Calculation Of The Structural Short-range Forces——Disjoining Potential In The Premelted Al-Pb Solid-liquid Interface

Liquid metal brittleness,thermal cracking,and other material failure behaviors are very common in industrial production.There are many reasons for such behaviors,but the most fundamental reason is that there is an interaction,that is,short-range structure interaction potential-disjoining potential.Disjoining potential is the interaction between two interfaces on a microscopic scale.In-depth understanding and measurement of the important thermodynamic function of the disjoining potential will have important significance for the adjustment of the micro-interface structure and thermodynamic properties of the alloy,and also provide basic data for the genome engineering of the material interface.So far,the research on the disjoining potential has mainly focused on the metal surface premelting and grain boundary premelting systems,but there is still little research on the disjoining potential under the solid-liquid interface pre-melting system.In addition,existing studies have shown that grain boundary orientation and alloy concentration also have an effect on the form of disjoining potential.However,studies on the disjoining potential under different grain boundary orientations using alloy systems are still lacking.Based on the above background,this paper studies the disjoining potential between the homogeneous solid-liquid interface and the heterogeneous liquid-liquid interface in the Al-Pb alloy solid-liquid interface premelting system.The molecular dynamics simulation method is used to establish the Al-Pb system.Three different crystallographic directions(100),(110),(111)were simulated,and nine different sets of temperatures were simulated.The analysis and calculation of the disjoining potential were performed by Fensin et al.[Phys.Rev.E,81:031601(2010)] who proposed the histogram sampling method.In this study,this method is extended to the heterogeneous solid-liquid interface premelting system.The thickness fluctuations of the premelted aluminum film at different temperatures are counted to obtain premelting at different temperature equilibrium states.The probability density of the liquid film thickness is used toextract the relationship between the disjoining potential function and the liquid film thickness.The conclusions obtained are as follows:(1)The results of the three crystallographic directions in the single exponential decay form of the disjoining potential are compared,and it is found that the decay length of the disjoining potential is between 1.3-1.5 ?,and Yang et al.[Phys.Rev.Lett,110:096102(2013)] who predicted the disjoining potential results under this system by the complete premelting theory are compared with the method,and the two results are found to be very close as a whole,and there are very different methods in this study.The method used has greater advantages in the use of liquid film thickness fluctuation data and the selection of the form of disjoining potential,which can provide more help for the later study of the disjoining potential in more complex alloy systems.(2)The theoretical study of the disjoining potential shows that the disjoining potential comes from the density wave mismatch.Inspired by this study,this work studies the density distribution of aluminum atoms in the solid-liquid interface and the liquid-liquid interface of the system at the melting temperature.It is found that the decay length of the solid-liquid interface is greater than that of the liquid-liquid interface.Compared with the two decay lengths in the double exponential decay form of the disjoining potential,it is found that the contribution of the exponential term with a large decay length in the double exponential function form comes from aluminum-lead solid-liquid interface,the contribution of the exponential term with small attenuation length comes from the aluminum-lead liquid-liquid interface.