Research On Thermal Conductivity Of Magnesium Alloy Based On First Principles

Magnesium alloys have the characteristics of light weight,high strength,high thermal conductivity,etc.,and is widely used in the fields of electronic communication and aerospace.The traditional method for characterizing the thermal conductivity of magnesium alloys is to test the density,specific heat capacity and thermal diffusivity of the material,and then multiply to obtain the alloy thermal conductivity.But this method consumes a lot of resources,and takes a long time.In order to further improve the efficiency of the thermal conductivity characterization of magnesium alloy materials,this study proposes the application of first principles combined with the alloy heat conduction structure model to characterize the thermal conductivity of magnesium alloys.Introducing constant relaxation time approximation,applying DFT and MLWFs methods to solve the electronic thermal conductivity of metals and second-phase materials,simplifying the calculation process of electronic thermal conductivity;When calculating the phonon thermal conductivity,the Birch-Murnaghan equation of state and the Debye model are introduced into the Slack equation,which improves the calculation efficiency of the phonon thermal conductivity.This method is used to calculate the electrical conductivity and thermal conductivity of the metal and the second-phase material in the temperature range of 300-700 K.The calculated value is in good agreement with the measured value,which verifies the accuracy of the calculation method.The calculation results show that electrons are always the most effective carriers in the heat transport process of the metal and its second phase,and as the temperature rises,the proportion of electron thermal conductivity gradually increases.At the same time,the analysis results verify the validity of Weidmann-Franz law in the temperature range of 300 to 700 K.For the calculation of the thermal conductivity of magnesium alloys,the subject proposes a method combining first-principles calculations with the alloy thermal conductivity structure model.The thermal conductivity of four alloys of magnesium-aluminum,magnesium-zinc,magnesium-yttrium,and magnesium-calcium was calculated by this method,and the calculation results were compared with experimental measurements to verify the accuracy of the method.The calculation results of alloy thermal conductivity show that the calculation method of alloy thermal conductivity proposed in this topic has higher accuracy for alloy materials with low solid solubility.For alloys with high solid solubility,it is necessary to strictly consider the influence of solid solution atoms on the thermal conductivity of the matrix material.