富稀土晶界相对三种热变形钕铁硼合金矫顽力的影响

Effects of Rich-Rare-Earth Grain-Boundary Phase on Coercive Force of Three Kinds of Die-Upset Neodymium-Iron-Boron Alloys

为分析影响热变形钕铁硼磁体矫顽力的因素,制备了3种不含Dy,Ga热变形磁体,磁体成分分别为Nd10.5Pr2.5Fe80Nb1B6,Nd11.5Fe81.8B6.0Nb0.7+6%Nd67Cu33及Nd10.5Pr2.5Fe80Nb1B6+6%Nd67Cu33,由Nd-Fe-B三元相图计算了富稀土晶界相体积分数v,实验结果表明:v对富稀土钕铁硼热变形磁体矫顽力的贡献为98.10 k A·m-1·%-1,比v对贫稀土钕铁硼混粉热变形磁体矫顽力的贡献低36%~44%;由v=1-a3/[(a+h)2(a+3h)]计算了富稀土晶界相厚度h,发现在v相同条件下热变形钕铁硼磁体晶界相厚度h随主相片状晶等效平均晶粒尺寸a的减小虽然减薄,但a占主导作用导致磁体的矫顽力仍然提高;在片状晶等效平均晶粒尺寸a相近的条件下,热变形钕铁硼磁体晶界相厚度随晶界相体积分数v的增加而变厚,主相片状晶的磁绝缘效果提高导致热变形磁体的矫顽力上升。

To analyze factors affecting the coercive force of die-upset Nd-Fe-B magnets, three alloys free of both Dy and Ga were first hot-pressed and then hot-deformed, such as Nd10.5Pr2.5Fe80Nb1B6,Nd11.5Fe81.8B6.0Nb0.7＋6% Nd67Cu33 and Nd10.5Pr2.5Fe80Nb1B6 ＋6% Nd67Cu33. The volume percentage V and the thickness h of the rich-rare-earth grain-boundary phase were calculated respectively according to the Nd-Fe-B phase diagram and the formula V = 1 -α^3/[（α＋h）^2（α＋3h）]. The coercive forces of the die-upset magnets with the rich-RE Nd-Fe-B particles mixed with Nd67Cu33 ones, are improved 98.10 kA·m^-1·%^-1, by the grain-boundary phase. The value is 36%- 44% lower than those of the magnets with the lean-RE Nd-Fe-B particles mixed with Nd-Cu. Although the thick- ness is reduced the same as the equivalent average grain size a of the matrix phase, under the condition of the same volume fraction V, the coercive forces of the die-upset magnets are increased for the major role of the grain size. If the grain sizes are similar, and the grain-boundary phase is thickened as its volume fraction is increased, and the coercive forces are improved for its bigger magnetic insulation of the matrix-phase grains.