Thermodynamics And Experimental Research On Production Of Mg-Sr Alloy Using Vacuum Silicothermic Reduction

Reduction technologies vacuum production process is relatively simple, good environmental conditions, high purity. It occupied a very important position in non-ferrous metal smelting the area.Vacuum conditions can be an effective way to protect reactive metal become oxidation in the atmosphere, reduction reaction temperature can be reduced. Reduction technologies vacuum is the best way to smelt and purif magnesium, calcium, strontium, etc.Vacuum silicothermic reduction technology have be used to Prepare Mg-Sr alloy creatively In this paper. It is a Thesis of Thermodynamic Analysis and experimental research on Production of Mg-Sr alloy using vacuum silicothermic reduction. The Gibbs free energy and the critical reduction temperature of vacuum silicothermic reduction producing metallic strontium were calculated and analyzed. Chemical reactions were deduced for preparing metal Sr and Mg-Sr alloy. Reactions thermodynamic conditions were obtained. Reaction temperature and vacuum degree have an effect on the reaction process.TG-DSC thermal analysis experiment and thermal vacuum preparation of metal Sr and Mg-Sr alloy experiment were carried out. Metal Sr and Mg-Sr alloy were produced by metal vacuum silicothermic reduction technology.Ssamples of Mg-Sr alloy was obtained. The phase composition of the reaction product and slag was analyzed separately. Microstructure of sample was observed. According to the condensation features of Mg, Sr vapor, designed synchronous condensation technology to achieve the metals of Mg and Sr.Thermodynamic analysis and experiment results show that:1) Under standard atmospheric pressure, the critical reaction temperature for silicon reduction of MgO and SrO is 2429K, 2876K respectively, the critical reaction temperature is high and difficult to implement industry.2) The main reaction for silicothermic reduction for the preparation metal Sr and Mg-Sr Alloy is (1 -x )MgO(s) + xSrO(s) + Si(s) + (1-x)CaO(s) = ( 1-x )Mg (g)+xSr(g) + (1-x)(2CaO·SiO₂ )(s) +x(2SrO·SiO₂)(s),Sr= x mol.% 3) The Gibbs free energy of main reaction at the silicothermic reduction for the preparation Mg-Sr Alloy decreases with temperature increases and pressure reduces.4) Vacuum to 15Pa, heating rate 20℃/min, heating up to 1100℃, insulation 80min, the time was 135min, Mg-Sr alloy thermal silicon can proceed smoothly. Reduction reaction rate is faster in 30-90min, 120min to complete the reaction.5) When the temperature of the condenser Tv <650℃, pressure Pv <267Pa metal metal elements Mg and Sr from high-temperature zone (above the melting point of and Sr) to low-temperature zone (below the melting point of and Sr), metal vapor condense to solid;6) The phase composition of the reaction product and slag were Mg₁₇Sr₂ andα-Mg were formed in the product while Ca₂SiO₄ and Sr₂SiO₄. Mg-Sr alloy crystallization of the condensate is divided into three regions. The size of early condensate is relatively large grains and loose. The size of late condensate is minute grains. Between the former the size of condensate is moderate.