采用Ｘ射线衍射，透射电镜等测试手段，对硅脆的临界硅含量前后的铁－碳－硅合金的硅脆机理进行了探讨。结果表明，合金硅脆的临界硅含量同时又是合金无序—有序化的转变点。超过硅脆的临界硅含量的合金，存在长程有序结构，一种是ＤＯ３型的Ｆｅ３Ｓｉ相，另一种是Ｂ２型的ＦｅＳｉ相，退火或高温长期退火均不能减少有序化带来的脆化现象。因此，合金的有序化是导致硅脆的根本原因 The mechanism of silicon embrittlement of iron-carbon-silicon alloy before and after the critical silicon content of silicon embrittlement was investigated by X-ray diffraction and transmission electron microscopy. The results show that the critical silicon content of the alloy is at the same time a disorderly-ordered transition point of the alloy. Exceed the critical silicon content of silicon brittle silicon alloy, there is long-range orderly structure, one is the DO3-type Fe3Si phase and the other is the B2-type FeSi phase, annealed or high temperature long-term annealing can not reduce the ordering of the brittle The phenomenon. Therefore, the ordering of the alloy is the fundamental cause of silicon fragility