The solidification of Al–Pd–Mn studied by high-energy X-ray diffraction from electrostatically levitated samples

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2017-06-29
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Quirinale, Dante
Kreyssig, Andreas
Saunders, Scott
Messina, Daniel
Straszheim, Warren
Canfield, Paul
Kramer, Matthew
Goldman, Alan
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Canfield, Paul
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Ames National LaboratoryPhysics and Astronomy
Abstract

We report on the results of a high-energy x-ray diffraction study of Al–Pd–Mn to investigate the solidification products obtained during free-cooling using an electrostatic levitation furnace. The primary solidification product from the melt is i-Al–Pd–Mn which coexists with a significant remaining liquid component. As the sample cools further, we find that the solidification pathway is consistent with the liquidus projection and pseudo-binary cut through the ternary phase diagram reported previously. At ambient temperature we have identified the major phase to be the ξ′-phase orthorhombic approximant, along with minor phases identified as Al and, most likely, the R-phase orthorhombic approximant. We have also observed a distinct prepeak in the liquid at high temperature, signifying the presence of extended atomic order. Interestingly, this prepeak was not observed in previous neutron diffraction measurements on the Al–Pd–Mn system. No undercooling was observed preceding the solidification of the i-Al–Pd–Mn phase from the melt which may signal the close similarity of the short-range order in the solid and liquid. However, this can not be clearly determined because of the potential for heterogenous nucleation associated with the presence of an Al2O3 impurity at the surface of the sample.

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This article is published as Quirinale, Dante G., Andreas Kreyssig, Scott Saunders, Daniel Messina, Warren E. Straszheim, Paul C. Canfield, Matthew J. Kramer, and Alan I. Goldman. "The solidification of Al–Pd–Mn studied by high-energy X-ray diffraction from electrostatically levitated samples." Zeitschrift für Kristallographie-Crystalline Materials 232, no. 7-9 (2017): 619-627. DOI: 10.1515/zkri-2016-2037. Posted with permission.

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Sun Jan 01 00:00:00 UTC 2017
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