(北京工业大学 材料科学与工程学院 教育部新型功能材料重点实验室，北京 100124)
摘 要: 采用放电等离子烧结(SPS)技术制备出致密的纳米晶单相SmCo7合金块体。以此纳米晶合金为初始材料，通过系列退火实验系统研究其晶格参数、物相组成和显微组织随晶粒长大的演变特征。结果表明：纳米晶SmCo7相(1:7H)从室温至600 ℃都能保持很好的相稳定性和热稳定性。通过XRD分析和TEM观察证实，纳米晶SmCo7相的失稳分解和晶粒的突发长大是伴随发生的，即在较高温度(高于600 ℃)条件下纳米化稳定的SmCo7相会分解为Sm2Co17相(2:17R)和SmCo5相(1:5H)，同时晶粒组织会急剧粗化；其中SmCo5相会以圆形析出物的形式均匀分布于晶界处和晶粒内部；随着晶粒的长大，六方结构的纳米晶SmCo7相的晶格参数a和单胞体积均线性减小，而轴比c/a则变化不大。
关键字: SmCo7合金；相稳定性；纳米晶；晶格参数
（College of Materials Science and Engineering, Key Lab of Advanced Functional Materials,
Ministry of Education, Beijing University of Technology, Beijing 100124, China）
Abstract:Using the spark plasma sintering technique, the dense nanocrystalline SmCo7 alloys with single-phase structure were prepared. Starting with the prepared nanocrystalline single-phase SmCo7 alloy and the annealing treatments, the changes of the microstructure, lattice parameters and phase stability of the dopant-free SmCo7 magnetic alloy were investigated. It is discovered that the SmCo7 (1:7H) phase has a good single-phase stability from the room temperature up to 600 ℃. At higher temperature, as a concomitant process with the rapidly coarsened grain structure, the SmCo7 phase decomposes into Sm2Co17 (2:17R) and SmCo5 (1:5H) phases, and the 1:5H phase exists as particulate precipitates distributing uniformly in the matrix. In addition, it is found that both the lattice parameter a and cell volume of 1:7H phase exhibit a linear decreasing relationship versus the annealing temperature in the range of 400−700 ℃, while the c/a value changes a little.
Key words: SmCo7 alloy; phase stability; nanograin; lattice parameters
