混合合金法添加Ga对Nd-Dy-Fe-Co-B烧结磁体的磁性和微观结构的影响

EFFECT OF Ga ADDITION ON THE MAGNETIC PROPERTIES AND MICROSTRUCTURE OF Nd-Dy-Fe-Co-B SINTERED MAGNET PREPARED BY BLENDING METHOD

对用混合合金法制备的Ｎｄ７．６９Ｄｙ６．６２Ｆｅ６４．３３Ｃｏ１４．８３Ｂ６．５３／Ｇａ烧结磁体的磁性和微观结构进行了研究。结果表明：添加０．５％（质量分数）的Ｇａ后，磁体的ｉＨｃ由１２３２ｋＡ／ｍ升高到１８１９ｋＡ／ｍ，在２００℃放置０．５ｈ后的磁通不可逆损失由 ３３．３％下降到 ５％以下．当Ｇａ的添加量达到１．０％左右时，Ｇａ的作用达到最大值．微观结构分析表明，不添加Ｇａ磁体的晶粒边界、尤其是晶界角隅处多呈现弯曲和凹凸不平的形状，添加 Ｇａ磁体的晶粒边界则呈现平滑和近似直线的形状．烧结过程中Ｇａ原子置换Ｎｄ２Ｆｅ１４Ｂ相中Ｆｅ原子形成Ｎｄ２Ｆｅ１４－ｘＧａｘＢ相，与此同时，被置换的Ｆｅ原子进入液相与富Ｎｄ相、富Ｂ相反应形成新的 Ｎｄ２Ｆｅ１４Ｂ域 Ｎｄ２Ｆｅ１４－ｘＧａｘＢ）相，这是导致磁体的磁性和微观结构发生变化的主要原因。

The effect of gallium added by blending method on the magnetic properties, thermal stabilities and microstructures of Nd7.69Dy6.62Fe64.33Co14.83B6.53 sintered magnets was investigated. The experimental results show that, by adding 0.5 (mass fraction, %)Ga, the H-i(c) is increased from 1232 to 1819 kA/m and the irreversible loss of open flux after exposed at 200 degreesC for 0.5 h is reduced from above 33% to below 5%. The addition of proper amount Ga can also enhance (BH)(max) because of the formation of newborn Nd2Fe14-xGaxB hard phases. Microstructure analysis indicates that the grain boundaries of Ga-free Nd-Fe-B magnets appear to be uneven. On the other hand, the boundaries of Ga-containing magnets appear preferentially in straight and smooth shape.