铜/铝搅拌摩擦焊接头界面原子扩散及力学性能模拟

Simulation of interfacial atomic diffusion and mechanical properties ofcopper/aluminum friction stir welded joint

利用搅拌摩擦焊技术连接低熔点的铜与铝,连接过程中铜原子与铝原子在界面的扩散能力影响界面力学性能.采用分子动力学研究搅拌摩擦焊过程中铜/铝界面原子的扩散行为,评价了不同应变速率下界面的力学性能.结果表明:铜原子扩散进入铝晶格的数量远大于铝原子扩散进入铜晶格的数量,原子扩散以最近邻跳跃机制为主,铜原子和铝原子的扩散激活能分别为0.58、0.75 eV.界面过渡层厚度主要受保温温度控制,800 K下的界面为最佳厚度界面;拉伸应变速率为1×10^(10)s^(-1)时,界面抗拉强度最大,达到3.19 GPa.塑性变形在铝侧,而铜侧几乎没有塑性变形,变形过程中发生的位错反应由全位错分解和压杆位错合成,位错能下降,是以肖克莱位错为主要的滑移位错.

The friction stir technique was used to connect copper and aluminum with low melting points.The diffusion ability of copper and aluminum atoms at the interface affects the mechanical properties of the interface.Molecular dynamics was used to study the diffusion behavior of atoms at the Cu/Al interface during friction stir welding,and the mechanical properties of the interface were assessed under different strain rates.The results showed that the quantity of copper atoms diffusing into the aluminum lattice is much larger than that of aluminum atoms diffusing into the copper lattice.The atom diffusion is dominated by the nearest-neighbor hopping mechanism with diffusion activation energies of 0.58,0.75 eV for Cu and Al atoms,respectively.The thickness of the interface transition layer is mainly controlled by the holding temperature with the optimal thickness interface at 800 K.The maximum interfacial tensile strength is 3.19 GPa at the tensile strain rate of 1×10^(10) s^(-1).Plastic deformation primarily occurs within the aluminum side with minimal plastic deformation on the copper side.Dislocation reaction during the deformation process includes the decomposition of perfect dislocation and the formation of stair-rod dislocation.The dislocation energy decreases with the Shockley dislocation being the main slip dislocation.