Molecular Dynamics Study Of The Effect Of Liquid Lithium Corrosion On The Mechanical Properties Of α-iron

In the magnetic confinement fusion device,the role of the divertor is to isolate the high-temperature plasma from the vacuum chamber wall and prevent the two from interacting.In recent years,a large number of experiments have proved that liquid lithium has unique advantages when used as the plasma facing material of divertor.It can solve most of the problems faced by solid plasma facing material,which makes the liquid lithium divertor an advanced concept in the field of magnetic confinement fusion.However,liquid lithium has brought severe corrosion problems to most metal materials,and the microstructure changes caused by corrosion will inevitably lead to the degradation of the macroscopic mechanical properties of materials.For structural materials,the degradation of mechanical properties will bring safety risks to the entire device.To reveal the relationship between lithium corrosion and the change of the mechanical properties,molecular dynamics simulations of the dynamic responses of <100>,<110> and <111> orientated single crystal α-iron under uniaxial tensile loading were performed in this paper.The stress-strain curves of the crystal with different lithium concentrations were obtained.The effects of lithium atoms on the plastic deformation behavior and yield stress were analyzed in detail.Results showed that the lithium atoms promoted the formation of dislocations,which significantly suppressed the phase transition from bcc to hcp of <110> orientated crystal.In addition,the lithium atoms enhangced the ductility of <111> orientated single crystal α-Fe,making its failure mode change from brittle failure to ductility failure.Meanwhile,the yield stress of single crystal α-Fe was also significantly affected by lithium atoms,whose magnitude decreased monotonously with the increase of lithium concentration and was affected by the distribution of lithium atoms.Besides,the presence of lithium atoms also changed the relationship between the yield stress of α-Fe and temperature.Furthermore,considering that the solute atoms will interact with the defects in the material,the effect of lithium atoms on the glide performance of 1/2<111>{110} edge dislocation in the single crystal α-iron was investigated by using the molecular dynamics method as well.Results showed that the lithium atoms suppressed the glide of the edge dislocation,resulting in a significant decrease in the glide velocity.The static threshold stress,dynamic threshold stress and drag coefficient of edge dislocation glide all increased linearly with the increase of lithium concentration.The dislocation glide behaviors were also affected by the distribution of lithium atoms and the period width along the dislocation line.Forbidding the existence of lithium clusters and increasing the period width along the dislocation line can promote the edge dislocation glide.In addition,due to the interaction between the edge dislocation and phonons,increasing the temperature will lead the decrease in the glide velocity of the edge dislocation.