Magnesium alloys stages

De, A. K., A. Mukhopadhyay et al. 2004. Numerical simulation of early stages of oxide formation in molten aluminium-magnesium alloys in a reverberatory furnace. Modell. Simul. Mater. Sci. Eng. 12(3) 389-405. 

Zhang, G. D., Huang, J. J., Yang, K, Zhang, B. C. Ai, H. J. (2007) Experimental study of in vivo implantation of a magnesium alloy at early stage. Acta Metallurgica Sinica, 43, 1186-90. 

Accidental contact of the molten alloy (26% Al) with a wet rusty iron surface caused violent explosions with brilliant light emission. Initial evolution of steam, causing fine dispersion of the alloy, then interaction of the fine metals with rust in a thermite reaction, were postulated as likely stages. Direct interaction of the magnesium (74%) with steam may also have been involved. 

Metallic magnesium is produced by either chemical or electrolytic reduction of its compounds. In chemical reduction, magnesium oxide is obtained from the decomposition of dolomite. Then ferrosilicon, an alloy of iron and silicon, is used to reduce the MgO at about 1200°C. At this temperature, the magnesium produced is immediately vaporized and carried away. The electrolytic method uses seawater as its principal raw material. The first stage is the precipitation of magnesium hydroxide with slaked lime (calcium hydroxide) ... 

The last stage of the process is the final caustic clean, which removes any trace impurity of elements such as antimony, calcium, magnesium, and zinc that may have passed through from the previous processes. The metal is pumped from the de-bismuthizing area to the final kettles where it is held at about 500°C. Caustic soda is added and stirred into the lead for about one hour. Samples are taken at regular intervals to ensure that the product meets the required lead specifications. Once the lead is in specification, it is cast in the required shape and either sold to the market or used internally for production of calcium and antimonial alloys. 

The route shown in Fig. 9.12 is one which has been operated commercially in the U.K. on a fairly small scale, quite successfully. As in the case of niobium, it is convenient to use the crude ferro alloy as feed to the chlorination stage. The chloride purification stages lead to pure vanadium trichloride, which is reduced with magnesium in a manner similar to that employed for titanium, zirconium or hafnium. Some of the complexities, applicable in the latter processes owing to the volatile nature of the chlorides, are absent with vanadium. The vanadium metal sponge has some properties in common with the other metal sponges. 

Mizutani et al. (2003) reported that the anodized coating on Mg alloys formed at 60 V in an alkaline solution contained a mixture of magnesium hydroxide and magnesium oxide which has been confirmed by X-ray diffraction (XRD) analysis. Therefore, the involvement of reaction (16.5) in this stage is reasonable. The reasonability of reactions (16.3), (16.4) and (16.5) involved in this stage of anodizing can also be supported by experimental results. For... 

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