Dynamic Simulation Of Atomic Diffusion And Evolution Mechanism Of Defects In Linear Friction Welding

Linear friction welding (LFW) is an efficient solid-phase joining method. It has broad application prospects in the manufacture of blisk. accompanies the interactions of heat, force and metallurgy. LFW is a complex process whick accompanies the interactions of heat, force and metallurgy. Many experiments have been carried out on LFW, while some physical phenomenon and mechanism is difficult to analyse directly by experiment method. Many physical phenomenon and mechanism is supposed to be investigated at the micro-scale. Some numerical simulations have also been carried out in the investigation of LFW, most of which focused on continuum. However, some physical processes in LFW, such as atom diffusion, are discrete. So atomic simulation of linear friction welding is very necessary.In our study, molecular dynamics method is applied to simulate the process of linear friction welding at atomic level. The Ni-Al atomic model of LFW is established, including friction stage and forging stage.The effects of process parameter on LFW are also investigated. The results show that the increase of friction velocity and forging force have a promoted function to the thickness of diffusion layer. Friction velocity mainly affects the diffusion layer produced in friction stage, while forging force mainly influence the diffusion layer generated in forging period.Effects of surface roughness in LFW are investigated based on the atomic model. Simulation results show that rough surface gradually disappeared in friction period. Rough surface of harder material can influence the structure of weld while rough surface of softer material may not influence the weld. We can conclude the whole process of LFW according to the simulation results. First, two sides get closed and contact with each other. Forging force and friction force are both exerted during friction stage. Deformation of softer material occurs so that the contact area of the two sides can increase. Then deformation of the softer material get larger until the two sides reach intimate contact. Last, forging force is exerted to complete welding process.Besides, rules of pore closure in LFW are also investigated. We set pores in the initial configuration. In order to take the effects of diffusion layer near the interface on pores into consideration. We set pore near the interface and far away from the interface respectively. Pores near the interface can get closed during LFW. Pores in Al side get closed in friction stage and Pores in Ni side get closed during forging period. When pores are far away from interface, pore closure in Al slab occurs in forging stage while pores in Ni slab can not get closed.At last, we established finite element model of linear friction welding. Method of multiscale simulation of LFW is presented. Bridge scaling method will be applied to combine molecular dynamics method and finite element method, which provides a potential way to complete the whole simulation of linear friction welding.