Reasons for the enhanced phase stability of Ru-containing nickel-based superalloys
Reasons for the enhanced phase stability of Ru-containing nickel-based superalloys
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DOI：
10.1016/j.actamat.2011.07.002
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发表时间：
2011-10-01
期刊：
影响因子：
9.4
通讯作者：
Singer, R. F.
中科院分区：
文献类型：
--
作者：
Heckl, A.;Neumeier, S.;Singer, R. F.
在镍基高温合金的发展中，Ru的加入对相稳定性的改善是众所周知的。然而，这种益处的关键机制尚不清楚。采用逐步增加Ru添加量的新合金系列，系统地研究了Ru对TCP相抑制的影响。此外，还对一种鲜为人知的TCP地层进行了调查，即所谓的不连续降水。与通常研究的枝晶区域的TCP板相比，这种类型的TCP相形成具有两个主要优点。首先，它的微观结构比精细的TCP板要粗糙得多，因此可以进行可靠且耗时更少的调查。其次，不连续析出将过饱和和不稳定的伽玛/伽玛微观结构转变为接近平衡的状态，从而可以有意义地了解稳定的合金成分。对合金相稳定性依赖于Ru的实验结果进行了评价，考虑了Ru对TCP相抑制的所有可能影响。此外，实验证据表明，钌的加入增加了Re在伽马矩阵中的溶解度，这在相应的热钙计算中没有看到。这一发现可能是导致含钌合金TCP相性能提高的主要原因。建立了一个三元相图模型来描述这种新方法。(C) 2011材料学报Elsevier Ltd.出版。版权所有。
Improvements in phase stability on the addition of Ru are well known in the field of nickel-based superalloy development. However, the key mechanism of this benefit remains unclear. A new alloy series with stepwise increased additions of Ru was used to systematically investigate the impact of Ru on yopologically close-packed (TCP) phase inhibition. In addition, the investigation was carried out on a less known type of TCP formation, the so-called discontinuous precipitation. This type of TCP phase formation offers two major advantages compared with commonly investigated TCP plates in dendritic regions. First, the microstructure is much coarser than fine TCP plates, allowing reliable and less time consuming investigations. Second, discontinuous precipitation transforms the supersaturated and unstable gamma/gamma' microstructure in a condition close to equilibrium, permitting a meaningful insight into the stable alloy constitution. The experimental results for alloy phase stability dependence on Ru are evaluated with respect to all possible effects of TCP phase inhibition by Ru. Furthermore, experimental evidence for increased Re solubility in the gamma matrix was found on addition of Ru, which is not seen in corresponding ThermoCalc calculations. This finding is probably the dominant reason for the increased TCP phase capability of Ru-containing alloys. A ternary phase diagram model has been developed to describe the new approach. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.