Study On The Equation Of State Of Iron-silicon Alloy In The Earth’s Core Environment

The study of material composition and properties of outer core under high temperature and pressure is of great significance to the formation mechanism of geomagnetic field and other geoscientific topics.However,there are still some disagreements and limitations in the existing research,which are mainly manifested in: 1.There is still no unified understanding of the composition and content of outer core;2.The existing pre-heating impact test technology sample temperature is lower than 1000 K,it is difficult to achieve full coverage of the outer core environment.To solve these problems,based on the first-principles lattice dynamics method,the properties of Fe Si alloys with different compositions in the earth’s core environment are studied,and the pre-heating impact test technology is explored.The specific research methods and progress are as follows:1.Based on the first-principles lattice dynamics method,the thermodynamic properties,elastic properties and equation of state of Fe Si alloys are systematically calculated.Thermodynamic parameters and elastic constants of Fe Si alloys with different silicon content at high temperature and high pressure were obtained,and the elastic properties of Fe Si alloys at high temperature and high pressure were predicted.Based on the elastic constants obtained from the above calculation,the relationship between bulk modulus K,shear modulus G and sound velocity of Fe Si alloy with pressure and temperature is obtained by Hill average approximation.2.For the pre-heating impact loading technology,the temperature of sample is lower than1000 K,so that the impact temperature and pressure are difficult to completely cover the outer core environment interval.This paper explores the technologies of electromagnetic induction heating and sample precision support.In the aspect of electromagnetic induction heating,the parameters and arrangement scheme of the electromagnetic induction coil are determined by the finite element simulation method,so that the sample can be quickly raised to the set temperature(more than 1000 K);in terms of the precise support of the sample,we designed a device that can meet the requirements at 1900 K.3.The shock loading tests of Mo and Fe were carried out by using the sample pre-heating system,in which the maximum initial temperature of Mo reached 1827 K,and the effective shock signal was obtained.In the test of iron,the initial temperature of iron reached 965 K.Based on the above research progress,a new understanding of the influence of silicon content on the properties of materials in the earth’s core environment has been obtained.The breakthrough of pre-heating shock test technology lays a foundation for further experimental study on the composition and properties of materials in the earth’s core environment.