本文研究了Sm(Co, Cu, Fe, Mn)_(7.8)永磁体铸造结晶组织及Cu偏析对矫顽力的影响。结果表明,不同冷却速度的铸造合金锭具有不同的结晶组织。在等轴晶组织中,晶内贫Cu,晶界上富集游离Cu,保存有一些Sm_2Co_(17-x)T_x六方结构高温相,造成矫顽力下降;而在细的柱状晶组织中,无严重的成分偏析。经烧结和固溶处理后的磁体,为位错胞状显微组织,胞壁间弥散着脱溶Cu和富Cu的SmCo_(5-x)T_x相,它们在反磁化过程中,可能对畴壁起着钉扎作用,因而具有高矫顽力。
Effects of the as-cast crystaline structure and segregation in Cu on the coercivity of Sm(Co, Cu, Fe, Mn)_(7.8) permanent magnets have been investigated. Experimental results showed that the crystalline structure of the ingot is different with different cooling rates. In the equi-axed grain structure, the inner of the grain is deficient in Cu; free Cu concentrates on the grain boundaries, where an amount of high temperature phase of hexagonal structure of Sm_2Co_(17-x)T_x is preserved, resulting in a decrease in the coercivity. In the fine-columnar grain structure, no serious segregation in composition has been observed. Magnets after sintering and solution treatment exhibit the cellular microstructure; precipitated Cu and SmCo_(5-x)T_x phase rich in Cu disperse on the cell-wall. They probably play, in the course of magnetization reversal, the role of pinning the domain wall, hence, giving high coercivity.
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