Molecular Dynamics Simulation Of Diffusion For Ni-Zr And Ni-Al

Ni-Zr and Ni-Al have been extensively studied due to their excellent high temperature mechanical properties and resistance to radiation and corrosion.The excellent properties of Ni-Al and Ni-Zr alloys benefit from their wide variety of intermetallic compounds,and diffusion has a great influence on the formation of their intermetallic compounds.In this paper,the diffusion behavior of Ni-Zr and Ni-Al systems was studied by molecular dynamics simulation.The main contents are as follows:First of all,the molecular dynamics has been applied to study the effects of temperature on interdiffusion of Ni-Zr.The simulated results indicate that the thickness of Ni/Zr diffusion layer increases with diffusion time and the diffusion zone is characterized as amorphous state.During the diffusion process,Ni atoms diffuse more easily and deeper into Zr side than Zr atoms into Ni side.The diffusion activation energies of Ni and Zr crossing the interface are,respectively,1.33 and 1.42 eV for Ni(100)//Zr(0001),1.25 and 1.28 eV for Ni(110)//Zr(0001),at the temperature range of 950-1100 K.Three possible microscopic diffusion mechanisms for Ni atoms in Zr lattice have been considered and the most possible diffusion mechanism is the interstitial hopping mechanism,as for Zr in Ni,the vacancy diffusion mechanism is favored.The interdiffusion for case of Ni(110)//Zr(0001)is more easily than for that of Ni(100)//Zr(0001).In the diffusion zone of Ni-Zr,some typical clusters existed in Ni-Zr intermetallic compounds have been identified,which are generally consistent with the experimental observations in diffusion couples.The molecular dynamics has been applied to study the effects of temperature on interdiffusion of Ni-AI.The simulated results indicate that the thickness of Ni/Al diffusion layer increases with diffusion time.During the diffusion process,Ni atoms diffuse more easily and deeper into Al side than Al atoms into Ni side.The total activation energy energies of Ni and Al are,respectively,0.915 and 0.69 eV for Ni(100)//Al(lll),0.612 and 1.08 eV for Ni(lll)//Al(lll),at the temperature range of 650-800 K.Three possible microscopic diffusion mechanisms for Ni atoms in Al lattice have been considered and the most possible diffusion mechanism is the vacancy diffusion mechanism,as for Al in Ni,the vacancy diffusion mechanism is favored.The interdiffusion for case of Ni(100)//Al(lll)is more easily than for that of Ni(lll)//Al(lll).In the diffusion zone of Ni-Al,some typical clusters existed in Ni-Al intermetallic compounds have been identified,which are generally consistent with the experimental observations in diffusion couples.