采用分子动力学模拟浇铸三层膜铜/铝/铜循环载荷下的孔洞演化

Void evolution of casting Cu/Al/Cu three-layer film by molecular dynamics simulation under cyclic loading

采用分子动力学模拟浇铸法制备的铜/铝/铜三层膜在循环载荷作用下的变形过程,分析孔洞的演化机理。结果表明:铝薄膜的中部和界面处靠近铝侧出现孔洞。铝薄膜中部的孔洞演化为:压杆位错被克服,出现空隙;形核处新产生的压杆位错被克服,空隙长大。数次发射位错环,空位团长大形成孔洞;孔洞形核附近退孪晶形成层错,应力释放,孔洞长大;应力集中、释放使得层错消失、出现,孔洞进一步长大;孔洞形核附近的层错发生交截,且在形核处发射位错,使得孔洞长到最大。压缩力下,孔洞被无序结构原子填充,沿应变加载方向缩小。无序结构原子填充孔洞,孔洞闭合。界面处靠近铝侧孔洞的演化为:压杆位错被克服,出现空隙。应变增加,HCP结构的原子转换为无序结构的原子,空隙沿应变加载方向长大,形成孔洞。随着加载的进行,层错出现,应力释放,孔洞随之增大。随着应变的继续增加,孔洞沿应变加载方向缩小,无序结构原子填充孔洞;周围无序结构原子转化为FCC结构原子,孔洞闭合。

The molecular dynamics method was used to simulate the deformation process of the Cu/Al/Cu three-layer film prepared by the casting method under cyclic loading,the evolution process of void was analyzed.The results show that the voids appear at the middle of the Al film and the interface near the Al film side.The evolution process of the void at the middle of the Al film is as follows:the Hirth dislocation and Stair-rod dislocation at the middle of the Al film are overcome,allowing the gaps to grow.Then,launching the dislocation loop several times at the void nucleation,the vacancy group grows and forms the void.Detwinning crystal forms a stacking fault,releasing the stress and allowing the void to grow.The stress concentration and release make the stacking fault disappear and reappear,and then,the void further grows.The stacking faults near the void nucleation are intercepted,and the dislocation are emitted at the void nucleation,and the void grows to the maximum.Under the compressive force,the void is filled by atoms with other structure,which shrinks into a vacancy cluster along the strain loading direction.The void is filled by atoms with other structure,and closes.The evolution process of the void near the Al side at the interface is as follows:Hirth dislocations and Stair-rod dislocations are overcome,and a gap appears.As strain increases,the atoms of the HCP structure at the nucleation of the void are converted to the atoms with the other structure,and the gap grows along the strain loading direction to form the void.The stacking faults appear,the stress is released,and the void grows with strain loading.Continue to load,and the void shrinks into vacant cluster along the strain loading direction,and the atoms of other structure fill the void.The atoms of other structure around the void are converted to atoms of FCC structure,so void closes.