Fe-Al-Cr合金的晶粒控制对合金抗高温氧化性的影响

Effect of grain control of Fe-Al-Cr alloy on its resistance to high temperature oxidation

Fe-Al-Cr合金具有良好的高温抗氧化性,有广泛的应用前景,具有晶粒粗大的特点。通过在Fe-Al-Cr合金中添加镍、碳、铜等奥氏体化元素,使合金在冷却过程中生成FeCr相,以阻碍晶粒长大的方式使合金晶粒尺寸可以控制在100μm以内。探讨了Fe-Al-Cr合金氧化物薄膜形成的机制以及晶粒控制对Fe-Al-Cr合金抗高温氧化性的影响。通过金相显微镜观察高温下经不同氧化时间氧化后的Fe-Al-Cr合金,发现Al2O3薄膜优先形成于晶界,晶界数量增多有利于Al2O3的形成和生长。通过扫描电镜观察和能谱分析,发现在Fe-Al-Cr合金中,(Al0.9Cr0.1)2O3和Al2O3组成了多层氧化物。结合第一性原理计算,得出该多层氧化物是由于Cr的扩散而在合金表面形成的,有助于提高Fe-Al-Cr合金的抗高温氧化性。最后,证实晶粒直径较小的Fe-Al-Cr合金具有更好的抗高温氧化性。

Fe-Al-Cr alloy has wide application prospects with its good resistance to high temperature oxidation,but it usually has the problem of coarse grains.In this research,by adding austenitizing elements such as nickel,carbon and copper to the Fe-Al-Cr alloy,the FeCr phase was formed during the cooling process,which hindered grain growth and the grain size could be controlled within 100μm.The formation mechanism of oxide film and the effect of grain control on the high temperature oxidation resistance of Fe-Al-Cr alloy were discussed.The Fe-Al-Cr alloy oxidized for different oxidation time at high temperature was observed by metallography and it was found that the alumina film preferentially formed at the grain boundary,and the increase in the number of grain boundaries was favorable for the formation and growth of Al2O3.Electron microscopy scan and energy spectrum analysis revealed that(Al0.9Cr0.1)2O3and Al2O3formed a multilayer oxide.Combined with the first principle calculation,it is concluded that the multilayer oxide is formed on the surface of the alloy due to the diffusion of Cr,which is helpful to improving the high temperature oxidation resistance of the Fe-Al-Cr alloy.It is confirmed that the Fe-Al-Cr alloy with a smaller grain size has better resistance to high temperature oxidation.