Molecular Dynamics Simulations Of The Diffusion Characteristics On The Fe-w Interfaces System

The energy crisis is one of the most serious problems that the world will face in the future,and the development and use of tritium-deuterium(T-D)fusion energy is considered to be one the most reliable way to solve this problem.Radiation-resistant,low-activity steels are considered ideal first wall materials(PFMs)in future tritium deuterium fusion devices.Tungsten is currently used as a favorable ma terial for plasma-facing components because of it low physical sputtering,low solubility to hydrogen,high melting point and excellent anti-swelling properties.Experimentally,an enriched W layer is expected to form on these steels by preferentially sput tering lighter components,and consequently lower the corrosion and increase their lifetime and reduce pollution from the fusion plasma.However,observation indicates that the interdiffusion of iron and tungsten may offset the enrichment process of W,esp ecially at high temperatures.Although some research has been conducted on iron and tungsten model system,but a comprehensive understanding of the interdiffusion mechanism of iron and tungsten on the interface from a microscopic perspective has not been reported accurately so far and needs to be further explore.In the present work,the Fe-W interface diffusion has been studied based on the Fe-W alloy EAM potential function by using the method of molecular dynamics(MD)simulation calculation.In addition,we also evaluated the effect of the intermediate phase Fe2W found in the Maximilian experiment on the Fe-W interface diffusion.Based on the EAM potential function of Fe-W alloy,the Fe-W interface model has been constructed.The evolution of Fe-W interfacial diffusion with time is studied.And in is found by careful analysis that the longer diffusion time is,the more obvious the interdiffusion is,the more the number of interdiffused atoms is.Through further analysis of the results,we found the interd iffusion process of the Fe-W system is asymmetrical diffusion,and the W atoms are more prone to diffuse into Fe matrix,occupying the dominant direction of diffusion.In addition,the effect of temperature on the diffusion at the Fe-W interface is also studied,which is a crucial factor affecting diffusion.The higher the temperature is,the stronger and faster the atoms vibration is,and the wider the interface width is.Besides,the effect of interfacial orientations is significant and studied,and by co mparative analysis of the interface diffusion at(100),(110)and(111)at 1100K,we found that the(111)plane is more conductive to Fe-W diffusion than(110)and(100)planes.The differences in the surface energy and density are the main causes of the a nisotropy of the interface structure.Finally,the influence of intermediate phase Fe ₂W on the interface diffusion is studied.By constructing an interface model with or without Fe ₂W,the interface widths of the three interfaces Fe(100)-W,W-Fe₂W,and Fe₂W-Fe evolved with time were counted.It is found that the Fe(100)-W interface width is much larger than the W-Fe₂W and Fe₂W-Fe interface widths,which means the intermediate phase Fe ₂W has a negative effect on the interdiffusion of Fe and W,and the progres s will be restricted by the intermediate phase,which indicates that the Fe ₂W is benefit to the enrichment process of W on Fe substrates,hence protecting the Fe substrate in the fusion reactor.