Microstructures and thermal properties of Sn-Bi-Pb-Zn alloys as heat storage and transfer materials

Low-melting-point alloy has the characteristics of high thermal conductivity,low solidus temperature and the wide range of use temperature,which is a potential heat transfer medium.The microstructure and thermal properties of Sn-Bi-Pb-Zn alloys as heat transfer and storage material were investigated in this paper.The phase compositions,microstructure and thermal properties were investigated by X-ray diffusion (XRD),electron probe microanalysis (EPMA) and differential scanning calorimeter (DSC) analysis,respectively.The results show that the phases of Sn-Bi-Zn and Sn-Pb-Zn alloys are mainly eutectic formed by solid solution,while the formation of Pb7Bi3 intermetallic compounds decreases the melting point of Sn-Bi-Pb and Bi-Pb-Zn.The thermal properties of the zinc-containing alloys are better than that of Sn-Bi-Pb,but the weight of the zinc-containing alloys significantly reduces above 900 ℃.As the density,specific heat capacity and thermal diffusivity change with temperature and physical state,the thermal conductivity of the alloys first decreases and then increases.These results demonstrate the feasibility of using low-melting alloys as the heat transfer and storage material.

High-temperature corrosion of Sn-Bi-Zn-Ga alloys as heat transfer fluid

The new heat transfer alloy is highly reactive at high temperatures,and the corrosion of the container material determines the service life of the heat transfer system.The high-temperature corrosion of Sn-Bi-Zn-Ga alloys as heat transfer fluid was investigated.The microstructure and elemental distribution were studied by field emission scanning electron microscopy(FESEM)and energy dispersive spectroscopy(EDS).The thermal properties before and after corrosion were studied by differential scanning calorimetry(DSC).The results show that the corrosion kinetics of the studied materials follows the parabolic law and the thermal properties after corrosion are improved.Ga significantly improves the thermal conductivity.316 stainless steel exhibits excellent corrosion resistance due to its high Cr and Ni contents.Corrosion mechanism analysis shows that the oxidation of Ga has a smaller Gibbs free energy,and an oxide forms at the corrosion interface to prevent dissolution corrosion and oxidative corrosion of the container material.