(北京工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院 教育部新型功能材料重點實驗室，北京 100124)
摘 要: 采用放電等離子燒結(jié)(SPS)技術(shù)制備出致密的納米晶單相SmCo7合金塊體。以此納米晶合金為初始材料，通過系列退火實驗系統(tǒng)研究其晶格參數(shù)、物相組成和顯微組織隨晶粒長大的演變特征。結(jié)果表明：納米晶SmCo7相(1:7H)從室溫至600 ℃都能保持很好的相穩(wěn)定性和熱穩(wěn)定性。通過XRD分析和TEM觀察證實，納米晶SmCo7相的失穩(wěn)分解和晶粒的突發(fā)長大是伴隨發(fā)生的，即在較高溫度(高于600 ℃)條件下納米化穩(wěn)定的SmCo7相會分解為Sm2Co17相(2:17R)和SmCo5相(1:5H)，同時晶粒組織會急劇粗化；其中SmCo5相會以圓形析出物的形式均勻分布于晶界處和晶粒內(nèi)部；隨著晶粒的長大，六方結(jié)構(gòu)的納米晶SmCo7相的晶格參數(shù)a和單胞體積均線性減小，而軸比c/a則變化不大。
關(guān)鍵字: SmCo7合金；相穩(wěn)定性；納米晶；晶格參數(shù)
（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
