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Improvement of room and high temperature tensile properties of NiAl-strengthened ferritic heat-resistant steels through Mo addition
Materials Science and Engineering: A ( IF 6.1 ) Pub Date : 2018-05-12 , DOI: 10.1016/j.msea.2018.05.034
Ken Cho , Kenshi Ikeda , Hiroyuki Y. Yasuda

In order to improve the room and high temperature strength–ductility balance of ferritic Fe-Al-Ni based alloys strengthened by the B2-type NiAl precipitates, Fe-Al-Ni-Cr-Mo alloys was developed. The microstructures and tensile properties of the alloys were examined focusing on Mo content. We found that the 2 at% or 4 at% Mo addition is effective in the improvement of the elongation of the Fe-Al-Ni based alloys at room temperature (RT) while maintaining high strength, which reflects the suppression of intergranular fracture by the strengthening of the bcc matrix by Mo addition. We also found that the RT tensile properties and deformation behavior of the alloys depend strongly on the volume fraction and the size of the NiAl precipitates. For instance, the yield stress decreases by the change in the primary slip direction from <111> to <001> and the formation of the Orowan loops with increasing the volume fraction and the mean diameter of the NiAl precipitates. In addition, the alloy with the appropriate Mo content exhibits a high yield stress above 660 MPa up to 923 K, owing to the solid-solution hardening by Mo addition and the low growth rate of the NiAl precipitates even at high temperatures. These findings indicate that the alloys have a great potential for steam turbines of advanced ultra‐supercritical thermal power plants.



中文翻译:

通过添加钼改善NiAl增强铁素体耐热钢的室温和高温拉伸性能

为了改善由B2型NiAl析出物增强的铁素体Fe-Al-Ni基合金的室温和高温强度-延展性的平衡,开发了Fe-Al-Ni-Cr-Mo合金。以Mo含量为重点对合金的微观结构和拉伸性能进行了研究。我们发现,添加2 at%或4 at%的Mo可以有效地改善室温下(RT)的Fe-Al-Ni基合金的伸长率,同时保持高强度,这反映了通过添加铁可以抑制晶界断裂。通过添加钼来增强密件抄送矩阵。我们还发现,合金的RT拉伸性能和变形行为在很大程度上取决于NiAl析出物的体积分数和大小。例如,屈服应力会随着主滑移方向从<111>变为<< 001>,随着AlAl沉淀物的体积分数和平均直径的增加,形成了Orowan环。另外,具有适当Mo含量的合金由于通过添加Mo而固溶硬化并且即使在高温下NiAl析出物的生长速度也较低,因此在660MPa以上至923K以上时,显示出较高的屈服应力。这些发现表明,该合金在先进的超超临界热电厂的蒸汽轮机中具有巨大的潜力。由于通过添加Mo进行固溶硬化,并且即使在高温下,NiAl的低生长速率也会析出。这些发现表明,该合金在先进的超超临界热电厂的蒸汽轮机中具有巨大的潜力。由于通过添加Mo进行固溶硬化,并且即使在高温下,NiAl的低生长速率也会析出。这些发现表明,该合金在先进的超超临界热电厂的蒸汽轮机中具有巨大的潜力。

更新日期:2018-05-12
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