributed density of state (DOS), more number of DOS peaks but less height of it.

Abstract: The reduction ratio was compared between the Pidgeon process and the aluminothermic reduction process with CA₂, CA, C₁₂A₇ as the main production in the residue. The results of XRD show that the main phase in the reduction residue is CA₂, CA, C₁₂A₇ and Ca₂SiO₄, respectively. Consideration of the efficiency of extracting magnesium, the aluminothermic reduction process which is CA₂ as the main phase in the reduction residue, is the best one.

Abstract: The present paper focuses on the experimental investigation of the aluminothermic reduction of magnesia under vacuum condition with the fixed magnesia to aluminum molar ratio of 11:6. The influences of reaction temperature and time on the reduction ratio of magnesia were studied. The chemical composition, phase constitution and morphology of the condensed magnesium and the briquettes after thermal reduction were investigated by X-ray diffraction, scanning electron microscopy equipped with energy dispersive spectrometry. The reduction ratio of magnesia increases with the increase in the reaction temperature and time. The briquettes after thermal reduction at 1050°C-1150°C are mainly composed of the spinel, unreacted magnesia and aluminum. The briquette after 1 hrs thermal reduction at 1200°C contains corundum, magnesium aluminium oxide, trace amount of spinel, unreacted MgO and aluminium.

Abstract: Due to the low density and high specific strength, magnesium and its alloys have been extensively used in the automobile and aerospace applications, where the weight reduction is critical. However, they are highly prone to corrosion, which has greatly limited their application in the automotive and aerospace industries. This paper briefly reviews the technologies for improving the corrosion and wear resistance of magnesium alloys and finds that the widespread application of magnesium alloys is still limited by the lack of proper protective coatings. Therefore, there is still a need to explore new materials and methods for the effective protection of magnesium and its alloys.

Abstract: Recrystallization kinetics of Mg alloy has been investigated in this study. Mg alloys such as Mg-3Al and Mg-6Al in weight percents were cast into rectangular shaped ingots of 20mm thickness. Solution treatment at 400°C for 24 hrs has been carried out on these ingots and pure Mg for comparison. Heat treated ingots including pure Mg were rolled at room temperature by thickness reductions of 10, 20, and 30 percents. Annealing treatment for recrystallization has been conducted on these cold-rolled plates at temperatures of 200, 300, and 400°C for various times from 1 min to 24 hrs. The microstructure observation and hardness measurement conducted on the recrystallized specimens revealed that static recrystallization at 200°C was very slow and expedited with increasing temperature, regardless of Al contents. While recrystallization behavior of Mg at 300°C appeared to be retarded by increase in Al contents, that of Mg was not affected at 400°C.

Abstract: The ionic substitutions have been proposed as a tool to improve the biological performance of hydroxyapatite (HAp) based materials. In the present work, the systems of Ca_(10-x)Mg_x(PO₄)₆(OH)₂ (MgHAp, x = 0, 1, 2, and 3) were successfully synthesized by solgel method. To obtain nanocrystalline of MgHAp, the prepared precursors were calcined in air at 600 °C for 2 h. The samples were characterized by Xray diffraction (XRD) and transmission electron microscope (TEM) observation. The XRD results confirm the formation of pure phase of HAp with the lattice parameter a in the range of 0.94170.9479 nm and c of 0.68410.6919 nm. The crystallite sizes of the powder are found to be 3546 nm as evaluated by the XRD line broadening method. The morphology of the samples are spherical shape of diameter less than 100 nm as evaluated by TEM. The corresponding selected area electron diffraction (SAED) analysis further confirms the formation of hexagonal structure of HAp.

Abstract: Recrystallization nucleates at heterogeneities. The impact of this on local texture and stress-strain response in hot worked magnesium is considered in the present paper. Two aspects of bulge nucleation during dynamic recrystallization are considered.

Abstract: The influence of temperature, grain size and strain rate on superplasticity of magnesium is investigated. Different approaches are compared along with their experimental results to show the variation in the amount of superplasticity by varying above mentioned parameters. At room temperature magnesium alloys usually have poor formability but recent studies of some alloys such as ZE10, AZ31, AZ61 AZ60, AZ80 and AZ91 are pointing that by varying the temperature along with grain size and strain rate improved formability is possible or even superplastic forming of these alloys can be achieved to meet the demands of automotive, aircraft and other weight conscious industries.

Abstract: The current work investigates anisotropy and forming characteristics of ZE10 Mg alloy. Anisotropic effects are measured by analysing tensile tests data for the specimens from 0o, 45o and 90o rolling directions of thin sheet of 0.8 mm thickness. The effects of temperature and strain rates are also included in anisotropic analyses. The mechanical properties of ZE10 alloy are affected by the physical conditions like temperature and strain rates. The effect is significant on yield strength, UTS and fracture strain while small variation is observed in case of Young’s modulus. Deep drawing experiments have been done to investigate the effects of temperature on forming characteristics and limit drawing ratio (LDR) of an alloy. Forming investigation shows that it is difficult to produce a good or unfractured part at 100 oC, but it can be produce at 150 oC or higher with different combinations of blank holder force and drawing ratio. Also, LDR and blank holder force also effects required punch force.