Dormidontov Andrey G, Kolchugina Natalia B, Dormidontov Nikolay A, Zheleznyi Mark V, Bakulina Anna S, Prokofev Pavel A, Andreenko Aleksandr S, Milov Yury V, Sysoev Nikolay N
LLC "MEM", 123458 Moscow, Russia.
Materials (Basel). 2021 Dec 15;14(24):7762. doi: 10.3390/ma14247762.
Observations of the surface domain structure (Kerr-effect), optical metallography, scanning electron microscopy (SEM-SE), and electron microprobe analysis (EPMA-SEM), measurements of major and minor magnetic hysteretic loops were used to study pseudo-single-crystal samples of (Sm,Zr)(Co,Cu,Fe) alloys subjected to heat treatments to the high-coercivity state, which are used in fabricating sintered permanent magnets. Correlations between the chemical composition, hysteretic properties, structural components, domain structure, and phase state were determined for the concentration ranges that ensure wide variations of 4f-/4d-/3d-element ratio in the studied samples. The phase state formed by collinear and coherent phase components determines the high coercive force and ultimate magnetic hysteresis loops of the pseudo-single crystals. It was found that the 1:5 phase with the hexagonal structure (P6/mmm) is the matrix of the alloys for (Sm,Zr)(Co,Cu,Fe) permanent magnets; the matrix undergoes phase transformations in the course of all heat treatments for the high-coercivity state. The heterogeneity observed with optical magnifications, namely, the observation of main structural components A and B, is due to the alternation, within the common matrix, of regions with modulated quasi-spherical precipitates and regions with hexagonal bipyramids (cellular phase) although, traditionally, many investigators consider the cellular phase as the matrix. It is shown that the relationship of volume fractions of structural components A and B that account for more than 0.9 volume fraction of the total, which is due to the integral chemical composition of the alloys, determines the main hysteretic performances of the samples. The Zr-rich phases, such as 5:19, 2:7, and 6:23, and a structural component with the variable stoichiometry (Sm(Co,Cu,Fe)) that is almost free of Zr and contains up to 33 at% Cu, were found only within structural component A in quantities sufficient for EPMA analysis.
利用对表面畴结构（克尔效应）、光学金相学、扫描电子显微镜（SEM-SE）和电子微探针分析（EPMA-SEM）的观察，以及对主要和次要磁滞回线的测量，研究了经热处理至高矫顽力状态的(Sm,Zr)(Co,Cu,Fe)合金的伪单晶样品，这些样品用于制造烧结永磁体。针对确保所研究样品中4f-/4d-/3d-元素比例有广泛变化的浓度范围，确定了化学成分、磁滞性能、结构组分、畴结构和相态之间的相关性。由共线且相干的相组分形成的相态决定了伪单晶的高矫顽力和最终磁滞回线。发现具有六方结构（P6/mmm）的1:5相是(Sm,Zr)(Co,Cu,Fe)永磁体合金的基体；在所有高矫顽力状态的热处理过程中，该基体都会发生相变。在光学放大倍数下观察到的不均匀性，即观察到主要结构组分A和B，是由于在共同基体内，具有调制准球形析出物的区域和具有六方双锥体（胞状相）的区域交替出现，尽管传统上许多研究者将胞状相视为基体。结果表明，占总体积分数超过0.9的结构组分A和B的体积分数关系，由合金的整体化学成分决定，它决定了样品的主要磁滞性能。仅在结构组分A内发现了富Zr相，如5:19、2:7和6:23，以及一种几乎不含Zr且含高达33 at% Cu的可变化学计量比的结构组分（Sm(Co,Cu,Fe)），其含量足以进行电子微探针分析。
