不同方法制备Fe-Si合金的高温氧化行为

Oxidation Behavior of Fe-Si Alloys Prepared by Different Techniques

采用电弧熔炼(CA)和机械合金化(MA)技术制备了晶粒尺寸差别较大的二元单相Fe-Si合金,并研究了其在900～1000℃纯O_2中的高温氧化行为。结果表明:2种方法制备的Fe-1Si和Fe-3Si合金氧化后均形成了Fe_2O_3→Fe_3O_4+FeO→FeO→FeO+SiO_2结构的氧化膜,均未形成连续的SiO_2保护膜。机械合金化Fe-Si合金的氧化速度均大于相同温度下同成分的熔炼Fe-Si合金,这是因为细晶材料及其氧化生成的氧化膜中包含了更多的晶界,为合金各元素及氧提供了更多的短路扩散通道,使它们的扩散速度均有明显提高,SiO_2富集区(FeO+SiO_2)的快速形成对Fe的进一步向外扩散起到了一定的阻挡作用,但这对提高合金抗高温氧化性能所起的正影响不及Fe的快速扩散对其造成的负影响。

The oxidation behaviour of Fe-Si alloys prepared by casting and mechanical alloying respectively was studied at 900-1000℃ in pure O2. All the alloys formed similar complex scales like Fe2O3→Fe3O4＋FeO→FeO→FeO＋SiO2, but did not form continuous layers of SiO2. The oxidation rates for the mechanically alloyed alloys were higher than those of the corresponding casting alloys. The differences in oxidation rates are attributed to that the grain-size reduction may enhance the diffusivity of oxygen and each element of the alloys. The formation rates of zones rich in SiO2 may be enhanced, but it can not effectively restrain the quick formation of iron oxides.