Role of Fe in long-range ordered Ni2Cr precipitates in Ni-Cr-Fe model alloys during isothermal aging
Role of Fe in long-range ordered Ni2Cr precipitates in Ni-Cr-Fe model alloys during isothermal aging
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DOI：
10.1016/j.msea.2023.145162
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发表时间：
2023-05
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影响因子：
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通讯作者：
N. Aerne;D. Sprouster;J. Tucker
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文献类型：
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作者：
N. Aerne;D. Sprouster;J. Tucker
在高温下长期使用期间，新相的析出是工程合金热稳定性的一个问题。在Ni-Cr基合金中，例如，合金690，形成长程有序的Ni 2Cr会导致脆化，并可能影响核电厂部件的寿命。在这项工作中，我们量化的形成和演变的Ni 2Cr沉淀在11 Ni-Cr-Fe模型合金与0，5，7，和10重量%的铁含量，与Ni/Cr原子比为1.8，2.0，2.2，2.4。这些合金在330至475 °C的温度下等温时效长达10，000 h。通过基于同步加速器的X射线衍射和维氏硬度测试对合金进行表征，以量化Ni 2Cr沉淀物尺寸，以及沉淀物尺寸对作为Fe含量的函数的机械性能的影响。在475 °C和418 °C下时效10，000 h后，在具有0和5wt% Fe的所有合金中观察到Ni 2Cr的形成。在418 °C下时效10，000小时后，在含有7wt%Fe的Ni/Cr=2.0的样品中也观察到Ni 2Cr沉淀物。在任何时间和温度组合下，在任何10重量% Fe样品中均未观察到明显的Ni 2Cr迹象。我们发现，面心立方矩阵的晶格收缩和维氏硬度与Ni 2Cr的形成。硬度和晶格收缩的最大变化发生在475 °C下具有0重量% Fe的化学计量合金（Ni/Cr=2.0）中。5重量% Fe合金的材料性质的变化率降低，然而变化的幅度与0重量% Fe合金相似。Ni-Cr合金的沉淀硬化模型的基础上，临界分解剪切应力与弱耦合位错的Ni 2Cr沉淀物的尺寸和硬度之间的明确的联系。无论Fe浓度如何，该趋势在具有Ni 2Cr形成的所有合金中保持。这种重要的结构-性能关系可以直接通过理解Ni 2Cr形成如何影响作为Fe含量的函数的机械性能来帮助定义Ni-Cr-Fe基部件的寿命。
The precipitation of new phases during long-term service at elevated temperatures is a concern for the thermal stability of engineering alloys. In Ni-Cr-based alloys,e.g., Alloy 690, the formation of long-range ordered Ni2Cr causes embrittlement and may impact the lifetime of nuclear power plant components. In this work, we quantify the formation and evolution of Ni2Cr precipitation in eleven Ni-Cr-Fe model alloys with 0, 5, 7, and 10 wt % Fe contents, and with Ni/Cr atomic ratios of 1.8, 2.0, 2.2, 2.4. These alloys were isothermally aged up to 10,000 h at temperatures between 330 and 475 °C. The alloys were characterized by synchrotron-based x-ray diffraction and Vickers hardness testing to quantify Ni2Cr precipitate size, and the impact of precipitate size on the mechanical properties as a function of Fe content. After 10,000 h of aging at 475 °C and 418 °C, the formation of Ni2Cr was observed in all alloys with 0 and 5 wt % Fe. After 10,000 h of aging at 418 °C, Ni2Cr precipitates were also observed in the 7 wt % Fe containing Ni/Cr=2.0 sample. No clear evidence of Ni2Cr was observed in any of the 10 wt % Fe samples at any time and temperature combination. We find that the face-centered cubic matrix lattice contraction and Vickers hardness are correlated with the Ni2Cr formation. The greatest change in hardness and lattice contraction occurs in stoichiometric alloys (Ni/Cr=2.0) with 0 wt % Fe at 475 °C. The rate of change in the material properties for the 5 wt % Fe alloys is reduced, however the magnitude of changes is similar to 0 wt % Fe alloys. A precipitation hardening model developed for Ni-Cr alloys based on critical resolved shear stress with weakly coupled dislocations shows a clear link between Ni2Cr precipitate size and hardness. This trend held across all alloys with Ni2Cr formation regardless of Fe concentration. This important structure-property relationship can potentially help define Ni-Cr-Fe-based component lifetimes directly through an understanding of how Ni2Cr formation impacts mechanical properties as a function of Fe content.