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Figure 1
Typical example of trans-scale observation of the solidification microstructure in HEAs [2,3]
Trans-scale observations using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Electron Probe Micro Analyzer (EPMA), Transmission Electron Microscopy (TEM), and Scanning Transmission Electron Microscopy (STEM) [1] is effective to clarify the solidification microstructure of High Entropy Alloys especially for the macro-segregation and micro-segregation. Figure 1 shows the typical example of trans-scale observation of the solidification microstructure in AlCoCrFeNi2.1 eutectic HEAs [2,3].
REFERENCES
[1] T. Nagase, A. Yokoyama and Y. Umakoshi, J. of alloys and compounds, 494, 295-300 (2010)., "Multi-Scale Crystalline Cu Globule Dispersed Fe-Based Metallic Glass Formation by Multi-Step Liquid Phase Separation", http://dx.doi.org/10.1016/j.jallcom.2010.01.015
[2] T. Nagase, M. Takemura, M. Matsumuro, T. Maruyama, Materials Transactions, Sharing publication - JFS and JIM, in press, "Solidification microstructure analysis of AlCoCrFeNi2.1 eutectic high entropy alloy ingots", http://doi.org/10.2320/matertrans.F-M2017851
[3] 永瀬丈嗣, 武村守, 松室光昭, 丸山徹, 鋳造工学, 89, 119-129 (2017)., "AlCoCrFeNi2.1共晶型ハイエントロピー合金鋳造材の凝固組織", http://doi.org/10.11279/jfes.89.119
AlCoCrFeNi2.1 Eutectic HEAs
Figure 1
Typical example of cast process dependence on the solidification microstructure in AlCoCrFeNi2.1 Eutectic HEAs [3-5]
Eutectic High Entropy Alloys (EHEAs) were suggested based on the concept of combining bcc- and fcc-structured HEAs to achieve a balance of strength and ductility by Lu et al. [1,2]. The composite structure could be obtained from the eutectic reaction occurring in the thermal melt during solidification. The fabrication of industrial-scale ingots of AlCoCrFeNi2.1 EHEAs was attempted to research future applications for engineering cast materials. The influence of the cast process on the solidification microstructure in AlCoCrFeNi2.1 EHEAs was investigated [3-5]. The size of the microstructure exhibited a cooling-rate dependence; as the cooling rate increased, the secondary dendrite space arming and lamellar size of the eutectic structure became finer [3,4]. The rapidly solidified melt-spun ribbon shows a fine poly-crystalline structure with fcc matrix phase and crystalline precipitates in the grain boundary, indicating that the solidification structure in the melt-spun ribbon was significantly different from that obtained by conventional casting processes [5].
REFERENCES
[1] Y. Lu, Y. Dong, S. Guo, L. Jiang, H. Kang, T. Wang, B. Wen, Z. Wang, J. Jie, Z. Cao, H. Ruan, T. Li, "A Promising New Class of High-Temperature Alloys: Eutectic High-Entropy Alloys", Sci. Rep., 4 (2014) 06200 1-5., http://doi.org/10.1038/srep06200
[2] Y. Lu, X. Gao, L. Jiang, Z. Chen, T. Wang, J. Jie, H. Kang, Y. Zhang, S. Guo, H. Ruan, Y. Zhao, Z. Cao, T. Li, "Directly cast bulk eutectic and near-eutectic high entropy alloys with balanced strength and ductility in a wide temperature range", Acta Mater., 124 (2017) 143-150., https://doi.org/10.1016/j.actamat.2016.11.016
[3] T. Nagase, M. Takemura, M. Matsumuro, T. Maruyama, Materials Transactions, Sharing publication - JFS and JIM, in press, "Solidification microstructure analysis of AlCoCrFeNi2.1 eutectic high entropy alloy ingots", http://doi.org/10.2320/matertrans.F-M2017851
[4] 永瀬丈嗣, 武村守, 松室光昭, 丸山徹, 鋳造工学, 89, 119-129 (2017)., "AlCoCrFeNi2.1共晶型ハイエントロピー合金鋳造材の凝固組織", http://doi.org/10.11279/jfes.89.119
[5] T. Nagase%%%, M. Takemura, M. Matsumuro, Mater. Sci. Forum, 879 (2017) 1350-1354., "Microstructure of Rapidly Solidified Melt-Spun Ribbon in AlCoCrFeNi2.1 Eutectic High-Entropy Alloys", http://www.ttp.net/978-3-0357-1129-5/23.html
