Effect of composition on the matrix transformation of the Co-Re-Cr-Ta-C alloys
Effect of composition on the matrix transformation of the Co-Re-Cr-Ta-C alloys
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DOI：
10.1007/s12540-016-5697-2
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发表时间：
2016-07-01
影响因子：
3.5
通讯作者：
Rosler, Joachim
中科院分区：
文献类型：
--
作者：
Beran, Premysl;Mukherji, Debashis;Rosler, Joachim
在高温下对添加和不添加 Cr 的 Co-Re-Ta-C 合金进行原位中子衍射测量。这包括含有不同 C 含量且 C/Ta 比率在 0.5 至 1.0 之间变化的合金。实验合金的Co-Re-固溶体基体是多晶型的（就像纯钴一样），并且在加热时从低温六方E > 相转变为高温立方γ相。这种转变是可逆的并且表现出滞后现象。主要合金添加物 Re 可稳定 E > Co 相，并将转变温度提高到 1273 K 以上。加热和冷却过程中转变的开始时间根据合金成分的不同而有所不同。在不添加Cr的合金中，冷却时相变并未完成，高温γ相在室温下以亚稳态部分保留，其量取决于从高温开始的冷却速率。衍射和显微结构结果表明Cr是E>稳定剂（与Re类似），但Ta的作用尚不清楚。 C/Ta比对基体相变没有直接影响。然而，它通过确定基体中可自由获得的 Ta 的量来间接影响。
Neutron diffraction measurement was performed in-situ at high temperatures on Co-Re-Ta-C alloys with and without Cr addition. This included alloys containing different C content with the C/Ta ratio varying between 0.5 and 1.0. The Co-Re-solid solution matrix of the experimental alloys is polymorphic (like in pure cobalt) and transformed from low temperature hexagonal E > phase to high temperature cubic gamma phase on heating. This transformation is reversible and show hysteresis. The main alloying addition, Re, stabilizes the E > Co-phase and increases the transformation temperature to above 1273 K. The onset of the transformation during heating and cooling was found to differ depending on the alloy composition. In alloys without Cr addition the transformation was not completed on cooling and the high temperature gamma phase was partly retained at room temperature in metastable state with the amount depending on the cooling rate from high temperature. The diffraction and microstructural results showed that Cr is E > stabilizer (similar as Re) but the role of Ta is not clear. The C/Ta ratio has no direct effect on the matrix phase transformation. Nevertheless, it influences indirectly by determining the amount of Ta which is freely available in the matrix.