材料期刊网

利用真空热天平、扫描电镜和X-射线衍射仪研究了Fe-15Cr和Fe-15Cr-0.3 Ce合金在1000和1100℃的氧化行为。结果表明,在Fe-15Cr合金表面,Cr_2O_3膜形成后不久便广泛变形、频繁开裂,使富铁氧化物瘤子不断产生。与此相应,氧化动力学曲线反复发生曲折,对抛物线产生正偏离。铈使Cr_2O_3膜变形,开裂和形成瘤子的倾向减小,产生较光滑的动力学曲线,较小的氧化速率。 进一步的研究发现,铈促进Cr_2O_3膜的晶粒成为柱状晶,抑制在膜表面形成新氧化物,并绽膜中(1010)、(104)、(116)等晶面具有较强的择优取向。由此推断出铈具有阻止膜中铬离子扩散、减小膜的生长应力等作用。认为这是铈减轻膜发生变形和开裂的倾向,减小氧化速率的原因。

The oxidation behaviour of Fe-15 Cr and Fe-15Cr-0.3Ce alloys at 1000℃ and 1100℃ has been investigated by means of vacuum-thermo-microbalance, scanning electromicroscope and X-ray diffractometer.Experimental results show that Fe-rich oxide nodules are formed rapidly on the surface of Fe-15Cr alloy owing to deformation and breakdown of Cr_2O_3 film on this alloy. A positive deviation of oxidation kinetics from parabolic law occurs as a result of repeated breaks of weight-gain curves. If the alloy contains Ce, the deformation of the Cr_2O_3 film and the formation of Fe-rich oxide nodules are inhibited, and thus more smooth weight-gain curves and smaller oxidation rates are obtained.lt is found that Ce promotes growth of columnar crystal grains and enhances preferred orientation of the crystal grains in the Cr_2O_3 film. These facts suggest that diffusion of Cr ions in the film and lateral growth of the film can be affected by Ce ions.It might be thought that the above mentioned findings are associated with the decrease of growth stress and deformation of the Cr_2O_3 film.