To know reason for negative effect of Nb addition on oxidation resistance in alumina-forming austenitic stainless steels at high temperature, effects of Nb addition on microstructural evolution and oxidation resistance were investigated in Fe-25Ni-10Cr-4.5Al based steels after oxidation at 1323 K. The results showed that the degraded oxidation resistance due to the Nb addition resulted from suppressed outward diffusion of Al atoms by formation of Fe₂Nb phase. Pre-aging at 1223 K could improve the oxidation resistance of the Nb-containing Fe-25Ni-10Cr-4.5Al steel due to the pre-precipitated B2-NiAl phase.

中文翻译：

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Nb添加对形成氧化铝的奥氏体不锈钢在1323 K抗氧化性产生负面影响的原因

为了解 Nb 添加对氧化铝形成的奥氏体不锈钢高温抗氧化性产生负面影响的原因，研究了 Nb 添加对 Fe-25Ni-10Cr-4.5Al 基钢在 1323 氧化后的显微组织演变和抗氧化性的影响K. 结果表明，由于形成 Fe ₂ Nb 相抑制了 Al 原子的向外扩散，Nb 的添加导致抗氧化性降低。由于预析出B2-NiAl相，1223 K预时效可以提高含Nb Fe-25Ni-10Cr-4.5Al钢的抗氧化性。