Quantitative analysis analysis of element concentration in Al alloy by using laser-induced breakdown spectroscopy

Laser-induced breakdown plasma is produced by using Q-switched Nd: YAG laser operating at 532 nm, which interacts with the Al alloy sample target in air. The spectral lines in the 230-440 nm wavelength range have been identified, and based on the calibration-free method, the mass concentration of Al alloy are obtained, which is in good agreement with the standard value of the sample.

Effect of substituting cerium-rich mischmetal with lanthanum on microstructure and mechanical properties of die-cast Mg-Al-RE alloys

Die-cast Mg-4Al-4RE-0.4Mn (RE = Ce-rich mischmetal) and Mg-4Al-4La-0.4Mn magnesium alloys were prepared successfully and their microstructure, tensile and creep properties have been investigated. The results show that two binary Al-RE phases, Al11RE3 and Al2RE, are formed along grain boundaries in Mg-4Al-4RE-0.4Mn alloy, while the phase compositions of Mg-4Al-4La-0.4Mn alloy mainly consist of alpha-Mg phase and Al11La3 phase. And in Mg-4Al-4La-0.4Mn alloy the Al11La3 phase occupies a large grain boundary area and grows with complicated morphologies, which is characterized by scanning electron microscopy in detail. Changing the rare earth content of the alloy from Ce-rich mischmetal to lanthanum gives a further improvement in the tensile and creep properties, and the later could be attributed to the better thermal stability of Al11La3 phase in Mg-4Al-4La-0.4Mn alloy than that of Al11RE3 phase in Mg-4Al-4RE-0.4Mn alloy.

Effect of iron on grain refinement of high-purity MG-Al alloys

The effect of iron on the grain refinement of high-purity Mg-3%Al and Mg-91%Al alloys has been investigated using anhydrous FeCl3 as an iron additive at 750degreesC in carbon-free aluminium titanite crucibles. It was shown that grain refinement was readily achievable for both alloys. Fe- and Al-rich intermetallic particles were observed in many magnesium grains. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Grain size measurements in Mg-Al high pressure die castings using electron back-scattered diffraction (EBSD)

Optical metallographic techniques for grain-size measurement give unreliable results for high pressure diecast Mg-Al alloys and electron back-scattered diffraction mapping (EBSD) provides a good tool for improving the quality of these measurements. An application of EBSD mapping to this question is described, and data for some castings are presented. Ion-beam milling was needed to prepare suitable samples, and this technique is detailed. As is well-known for high pressure die castings, the grain size distribution comprises at least two populations. The mean grain size of the fine-grained population was similar in both AZ91 and AM60 and in two casting thicknesses (2 mm and 5 mm) and, contrary to previously published reports, it did not vary with depth below the surface.

Grain refinement efficiency and mechanism of aluminium carbide in Mg-Al alloys

Detailed microscopic examination using optical and electron microscopes suggests that Al4C3, often observed in the central regions of magnesium grains on polished sections, is a potent substrate for primary Mg. Calculations of the crystallographic relationships between magnesium and Al4C3 further support the experimental observations. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Heterogeneous nucleation of Mg-Al alloys

Grain size is one of the most important microstructural characteristics determining the mechanical properties and therefore the service performance of polycrystalline materials. Heterogeneous nucleation involves the addition or in situ formation of potent nuclei in the system to promote nucleation events, leading to a fine grain structure. This paper reports experimental results using graphite and SiC as potential grain refining agents to form in situ nuclei for Mg in Mg-Al alloys, and demonstrates the key role of Al4C3 in grain refilling this important alloy system. This insight will contribute to the design and development of the most cost effective, eco-friendly grain refining agents for Mg-Al alloys. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effect of manganese on grain refinement of Mg-Al based alloys

Manganese is a grain refiner for high purity Mg-3%Al, Mg-6%Al, Mg-9%Al, and commercial AZ31 (Mg-3%Al-1%Zn) alloys when introduced in the form of an Al-60%Mn master alloy splatter but the use of pure Mn flakes and ALTAB (TM) Mn75 tablets shows no grain refinement. Long time holding of the melt at 730 degrees C leads to an increase in grain size. The mechanism is attributed to the presence of all epsilon-AlMn phase (hexagonal close-packed) in the master alloy splatter. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Synthesis and Raman spectroscopic study of Mg/Al,Fe hydrotalcites with variable cationic ratios

Hydrotalcites of formula Mg6 (Fe,Al)2(OH)16(CO3).4H2O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio have been successfully synthesised. The XRD patterns show variation in the d-spacing attributed to the size of the cation. Raman and infrared bands in the OH stretching region are assigned to (a) brucite layer OH stretching vibrations (b) water stretching bands and (c) water strongly hydrogen bonded to the carbonate anion. Multiple (CO3)2- symmetric stretching bands suggest that different types of (CO3)2- exist in the hydrotalcite interlayer. Increasing the cation ratio (Mg/Al,Fe) resulted in an increase in the combined intensity of the 2 Raman bands at around 3600 cm-1, attributed to Mg-OH stretching modes, and a shift of the overall band profile to higher wavenumbers. These observations are believed to be a result of the increase in magnesium in the structure. Raman spectroscopy shows a reduction in the symmetry of the carbonate, leading to the conclusion that the anions are bonded to the brucite-like hydroxyl surface and to the water in the interlayer. Water bending modes are identified in the infrared spectra at positions greater than 1630 cm-1, indicating the water is strongly hydrogen bonded to both the interlayer anions and the brucite-like surface.

Molecular structure of Mg-Al, Mn-Al and Zn-Al halotrichites : an infrared spectroscopic study

Near infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to halotrichites of the formula MgAl2(SO4)4∙22H2O, MnAl2(SO4)4∙22H2O and ZnAl2(SO4)4∙22H2O. Comparison of the halotrichites in different spectral regions has shown that the incorporation of a divalent transition metal into the halotrichite structure causes a shift in OH stretching band positions to lower wavenumbers. Therefore, an increase in hydrogen bonded water is observed for divalent cations with a larger molecular mass. XRD has confirmed the formation of halotrichite for all three samples and characteristic peaks of halotrichite have been identified at 18.5 and 24.5° 2θ, along with a group of six peaks between 5 and 15° 2θ. It has been observed that Mg-Al and Mn-Al halotrichite are very similar in structure, while Zn-Al showed several differences particularly in the NIR spectra. This work has shown that halotrichite structures can be synthesised and characterised by infrared and NIR spectroscopy.

Compressive behaviour of nanocrystalline Mg-5Al alloys

Magnesium alloys are attracting increasing research interests due to their low density, high specific strength, good machinability and availability as compared to other structural materials. However, the deformation and failure mechanisms of nanocrystalline (nc) Mg alloys have not been well understood. In this work, the deformation behaviour of nc Mg-5Al alloys was investigated using compression test, with focus on the effects of grain size. The average grain size of the Mg- Al alloy was changed from 13 to 50 nm via mechanical milling. The results showed that grain size had a significant influence on the yield stress and ductility of the Mg alloys, and the materials exhibited increased strain rate sensitivity with a decrease in grain size. The deformation mechanisms were also strongly dependent on the grain sizes.

From spent Mg/Al layered double hydroxide to porous carbon materials

Adsorption has been considered as an efficient method for the treatment of dye effluents, but properdisposal of the spent adsorbents is still a challenge. This work attempts to provide a facile methodto reutilize the spent Mg/Al layered double hydroxide (Mg/Al-LDH) after the adsorption of orange II(OII). Herein, the spent hybrid was carbonized under the protection of nitrogen, and then washedwith acid to obtain porous carbon materials. Thermogravimetric analysis results suggested that thecarbonization could be well achieved above 600◦C, as mass loss of the spent hybrid gradually stabilized. Therefore, the carbonization process was carried out at 600, 800, and 1000 ◦C, respectively. Scanning electron microscope showed that the obtained carbon materials possessed a crooked flaky morphology. Nitrogen adsorption–desorption results showed that the carbon materials had large BET surface area and pore volume, e.g., 1426 m2/g and 1.67 cm3/g for the sample carbonized at 800 ◦C. Moreover, the pore structure and surface chemistry compositions were tunable, as they were sensitive to the temperature. Toluene adsorption results demonstrated that the carbon materials had high efficiency in toluene removal. This work provided a facile approach for synthesizing porous carbon materials using spent Mg/Al-LDH.

Ternary bismuth oxides Bi26â-xMxO40ay (M = Mg, Al, Co and Ni) related to α - Bi2O3

Reaction of Bi2O3 with MgO, NiO, Co3O4 and Al2O3 gives rise to the corresponding ternary bismuth oxides, Bi18Mg8O36, Bi18Ni8O36, Bi20Co6O39 and Bi24Al2O39. These oxides have the general formula Bi26�xMxO40�y and exhibit BCC structures related to α - Bi2O3. In the first three solids, the metal ions, M, replace bismuth randomly at the octahedral 24r sites (space group 123); in the last case, aluminium ions occupy the tetrahedral 2a sites, the phase being isostructural with Bi24Ge2O40. Starting from Bi2O3 and NiO, orthorhombic Bi2Ni2O5 has also been obtained.