Nd-Fe-B powders of different compositions were produced by gas atomization. These powders were annealed between 1000 and 1150 °C for several times to study the microstructural evolution. Differential scanning calorimetry was used to determine the thermal transitions on the as-atomized powders and after slow solidification. The microstructure was studied by high resolution scanning electron microscopy at each stage. Electron back scattering diffraction was used to measure grain size and confirm that gas atomized powders are isotropic. It was observed the formation of necks between the particles, densification, and grain growth due to liquid phase sintering. Grain growth and densification occur in parallel by a dissolution-reprecipitation mechanism. The effect of Nd content and Nb addition on the microstructural changes was analyzed in detail, particularly on grain growth. The degree of sintering increases with Nd content, as this element enhances the formation of the liquid phase. Nb addition leads to the formation of precipitates that delay densification and grain growth at 1000 °C, but promote abnormal grain growth at 1100 °C.

通过气体雾化生产不同组成的Nd-Fe-B粉末。这些粉末在1000至1150°C之间退火数次，以研究组织的演变。差示扫描量热法用于确定雾化粉末以及缓慢固化后的热转变。在每个阶段通过高分辨率扫描电子显微镜研究了微观结构。电子背散射衍射用于测量晶粒尺寸并确认气体雾化粉末是各向同性的。观察到由于液相烧结而在颗粒之间形成颈，致密化和晶粒生长。谷物的生长和致密化通过溶解-再沉淀机制同时发生。详细分析了Nd含量和Nb添加量对显微组织变化的影响，特别是在谷物生长方面。烧结程度随Nd含量的增加而增加，因为该元素会增强液相的形成。Nb的添加导致沉淀物的形成，在1000°C时延缓了致密化和晶粒的生长，但在1100°C时却促进了异常晶粒的生长。