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采用机械合金化的方法制备出Ｍｎ７０Ｂｉ３０纳米晶粉末。通过Ｘ射线衍射和饱和磁化强度的测量，研究了球磨过程中样品的结构和磁性的变化。Ｘ射线衍射的测量结果表明，Ｂｉ在Ｍｎ中的固溶度随球磨时间的增加而增加。球磨８０ｈ后，Ｂｉ的固溶度趋于稳定，此时粉末的晶粒尺寸达到１４ｎｍ。球磨初期，样品的饱和磁化强度（σｓ）随球磨时间的增加而增加。球磨１５ｈ，σｓ从零增加到最大值。之后，σｓ随球磨时间的增加而减小。饱和磁化强度的测量结果表明，反铁磁性的Ｍｎ元素和抗磁性的Ｂｉ元素通过机械合金化产生了铁磁性。
Mn70Bi30 nanocrystalline powders were prepared by mechanical alloying. By X-ray diffraction and saturation magnetization measurement, the change of structure and magnetic properties of the sample during ball milling was studied. The X-ray diffraction measurement results show that the solid solubility of Bi in Mn increases with the milling time. After milling for 80h, the solid solubility of Bi tends to be stable, and the grain size of the powder reaches 14nm. At the beginning of ball milling, the saturation magnetization (σs) of samples increases with the milling time. Ball milling 15h, σs increased from zero to maximum. After that, σs decreases as ball milling time increases. The results of saturation magnetization show that the antiferromagnetic Mn element and the diamagnetic Bi element are ferromagnetic by mechanical alloying.