Atomic Scale Simulation Of The Phase Transition And Interface Properties Of Tungsten-copper Alloy

Tungsten copper(W-Cu)alloy has excellent thermal,electrical,and mechanical properties,making it an ideal structural and functional material.It has been widely used in civil industry,aerospace,national defense and military fields.In existing research,reports on W-Cu alloys mostly focus on alloy preparation,component structure,application performance,and other technological aspects.There is a lack of research on the basic theoretical aspects of atomic interactions,phase transformation mechanisms,grain boundary structure,dislocation motion,and other aspects of W-Cu systems.Therefore,this paper aims to build a new and reliable W-Cu binary potential,systematically study the phase stability,thermal,mechanical properties,solid phase transformation and other physical properties of W-Cu alloy system through molecular dynamics simulation,and on this basis,study the atomic structure,energy,mechanical properties,dislocation movement,crack growth,radiation resistance and other material behaviors of W and W-Cu solid solution grain boundaries and W/Cu interface.The main results of the paper provide important theoretical basis for the development and application of new high-performance W-Cu alloys.The main research results are as follows:Based on the Embedded Atom Method(EAM),new W-W,Cu-Cu element potential and W-Cu binary EAM potential were constructed.Compared with the W-Cu potential reported in the literature,the newly constructed potential can more accurately reflect the energy difference of cohesive energy between the BCC and FCC structures of W and Cu,as well as the phase stability,lattice constants,and mechanical properties of W-Cu solid solution.It is also in good agreement with the experimental and other calculated values reported in the literature,which confirms the reliability of the newly constructed W-Cu binary EAM potential.Through compression and shear deformation simulation of pure W and W-Cu solid solution,it is found that the BCC-FCC phase transformation of W has two different mechanisms,namely,the BCC-FCC phase transformation of W occurs through the Bain path under compression deformation,and the BCC-FCC phase transformation occurs through the Nishiyama Wassermann(NW)path under shear deformation.The addition of Cu will hinder Bain transformation,but promote NW transformation.In addition,the paper found that the slip of aBCC/6<011>BCC and aBCC/6<0(?)>BCC screw dislocations in the BCC phase caused the nucleation and growth of the FCC phase during the NW path phase transition,revealing the atomic scale evolution process of the NW phase transition of W.Symmetric tilt grain boundaries with[100],[110],and[111]tilt axes of pure W and W-Cu solid solution were constructed respectively,and the effect of Cu solid solution content on grain boundary energy of W-Cu solid solution grain boundary was studied.Through Monte Carlo(MC)simulation,W100-xCux grain boundaries were constructed by replacing W atoms near pure W grain boundaries with Cu atoms,and their mechanical properties,crack propagation at grain boundaries,and radiation resistance were studied.The results show that as the number of Cu atoms increases,the tensile strength of grain boundaries decreases and the brittleness increases.The doping of Cu atoms is beneficial for the propagation of grain boundary cracks,and the higher the content of Cu atoms,the faster the crack propagation speed.The presence of Cu impurity atoms will have a significant impact on the number of defects at W grain boundaries after irradiation.Asymmetric tilt interfaces of W/Cu were studied and it is found that the W(110)/Cu((?)1(?))-KS and W(110)/Cu((?)1(?))-NW interfaces have lower interface energies and higher strength compared to other oriented W/Cu interfaces studied in this work.Furthermore,the formation of W/Cu interfaces plays a crucial role in enhancing the tensile strength of Cu under tensile load parallel to the interface direction due to the hindrance of dislocation motion by the interface.On the contrary,the tensile strength of W/Cu interfaces along the direction perpendicular to the interface is lower than the tensile strength of Cu,likely due to weaker interfacial bonding.