Nanolayered diffusion couple method reconsidering on the binary phase diagram: the miscibility gap
2Department of Solid State Physics, University of Debrecen, Hungary
Mysteries in binary phase diagram are still in existence, e.g., the case in Cu-Ni which is mutual miscible system, the question addressed that “Indirect experimental evidence indicates the presence of a miscibility gap in the fcc phase at a temperature somewhere between 450 and 923 K.” [1].
Recently, author’s group suggests new miscibility gap on Cupper-Nickel system by means of Secondary Neutral Mass Spectroscopy (SNMS) with nanolayered diffusion couple method [2].
Typical metallurgy, miscibility curve (hereafter “binodal line”) is calculated from spinodal line which is experimentally obtained from the annealing of supersaturated alloys, or estimated from thermodynamic parameter. This is an indirect way to determine the binodal line because composition of alloying comes from inside of miscibility gap to just or around at spinodal line.
Conversely, our method is direct determination of binonal line whose composition of alloying comes from outside of miscibility gap to just or around at binodal line. This should be sophisticated way to determine the miscibility gap.
Also we have several problem, slower diffusion, bimetallic strip strain effect[3], chemical/coherent miscibility gap[4], size effect[5], how to differentiate, is it really equilibrium? etc.
In my presentation, we will make further discussion for justification of our procedure and phase diagram with several examples.
[1] Franke, P., & Neuschütz, D. (2005). Binary systems. Part 3: Binary Systems from Cs-K to Mg-Zr. Landolt Börnstein.
[2] Iguchi, Yusuke, et al. arXiv preprint arXiv:1611.07068 (2016).
[3] Tanaka, Keisuke, et al. Journal of the Society of Materials Science, Japan 53(7) (2004) 728.
[4] Jantzen, C. M. F., & Herman, H. (1978). Phase Diagrams: Materials Science and Technology.
[5] Burch, D, and Bazant, M. Z. Nano letters 9(11) (2009) 3795.
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