On the formation of nano-sized precipitates during cooling of NiAl- strengthened ferritic alloys
On the formation of nano-sized precipitates during cooling of NiAl- strengthened ferritic alloys
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DOI：
10.1016/j.matchar.2020.110722
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发表时间：
2020-10
影响因子：
4.7
通讯作者：
R. Lawitzki;D. Beinke;Di Wang;G. Schmitz
中科院分区：
文献类型：
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作者：
R. Lawitzki;D. Beinke;Di Wang;G. Schmitz
本文对作为高温结构材料的铁素体高温合金中的NiAl型析出相进行了实验研究。本研究的重点是表征的超细析出物，形成在样品冷却过程中的时效处理后，对合金的室温硬度有很大的影响。通过电子显微镜获得沉淀物的尺寸和晶体学信息。采用原子探针层析技术分析了不同相的化学性质。为了识别APT重构中的超精细沉淀，提出了一种改进的最大分离法用于簇选择。而不是一个单独的腐蚀步骤，所提出的方法利用的Delaunay曲面细分，不需要任何用户定义的输入参数，并进一步，给出了一个直接访问的聚类形态。修改后的算法在模拟数据集上进行了测试，然后成功地应用于实验数据集，其中包含半径为1纳米的沉淀物。化学分析的结果表明，在样品冷却过程中沉淀的形成是一个动力学控制的过程，这是由两个不同的机制取决于温度占主导地位。
We present an experimental study on NiAl- type precipitates in ferritic superalloys that aim for application as structural materials at high temperature. The focus of this study is on the characterization of hyperfine precipitates that form during sample cooling after the aging treatment and which have a strong influence on the alloys' room temperature hardness. Size and crystallographic information of the precipitates were obtained by electron microscopy. The chemical nature of different phases was analyzed by atom probe tomography (APT). In order to identify the hyperfine precipitates in APT reconstructions, a modified version of the maximum separation method for cluster selection is proposed. Instead of a separate erosion step, the proposed method makes use of a Delaunay tessellation which does not require any user defined input parameters and further, gives a direct access to the morphology of the clusters. The modified algorithm was tested on simulated datasets and then successfully applied to experimental datasets containing precipitates with radii down to one nanometer. The result of the chemical analysis shows that the formation of precipitates during sample cooling is a kinetically controlled process which is dominated by two different mechanisms in dependence on the temperature.