Abstract The effect of Tungsten (W) on the precipitate evolution and mechanical properties of the alumina-forming austenitic stainless steels (AFAs) Fe-15Cr-25Ni-3Al-NbWCu during aging at 700 °C was systematically investigated. After aging at 700 °C, microstructural characterization revealed that both of the secondary NbC and L12-ordered Ni-Cu-Al phases were precipitated in the matrix of the two steels for strengthening alloys, but W-added AFA (AFA-W) steel exhibited a smaller average size of Ni-Cu-Al phase than AFA steel. In addition, most of the precipitates in AFA steels were δ-ferrite phase with prolonging the aging time, and few Fe2Nb-type Laves phases were observed in the 1000 h-aged AFA samples. However, the addition of W promoted the precipitation of Fe2W-type Laves phases and increased its volume fraction during the aging period. The continuity of δ-ferrite at the grain boundary of AFA-W steels was also interrupted by the co-precipitated Fe2W Laves phase and B2-NiAl phase, avoiding the formation of detrimental δ-ferrite network. Compared to AFA steels, AFA-W steels exhibited higher room temperature tensile properties at the same aging time, which may be caused by the strengthening effect of more dispersed Fe2W phases and smaller sizes of Ni-Al-Cu phases in the grain interiors. Meanwhile, the stress concentration on the triple junctions caused by δ-ferrite was decreased by Fe2W precipitates; thus, further resulting in an increased ductility compared to the AFA steels without W addition.

中文翻译：

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W添加对时效氧化铝形成奥氏体不锈钢Fe-15Cr-25Ni-3Al-NbWCu的析出控制及其对力学性能的影响

摘要 系统地研究了钨 (W) 对形成氧化铝的奥氏体不锈钢 (AFA) Fe-15Cr-25Ni-3Al-NbWCu 在 700 °C 时效过程中析出物演化和力学性能的影响。在 700 °C 时效后，显微组织表征表明，两种钢的基体中均析出二次 NbC 和 L12 有序的 Ni-Cu-Al 相用于强化合金，但添加 W 的 AFA (AFA-W) 钢与 AFA 钢相比，Ni-Cu-Al 相的平均尺寸更小。此外，随着时效时间的延长，AFA钢中大部分析出物为δ-铁素体相，在1000 h时效AFA样品中观察到很少的Fe2Nb型Laves相。然而，W 的加入促进了 Fe2W 型 Laves 相的析出，并在时效期间增加了其体积分数。AFA-W 钢晶界处 δ-铁素体的连续性也被共沉淀的 Fe2W Laves 相和 B2-NiAl 相中断，避免了有害 δ-铁素体网络的形成。与 AFA 钢相比，AFA-W 钢在相同的时效时间内表现出更高的室温拉伸性能，这可能是由于晶粒内部更分散的 Fe2W 相和更小尺寸的 Ni-Al-Cu 相的强化作用所致。同时，Fe2W析出物降低了δ-铁素体引起的三重结应力集中；因此，与没有添加 W 的 AFA 钢相比，进一步提高了延展性。避免形成有害的δ-铁氧体网络。与 AFA 钢相比，AFA-W 钢在相同的时效时间内表现出更高的室温拉伸性能，这可能是由于晶粒内部更分散的 Fe2W 相和更小尺寸的 Ni-Al-Cu 相的强化作用所致。同时，Fe2W析出物降低了δ-铁素体引起的三重结应力集中；因此，与没有添加 W 的 AFA 钢相比，进一步提高了延展性。避免形成有害的δ-铁氧体网络。与 AFA 钢相比，AFA-W 钢在相同的时效时间内表现出更高的室温拉伸性能，这可能是由于晶粒内部更分散的 Fe2W 相和更小尺寸的 Ni-Al-Cu 相的强化作用所致。同时，Fe2W析出物降低了δ-铁素体引起的三重结应力集中；因此，与没有添加 W 的 AFA 钢相比，进一步提高了延展性。Fe2W析出物降低了δ-铁氧体引起的三重结应力集中；因此，与没有添加 W 的 AFA 钢相比，进一步提高了延展性。Fe2W析出物降低了δ-铁氧体引起的三重结应力集中；因此，与没有添加 W 的 AFA 钢相比，进一步提高了延展性。