Molecular Dynamics Simulation Study On Thermophysical Properties Of Mg-Cu Alloys

Mg-Cu alloy is a new phase change heat storage material,which has the advantages of high thermal conductivity,high energy storage density,and stable performance.It is widely used in medium and high temperature thermal storage system.Research on aluminum-based metal phase change heat storage materials at home and abroad.However,since aluminum-based alloys tend to corrode packaging materials,and magnesium-based materials are much less corrosive than aluminum-based materials,magnesium-based thermal storage materials have advantages for high-temperature thermal storage.There are many limitations to study PCM by experimental methods.Computer simulation methods can break the limitations of traditional experiments.The molecular dynamics simulation is a new method for studying thermal storage materials.It has the advantages of simulating extreme conditions and directly observing atomic changes.At present,few scholars have studied alloy thermal storage materials by this method.In this paper,we used the molecular dynamics method by atomic embedded potential?EAM?.Some block models of Mg crystal,Mg-24Cu alloy,Mg-31Cu alloy and Mg-40Cu alloy were established.The solidification process was studied at a cooling rate of 10¹² K/s by molecular dynamics simulation with NPT ensemble.The pure Mg crystal,Mg-24Cu alloy,Mg-31Cu alloy and Mg-35Cu alloy formed an ordered crystal structure by Ovito.The radial distribution function?RDF?and mean square displacement?MSD?also show the same results.The pair distribution function shows that there is a stronger interaction between different atoms in the Mg-Cu alloy.This interaction is beneficial to the formation of the?-Mg+Mg₂Cu eutectic,which changes the thermophysical properties of the alloy.The thermal properties of seven alloys were studied by molecular dynamics method.According to the energy-temperature curve and the specific heat capacity-temperature curve,the melting point and specific heat of the alloy were studied.With the increase of Cu content,the melting point decreased first and then increases.The melting point of Mg-31Cu alloy was the lowest.When the temperature rised from 300K to 700K,the specific heat of the Mg-Cu alloy increased.When the Cu content increased from 20%to 45%,the specific heat of the Mg-Cu alloy decreased.According to the change curve of energy in the phase change process,the melting enthalpy of the alloy was studied.The melting enthalpy of Mg-Cu alloy increased first and then decreased with the increase of Cu content,and the melting enthalpy of Mg-31Cu alloy was the highest.The thermal conductivity of Mg-Cu alloy was calculated by non-equilibrium molecular dynamics method.The thermal conductivity decreased with the increase of Cu content,but the thermal conductivity was still high.Three different compositions of Mg-Cu alloy were designed and prepared by experimental methods.The composition of the alloy was analyzed by X-ray diffraction?XRD?and electron probe X-ray micro analyzer?EPMA?.The alloy was observed by optical microscope?OM?.Thermophysical properties were tested by differential scanning calorimetry?DSC?.Comparing the simulated and experimental values of the thermal properties of Mg-Cu alloy.The simulated values of the density agreed well with the experimental values.The simulated values of phase transition temperature and phase transition differ greatly from the experimental data,but their trends were consistent;the simulated values of specific heat capacity and thermal conductivity had a acceptable deviation from the experimental value.The conclusion of the radial distribution function is consistent with the EMPA.