Rapid Solidification Simulation And Microstructure Analysis Of FeCuNi Alloys

FeCuNi alloy as an Fe-based soft magnetic alloy has important application value in the field of electronic power.However,there is currently no effective physical model to guide the development of FeCuNi alloys with excellent soft magnetic properties.Therefore,the study on the microstructure evolution and glass formation of FeCuNi alloys has far-reaching significance for improving its soft magnetic properties.Based on molecular dynamics simulation,the microstructure evolution of different Fe₇₀Cu_?30-x?Ni_x?x=0,5,10,15,20,30?alloys during rapid solidification at the cooling rate of 10¹²K/s was studied;the evolution of medium-range order in FeCuNi alloys during rapid solidification was studied;the inheritability characteristics of TCP LSCs in FeCuNi alloys during rapid solidification was studied.The simulation results were analyzed by atomic average energy,the coordination number?CN?,pair distribution function,the common neighbor sub-cluster?CNS?,the largest standard cluster analysis?LSC?,the topologically closed-packed cluster?TCP LSC?and 3D visualization techniques.The study of microstructure evolution during rapid solidification of FeCuNi alloys shows that at the cooling rate of 10¹²K/s,all alloys examined here are vitrified overall,even if partially crystallized in Fe₇₀Cu₃₀ alloy.The addition of Ni atoms improves the thermal stability,glass transition temperature T_g,and the number of TCP LSCs in the alloy,thus improving the glass-forming ability of FeCuNi alloys.In addition,the introduction of the structure entropy concept can clearly reveal the critical changes of microstructure near the glass transition temperature.The addition of Ni atoms has complex and stuble effects on the species of CN,CNS,LSC,and their corresponding structure entropy,but all of them have key changes near the T_g.So the structure entropy is a well-defined parameter for microstructure characterization of disordered systems.The study on the evolution of medium-range order during rapid solidification in FeCuNi alloys shows that the ICO LSCs can not be responsible for the second peak split of the total PDF,and TCP LSC is the structural origin of the second peak split,for FeCuNi metallic glasses with the small gap in atomic radii.Furthermore,the study based on the element-type atom pairs in the alloys can not explain the split of second peak in the total PDF.The same conclusions can be obtained in Ni Zr Mo metallic glasses with the large gap in atomic radii.The effect of Ni atoms on the microstructure of TCP LSCs is subtle and complex.Topological invariance is an essential feature of TCP LSCs.In a word,the study of TCP LSCs provides a new way to reveal the basic characteristics of metallic glasses.The study on the heritability ratio of all atoms in TCP LSCs during the rapid solidification in FeCuNi alloys shows that the heritability ratio of central atoms in TCP LSCs first increases and then remains invariant with the decrease of temperature.The heritability ratio of all atoms in TCP LSCs increases with the increase of Ni atoms.The heritability ratio and its variation trend of TCP atoms in FeCuNi alloys,is determined by the trend of TCP atoms number with temperature during rapid solidification.The less the number of TCP atoms formed by metal melt or alloy melt in the supercooled liquid,the lower the heritability ratio of TCP atoms.The more TCP atoms in the TCP LSCs will frequently change to non-TCP atoms during the cooling process,the more complicated the structural evolution of TCP LSCs.In conclusion,for FeCuNi alloys,the increase of Ni atoms not only improves the formation ability of TCP LSCs,but also reduces the complexity of microstructure evolution.