(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 中国铝业公司，北京 100082)
摘 要: 利用光学显微镜(OM)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)研究大变形冷轧Al-6Mg-0.4Mn- 0.25Sc-0.1Zr(质量分数，%)合金在不同稳定化退火过程中的组织演变及单轴拉伸断裂行为。结果表明：在大变形冷轧过程中，弥散分布的纳米级Al3(Sc,Zr)粒子阻碍位错运动和晶界迁移，位错密度显著增加。高密度的位错缠结诱发局部不均匀变形，形成大量剪切变形带。冷轧状态下，合金组织分布不均匀，剪切带区域位错密度较大，变形储能较高，在单轴拉应力状态下，合金沿着剪切带方向发生剪切断裂。在稳定化退火过程中，剪切变形带中优先发生形核与晶粒长大。随着稳定化退火温度的不断提高，亚晶发生合并长大，剪切变形组织逐渐消失，合金的断裂行为由剪切断裂转变为混合型韧性断裂。经过高温稳定化退火处理后，部分Al3(Sc,Zr)粒子发生粗化，析出相弥散强化作用减弱，少量粗大粒子转变为裂纹源，合金强度逐渐减弱。
关键字: Al-Mg-Sc-Zr合金; 稳定化退火; 再结晶; Al3(Sc,Zr)粒子; 力学性能
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Aluminum Corporation of China, Beijing 100082, China）
Abstract:The microstructure evolution and uniaxial testing fracture behaviors of Al-6Mg-0.4Mn-0.25Sc-0.1Zr (mass fraction, %) alloys after high strain cold rolling were investigated during annealing treatment by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that the presence of nano-scale Al3(Sc,Zr) particles will increase the dislocation density due to its great pinning effect on migration of dislocations and grain boundaries during cold rolling. These dislocation tangles induce the occurrence of inhomogeneous deformation in local area and promote the formation of shear bands. When loaded with uniaxial tensile stress, the as cold-rolled specimens tend to fracture along shear bands in which the dislocation density, as well as deformed store energy is higher than that in other regions. The nucleation and growth of new grains occur preferentially in shear bands during stabilizing annealing treatment. The annealed specimens perform a hybrid ductile fracture behavior with the coarsening of subgrains and elimination of shear bands when elevating the annealing temperatures. Meanwhile, the precipitation strengthening effect of Al3(Sc,Zr) particles diminishes gradually due to the coarsening of some particles after high-temperature stabilizing annealing. Some over-size particles even turn to be crack initiation and the mechanical properties of alloys decrease.
Key words: Al-Mg-Sc-Zr alloy; stabilizing annealing; recrystallization; Al3(Sc,Zr) particles; mechanical property
