(1. 兰州理工大学 省部共建有色金属先进加工与再利用国家重点实验室，兰州 730050；
2. 兰州理工大学 有色金属合金及加工教育部重点实验室，兰州 730050)
摘 要: 本文研究了Cu含量、重熔温度及等温时间对Mg-7Zn-0.3Mn镁合金半固态组织演变的影响。结果表明：Mg-7Zn-0.3Mn-1Cu合金的铸态组织由白色α-Mg基体和黑色共晶组织(α-Mg+Mg4Zn7+ MgZn2+CuMnZn)组成。在等温热处理过程中，Cu有加速非枝晶颗粒分离和球化的作用，且Cu含量(质量分数)为1.0%时效果最佳；Mg-7Zn-0.3Mn-1Cu镁合金通过适当提高保温温度或延长保温时间，能够得到细小且分布均匀的球状颗粒。然而当保温温度超过585 ℃或保温时间超过20 min时，半固态颗粒则会粗化长大。这种粗化长大现象是在合并长大机制与Ostwald熟化机制共同作用下产生的。在整个等温热处理过程中，半固态组织演变主要经历了初始粗化、组织分离、球化和最后粗化四个阶段。Mg-7Zn-0.3Mn-1Cu镁合金的最佳等温热处理工艺参数为保温温度585 ℃和保温时间20 min，其非枝晶颗粒的平均尺寸、形状因子和固相率分别为38.85 μm、1.39和53.38%。
关键字: Mg-7Zn-0.3Mn-1Cu镁合金；Cu含量；非枝晶组织；演变机理
（1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China;
2. Key Laboratory of Non-ferrous Metal Alloys and Processing, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:The effects of Cu content (0%, 0.5%, 1.0%, 1.5%), remelting temperature and holding time on the evolution of semi-solid non-dendrites of Mg-7Zn-0.3Mn magnesium alloy were studied. The results show that the cast microstructure of the Mg-7Zn-0.3Mn-1Cu alloy is composed of white α-Mg matrix and black eutectic phase (α-Mg+Mg4Zn7+ MgZn2+CuMnZn). And Cu accelerated the separation and spheroidization of non-dendritic particles during isothermal heat treatment, and the effect is optimal when the Cu content (mass fraction) is 1.0%. By properly raising the holding temperature or extending the holding time, Mg-7Zn-0.3Mn-1Cu can obtain finer and more uniform spherical particles. However, when the holding temperature exceeds 585 ℃ or the holding time exceeds 20 min, semi-solid particles will gradually coarsene. This coarsening growth phenomenon is generated by the combined growth mechanism and Ostwald maturation mechanism. During the whole isothermal heat treatment process, the semi-solid microstructure evolution mainly experiences four stages: initial coarsening, tissue separation, spheroidization and final coarsening. The best parameters of isothermal heat treatment of Mg-7Zn-0.3Mn-1Cu are 585 ℃ in holding temperature, 20 min in holding time, and the average particle size, shape factor and solid fraction are 38.85 μm, 1.39 and 53.38%, respectively.
Key words: Mg-7Zn-0.3Mn-1Cu magnesium alloy; Cu content; non-dendritic microstructure; evolution mechanism
