Molecular Dynamics Simulation Of The Microstructure Of Soft Magnetic Material Fe-Ni-Cr

The soft magnetic properties of soft magnetic materials are closely related to their internal microstructure.The rapid solidification process of liquid Fe-Ni-Cr alloy under different parameters(component,cooling rate,pressure)was simulated by molecular dynamics.Using the average atomic energy,pair distribution function,the largest standard clusters,visualization microstructure characterization methods.The evolution of microstructure and phase change crystallization process of Fe-Ni-Cr have been studied in detail,which enriches the theoretical basis for the research and application of Fe-Ni-Cr materials,and is of great significance for improving its soft magnetic properties.The results show that:Fe_(80-x)Ni_xCr₂₀(x=10,20,…,60,70)with 7 groups of different elemental components during the rapid solidification process under the conditions of cooling rate?=0.1 K/ps and pressure P=0 GPa,all form a crystal structure dominated by fcc.The solidification temperature of Fe_(80-x)Ni_xCr₂₀ liquid-solid phase transition decreases with the decrease of Fe content.When the components at Fe₁₀Ni₇₀Cr₂₀ and Fe₂₀Ni₆₀Cr₂₀,the E-T curve of the system undergoes two consecutive first-order phase transitions during the phase transition,which is related to the evolution of the five-fold twinning structure of hcp.It was found during the rapid solidification of Fe₇₀Ni₁₀Cr₂₀ with 6 groups of different cooling rates?=(0.1K/ps,0.5K/ps,1K/ps,2K/ps,5K/ps,10K/ps),Fe₇₀Ni₁₀Cr₂₀ alloy is a good solid solution at high cooling rate and the three element atoms have no obvious segregation phenomenon,they are homogeneously distributed in space.The amorphous critical cooling rate of Fe₇₀Ni₁₀Cr₂₀ alloy is about 10 K/ps.Although the bcc atom has a higher energy,not energetically favorable,it has a strong ability to form crystals in the initial stage of phase transition crystallization.In addition,the average atomic potential energy of Fe₇₀Ni₁₀Cr₂₀ alloy at the lower cooling rate of0.1 K/ps is higher than the intermediate cooling rate of 0.5 K/ps and 1K/ps,which are closely related to kinetic factors.As the screw dislocation in an fcc crystal,the hcp atoms can be removed by slight slides of the close-packed planes;and whether such slides can take place depends on the distribution of fcc crystal regions.It was simulated Fe₇₀Ni₁₀Cr₂₀ in the rapid solidification process at the cooling rate?=1 K/ps,12 groups of different pressures P=(0 GPa,5 GPa,10 GPa,20 GPa,…,90GPa,100 GPa).The results show that during the rapid solidification of the system at the pressure P=0?40 GPa,only the first-order phase transition from the liquid phase to the fcc phase occurred,and the average potential energy of the liquid phase decreases with the increase of pressure.However,In the process of rapid solidification at the pressure P=50?100 GPa,the system undergoes a secondary phase transition from the liquid phase to the bcc metastable phase and then to the mixed phase of fcc and hcp.The average potential energy of the liquid phase increases with the increase of pressure.