The needle-like precipitations might be found in many metalic systems, e.g. σ or μ phase in nickel-based alloys, iron or silicon-rich phases in aluminum alloys, some carbides or intermetalic compounds in iron-based alloys, etc., and their presence is generally unfavorable. Whether it is possible to predict the morphology of the phase based on lattice mismatch between phase and alloys' matrix? How to explain formation of needle-like precipitations with respect to elastic anisotropy and magnitude of the misfit strain?
Thank you Mr. Faleh for the link. The authors performed interesting experiment and described the solidification behaviour of the aluminum alloy. They found dependence of intermetelic compounds morphology, as well as their chemical compositions, with cooling rate. However they not explain observed phases' morphology with respect to to elastic anisotropy, etc.
Dear Krzysztof,
The needle axis prefer to be along the direction with small misfit.
1) for simple system, it is possible to predict the orientation relationship and the direction of needle axis. such as, Dahmen, U. "Orientation relationships in precipitation systems." Acta Metallurgica 30.1(1981):63-73.
2) for complex system, the distribution of misfit strain at given orientation relationship will guide you to find the needle axis.
Zhang W Z, Weatherly G C. On the crystallography of precipitation ☆[J]. Progress in Materials Science, 2005, 50(2):181-292.
and our software:
Gu, X. F., T. Furuhara, and W. Z. Zhang. "PTCLab : free and open-source software for calculating phase transformation crystallography." Journal of Applied Crystallography 49.3(2016):1099–1106.
Xinfu
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