中文摘要：

采用氩气保护气氛高能球磨和真空热压技术制备了致密度大于98％的纳米晶CuCr25合金，并在真空室内进行击穿试验。采用扫描电镜对纳米晶和粗晶CuCr25合金阴极斑点蚀坑形貌进行观察。结果表明：粗晶CuCr25合金真空电弧阴极斑点扩散表现为原地重复燃烧或整体的跳跃式移动，且有选择地分布在Cr相。而纳米晶CuCr25合金由于晶粒细化（〈50nm），为电子发射提供了优越条件，阴极斑点的扩散表现为次级斑点的此起彼伏的准连续移动，击穿相均匀分布在整个阴极表面。

英文摘要：

The nano-crystalline CuCr25 alloys have been prepared and the breakdown experiments have been done in vacuum room. The traces of cathode spots on the surface of coarse-crystalline and nano-crystalline CuCr25 alloys have been observed using a scanningelectron microscope （SEM）. Experimental results show that the spot diffusion of coarse-crystalline CuCr25 cathode local iterative combustion or whole jumping move on the Cr phases with a weak voltage withstanding. But the spot diffusion of nanocrystallization of CuCr25 cathode exhibits quasi-continuous move, as one falls and another rises, due to the superior condition for electron emission, and the breakdown phase distributing on the whole cathode surface.