Molecular-Dynamics Simulation Study On The Surface Segregation Of Alloys

Surface science is a subject which is rapidly developed during recent years, and its main domain includes surfaces and related processes. Lately, surface science has started to realize and explain the atom arrays, chemical compositions, moving states of surfaces. One hot issue of the surface science is surface segregations in alloys. Surface segregation can powerful influence the catalysis, oxidation and corrosion in surface of alloys. Its well understanding will strongly assist materials to improve their physical and chemical properties. It also has important significance to actual application.In this paper, the process of temperature increasing and temperature decreasing of alloys are investigated using micro canonical ensemble of molecular dynamics in combination with embedded atom potentials. We study the surface segregation in different alloys and the difference between anneal and quench.Our simulation results mainly include:(1) In the binary alloy FeNi19, it is observed that Fe strongly segregates to the surface layer, while Ni is poor in this layer; there is no obvious segregation in the second layer and lower layers. Different descend-temperature speed: anneal and quench bring a little difference in surface segregation.(2) In the binary alloy FeCo9, Fe strongly segregates to the surface layer and segregation to the second layer with less intensity; Co is poor in the surface layer and the second layer. Relative to quench, anneal bring an obvious segregation in surface.(3) In the binary alloy FeMo5, it is observed that Fe segregates to the surface layer, while Mo segregates to the second layer. Relative to quench, anneal bring an obvious segregation in surface.(4) In the ternary alloy FeNi19Co9, Ni is poor in this layer, Mo is thorough disappear in the surface layer; and no segregation observed in the second and lower layers. Relative to quench, anneal make less Ni stay in the surface layer, while have no influence in Co's segregation.(5) In the ternary alloy FeCo9Mo5, Co segregates to the surface layer, and represent no segregation in the second and lower layers; Mo have no segregation in all atom layers. Relative to quench, anneal make Co have a higher intensity segregation in the surface layer, and make no obvious influence in Mo's segregation.(6) In the multiple alloy FeNi19Co9Mo5, Ni is poor in the surface layer; Co have no segregation in all atom layers, Mo is not appear in the surface layer, while segregates to the second layer. Different descend-temperature speed: anneal and quench bring a little difference in surface segregation.The results above are still no seen reported about other alloys'surface segregation except (1)(2). Though the simulation results need to be illustrated, they still have some certain directive significance, and will be helpful to go deeper to understanding the surface properties of alloys.