Cu/Al爆炸冲击界面连接及拉伸与切削性能的分子动力学模拟

基于分子动力学方法,从微观角度揭示Cu/Al焊接点处的瞬时爆炸焊接过程,研究纳米焊接件接头处的力学特性及切削加工性能。结果表明:铝、铜板互相碰撞后动能转化为内能,异种原子间互相熔合渗透形成接头;焊接件拉伸时弹性模量介于单晶铝和单晶铜之间,抗拉强度为6.89 GPa,这一值大于宏观实验结果,但所对应的应变率10.67%与实验中的11%接近;在接头区域附近,位错与无序晶格的相互作用造成了塑性变形阶段的应力强化,使得拉伸应力值大于两种单晶;这一强化机制也体现在刀具切削接头区域时的平均切削力大于单晶铜、铝的平均值,与实验结果相一致;无序晶格区严重的位错形核有利于位错产生且沿与切削方向呈45°传播,传播时的塞积导致切削加工硬化效应。

Molecular Dynamics Simulation Connections and Mechanical Properties of Cu/Al Explosion Shock Interface

Based on the molecular dynamics (MD)method,transient explosive welding process of Cu/Al junction point was revealed from the microscopic aspect,and mechanical properties and machinability of the Cu/Al nano-weldment were studied.The results show that kinetic energy is converted into internal energy in the system after the collision.The heterogeneous atoms penetrate into each other and the diffusion effect of copper atoms is better than aluminium atoms.The elastic modulus of the nano-weldment is 64.56 GPa, which is between copper's and aluminium's;however,its yield strength is less than those of the two monocrystals.Interactions between dislocations and disordered lattices cause the stress strengthening in the plastic deformation stage,which causes that the stress values of the weldment is larger than those of the two monocrystals.This strengthening mechanism is also reflected in the cutting process,and the weldment has the highest average cutting force 117.80 nN.A mass of dislocations nucleate in the disordered lattice areas of the weld-ment,and they spread at 45°to the cutting direction.However,dislocations pile up when their propagation is hindered by the disorder-ed lattices and interface,which leads to the work hardening effect.