(1. 清华大学 材料学院，北京 100084；
2. 清华大学 先进成形制造教育部重点实验室，北京 100084；
3. 中国商飞上海飞机制造有限公司复合材料中心，上海 201324；
4. 北京科技大学 钢铁共性技术协同创新中心，北京 100083；
5. 上海航天精密机械研究所，上海 201600)
摘 要: 建立了可控冷却速率的实验方法、凝固过程测温方案和合金内部温度推算方法，对Mg-6Gd-3Y-0.5Zr(质量分数，%)(GW63K)合金开展可控冷却速率实验，结合X射线断层扫描技术、扫描电子显微镜和X射线能谱分析等实验表征手段，表征可控冷速镁合金的凝固组织形貌并获取定量信息，研究了冷却速率对GW63K合金凝固组织微观形貌、定量信息的影响和变化规律。结果表明：在GW63K合金凝固组织中，共晶呈网络状分布在晶界处，形状不规则的第二相呈岛状分布在共晶组织中；平均冷却速率Rc在0.13~0.33 ℃/s范围内，随着冷却速率的增加，网状共晶组织更密集、均匀和连续，第二相分布更均匀、尺寸更小，微观溶质偏析减小，第二相和共晶体积分数均呈下降趋势。
关键字: Mg-Gd-Y-Zr；可控冷却速率；X射线断层扫描技术
（1. School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China;
2. Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Tsinghua University, Beijing 100084, China;
3. COMAC Shanghai Aircraft Manufacturing Co., Ltd., Composites Center, Shanghai 201324, China;
4. Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China;
5. Shanghai Spaceflight Precision Machinery Institute, Shanghai 201600, China）
Abstract:An experimental method of preparing Mg-Gd-Y-Zr alloy solidified at controlled cooling rate, acquiring temperature-time data during the solidification process, and calculating the temperature inside the alloy was established. The experiments were carried out on Mg-6Gd-3Y-0.5Zr (mass fraction, %) (GW63K) alloys, and several GW63K alloy specimens cooled at different rates in the range of 0.13-0.33 ℃/s were prepared. The solidification microstructure and quantitative information of the GW63K alloys were characterized by using X-ray tomography technique and SEM. The effects of cooling rate on the microstructure and quantitative information were discussed. Besides, the quantitative relationships between cooling rate and volume fractions of the eutectics and secondary phase were proposed, respectively. The results show that the eutectics of GW63K alloy which distribute at the grain boundaries present network-like morphology, and the secondary phase with irregular morphology distributes in the eutectics. With the increase of cooling rate in the range of 0.13-0.33 ℃/s, the primary phase with six-fold symmetry is refined. The eutectic networks become denser, more homogeneous and continuous. The secondary phase distributed more dispersively, and the average size of secondary phase become lower. In addition, the volume fractions of eutectics and secondary phase reduce with increasing the cooling rate.
Key words: Mg-Gd-Y-Zr; controlled cooling rate; X-ray tomography technique
