(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: 研究等温热处理温度和保温时间对ZC61-0.3Cr镁合金半固态组织演变的影响。结果表明：在等温热处理过程中，ZC61-0.3Cr合金中的原始树枝晶组织能够转变为半固态非枝晶组织，得到均匀、圆整的球状颗粒。随着保温温度的升高，合金中的原始树枝晶组织经过初始粗化、组织分离和球化演变成半固态非枝晶组织；随着保温时间的延长，晶界处的(α-Mg+MgZn2+CuMgZn)共晶组织优先熔化，合金中的大块状组织逐渐演变为球状组织；但是，保温温度过高或保温时间过长，都会引起球状颗粒的粗化长大。在粗化长大过程中，合并长大机制和Ostwald熟化机制同时存在，共同影响固相颗粒的形貌和尺寸大小。ZC61-0.3Cr镁合金半固态成形所需的最佳工艺条件为(585 ℃, 30 min)；此条件下，其颗粒平均尺寸、形状因子和固相率分别为43 μm、1.4和51%。
关键字: ZC61-0.3Cr镁合金；半固态等温热处理；非枝晶组织；组织演变
（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 the isothermal heat-treatment temperature and holding time on semi-solid microstructural evolution of ZC61-0.3Cr magnesium alloy were investigated. The results indicate that the original dendritic microstructure in ZC61-0.3Cr alloy can be transformed into semi-solid non-dendritic microstructure and can obtain uniform and round spherical particles during the isothermal heat-treatment. With the increase of holding time, the eutectic microstructure (α-Mg+MgZn2+CuMgZn) at the grain boundaries is melted preferentially, the original dendritic microstructure in the alloy is turned into semi-solid non-dendritic microstructure by initial coarsening, microstructure separation and spheroidizing. As the holding time increases, the microstructure of alloy gradually changes from large block to spherality. However, the coarsening and growth of spherical particles would cause, when the holding temperature is too high or the holding time is too long. In the process of coarsening and growth, the mechanism of combining growth and Ostwald ripening coexist and together affect morphology and size of the solid phase particles. The optimum process condition for semi-solid forming of ZC61-0.3Cr magnesium alloy is (585 ℃, 30 min). Under this condition, the average particle size, shape factor and solid fraction are 43 μm, 1.4 and 51%, respectively.
Key words: ZC61-0.3Cr magnesium alloy; semi-solid isothermal heat treatment; non-dendritic microstructure; microstructural evolution
