(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: 采用等温热处理工艺研究了保温温度以及保温时间对ADC2-0.4Mg-0.9Cu合金半固态组织演变的影响。结果表明：等温热处理使得铸态合金中的不规则树枝晶组织转变为球状或近球状的非枝晶组织。适当地提高保温温度或延长保温时间有利于ADC2-0.4Mg-0.9Cu合金非枝晶组织的分离与球化，但保温温度超过610 ℃或在较高温度下保温时间超过15 min后，非枝晶组织易发生粗化，这种现象是由合并长大机制和Ostwald熟化机制共同作用导致的。ADC2-0.4Mg-0.9Cu合金整个半固态组织演变过程中，经历了枝晶粗化、分离与球化以及熟化粗化三个阶段；最佳等温热处理工艺为：610 ℃保温15 min，此时非枝晶平均晶粒尺寸、固相率和形状因子分别为50.162 μm、42.75%和1.671。
关键字: ADC2-0.4Mg-0.9Cu合金；非枝晶态组织；等温热处理；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 Nonferrous Metal Alloys and Processing, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:The effects of secondary heating temperature and holding time on microstructure evolution of semi-solid ADC2-0.4Mg-0.9Cu aluminum alloy were studied by using semi-solid isothermal heat treatment process. The results show that the amorphous dendritic structure of the alloy transforms into spherical and near-spherical non-dendritic structure by isothermal heat treatment. It is beneficial to increase the holding temperature or prolong the holding time properly for the separation and spheroidization of ADC2-0.4Mg-0.9Cu alloy. However, when the holding temperature exceeds 610 ℃ or the holding time exceeds 15 min, the non-dendritic tissues are prone to coarsening, which is caused by the combined growth mechanism and Ostwald maturation mechanism. The semi-solid microstructure evolution of ADC2-0.4Mg-0.9Cu aluminum alloy undergoes three processes: dendrite coarsening, separation, spheroidization and finally ripening coarsening. The average grain size, solid fraction and shape factor of non-dendrites are 50.162 μm, 42.75% and 1.671, respectively, under the optimal isothermal treatment at 610 ℃ for 15 min.
Key words: ADC2-0.4Mg-0.9Cu aluminum alloy; nondendritic structure; isothermal heat treatment; evolution mechanism
