Mechanistic Study Of The Adhesion Characteristics At Liquid-Aluminum/Solid Interface Under The Effect Of Solid Temperature

In China,the aluminum reduction industry is in a period of opportunity where policies are stacked up and the momentum is rising.Hence,it has been urgent issue to reduce the adhesion of high-temperature liquid-Al to the inner walls of aluminum reduction cells and vacuum ladles to improve production efficiency and reduce cost.The effect of substrate temperature on the adhesion of liquid-Al is simulated by using molecular dynamics method targeting the adhesion of liquid-Al/solid Al/Si/SiO₂surface at different temperatures.Firstly,a reasonable liquid/solid model is established.The changes in the center of mass,contact angle,adhesion image,and adhesion force of the liquid-Al are analyzed under the coupling effect of substrate and temperature.Then the adhesion characteristics of the liquid-Al are investigated qualitatively.In particular,the extent of adhesion at the SiO₂ surface is quantitatively investigated by calculating the work of adhesion using“phantom wall”method.Finally,the adhesion mechanism of liquid-Al is explored in depth in terms of the diffusion behavior of atoms,the interfacial potential,and the atomic density.The main points are as follows:（1）The parameters of the molecular dynamics model are optimized to construct a reasonable and accurate adhesion model of temperature/substrate.The melting process of single-crystal Al is simulated.The variation of temperature,crystal volume,kinetic energy and potential energy in the system with time is analyzed.Combining the laws of atomic configuration changes of Al melting,the radial distribution function curves of Al at different temperatures are compared.All of these determined that single-crystal Al had completely melted at 1143 K,creating a solid basis for the subsequent simulation of the liquid-solid interface.（2）The tendency effect of temperature on the adhesion at liquid-Al on solid Al/Si surfaces is described.The contact angle,center of mass,and the adhesion force with the liquid-Al are analyzed during the adhesion process.Then the adhesion forces at the liquid-solid interface are calculated.The diffusion behavior of liquid-Al on the solid surface is investigated.The variations of interfacial potential with temperature are compared.It shows that the number of liquid atoms breaking away from the aggregated state to penetrate into the substrate Al increases as the temperature rises.The thermal excitation effect increases the probability of collision between liquid and solid Al atoms,which intensifies interfacial adhesion of Al-Al system.Conversely,on the Alophobic Si surface,the thermal excitation effect reinforces the aggregation of Al,causing the atoms in contact with the interface to move away from each other,leading to a reduction in interfacial adhesion.It expresses that the adhesion of liquid-Al on the solid Al surface aggravates and the adhesion on the solid Si surface weakens when the temperature increases.（3）The competitive effect of temperature on the adhesion of liquid-Al on the solid SiO₂ surface is presented.The variation of contact angle,and adhesion force with temperature are compared during the adhesion of liquid-Al/solid SiO₂ surfaces.Secondly,the work of adhesion at liquid-Al is calculated using the"phantom wall method".The adhesion mechanism is revealed by combining the substrate atomic density with the distribution of the number of atoms in the adhesion region.In this thesis,the adhesion force is negatively correlated with temperature is expressed systematically.It indicates that increasing the temperature deepens the degree of substrate atomic lattice mismatch,resulting in denser atoms on the surface of the substrate.The liquid-solid atoms squeeze and penetrate each other on the adhesion surface.The consequence of the competition is that the Al atoms are squeezed out of the adhesion interface.Then the number of Al atoms in the adhesion area is reduced,resulting in a weakening of the penetration capacity of the Al liquid atoms.The liquid-solid atomic bonding ability is weakened,which shows a decrease in adhesion with increasing temperature.（4）The degree of adhesion at the liquid-Al on different substrates under the same temperature conditions is discussed.A comprehensive comparison of the changes in contact angle and interfacial potential at the same temperature revealed that there are different degrees when the liquid-Al adheres to different substrates.The degree of adhesion is ranked from strong to weak as Al>SiO₂>Si.In other words,the adhesion between the liquid-Al/solid Al is the most severe,followed by the SiO₂ substrate and the weakest adhesion on the solid Si surface.