| The thermal storage technology is the key technology of solar thermal powergeneration system. Phase change thermal storage technique can solve the conflictbetween time and space, it can effectively increase the energy utilization efficiency.The alloy phase change thermal storage material has broad application prospects inthe field of solar energy heat utilization thermal storage technology, it has theseadvantages, such as high thermal storage density, high thermal conductivity, stableperformance and long service life. At present, the research of Al-based alloy phasechange thermal storage material is relatively mature at home and abroad, but forMg-based alloy phase change thermal storage material research is rare.This article designed six kinds of Mg-Cu-Zn-Al-Si alloys in which the content ofMg, Cu, Zn, Al and Si are different, in order to meet the performance requirement ofhigh temperature phase change thermal storage material used in solar thermal powergeneration system, the phase change temperature is between450~650℃range. Thethermal performance such as microstructure, mass density, thermal expansion, phasechange temperature, latent heat, and so on were analyzed, and the influencemechanism of the alloy microstructure and thermal performance was researched.310S stainless steel and304stainless steel were selected for container material, thehigh temperature corrosion of Mg-25Cu-15Zn-8Al-6Si alloy material on the containermaterial was researched.The phase constitution of the alloy materials was studied with X-ray analysistechniques, combining phase constitution and metallographic micrograph, alloymicrostructure was analyzed, the results show that the microstructure ofMg-Cu-Zn-Al alloy is mainly composed of α-(Mg), MgZn, CuMg2, CuAl2, MgCuAl2,and it also indicates that the volume of MgCuAl2is increased and the volume ofCuAl2is reduced along with the content of Al increasing; when the element of Siadded, Mg2Si phase formed in alloy. The mass density of the alloy materials wasmeasured with hydrostatic method, through the research, the mass density ofMg-Cu-Zn-Al alloy increases with the content of Al increasing, and that also demonstrates that the mass density of Mg-Cu-Zn-Al-Si alloy increases with thecontent of Si increasing. The linear expansion coefficient of alloy materials wasstudied by thermal expansion instrument, through this research, it shows that theaverage linear expansion coefficients of alloy materials are in2.9214×10-5~3.1707×10-5K-1range, within the temperature of alloy materials rangefrom40℃to440℃, it also draws the rule that the higher the content of Al and Si inthe alloy, the smaller the average linear expansion coefficient. The phase changetemperature and latent heat were studied through differential scanning calorimetricanalysis, the results show that all the phase change temperature of alloy materials is in450~650℃range, those conclusions also show that the latent heat value of alloymaterials is higher than200J/g, the results indicate that the thermal storageperformance of alloy materials meet the requirement of solar thermal utilization hightemperature thermal storage system.The corrosion extent of310S stainless steel and304stainless steel in meltingMg-25Cu-15Zn-8Al-6Si alloy material have reached saturation after277hours. Thecorrosion layer thickness of304stainless steel (0.122mm) is21.3%lower than310Sstainless steel (0.155mm), the corrosion rate of310S stainless steel is4.47μg·mm-2h-1,but which of304stainless steel is3.49μg·mm-2h-1, in conclusion, compared with the310S stainless steel,304stainless steel has a better corrosion resistance to meltingMg-based alloy,304stainless steel is the best choice for Mg-Cu-Zn-Al-Si alloycontainer materials.Through this research, the Mg-Cu-Zn-Al-Si alloy phase change material has alarge advantage in the aspects of thermal storage property and corrosivity, and theexperimental study provides theory and experiment support for its application in thefield of phase change thermal storage technique. |
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