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Title: Composition and automated crystal orientation mapping of rapid solidification products in hypoeutectic Al-4 at.%Cu alloys

Abstract

Rapid solidification can produce metastable phases and unusual microstructure modifications in multi-component alloys during additive manufacturing or laser beam welding. Composition and phase mapping by transmission electron microscopy have been used in this paper to characterize the morphologically distinct zones developing in hypoeutectic Al-4 at.% Cu alloy after pulsed laser melting for different crystal growth rate regimes. Deviations of the compositions of the alloy phases from equilibrium predictions and unique orientation relationships between the solidification transformation products have been determined. Specifically, for the columnar growth zone at solidification rates of 0.8 m s - 1 < v < v a = 1.8 m s - 1 , two distinct orientation relationships were established between the concomitantly forming non-equilibrium phases, supersaturated α-Al solid solution and the discontinuously distributed α-Al 2Cu-based θ'-phase, which can be described as {110} θ {001} α, [001] θ [110] α and {001} θ {001} α, [100] θ [100] α. These orientation relationships permit formation of coherent interphase interfaces with low interfacial free energy. Finally, this endows a kinetic advantage to the thermodynamically less stable θ'-Al 2Cu phase relative to the more stable equilibrium θ-Al 2Cu phase during formation of the morphologically modified eutectic of the columnar growth zone grains, since repeated nucleation is required to establish the discontinuous distribution of θ'-Al 2Cu phase.

Authors:
ORCiD logo [1];  [2];  [3];  [4];  [4];  [2]
  1. Univ. of Pittsburgh, PA (United States). Dept. of Mechanical Engineering and Materials Science; Swiss Federal Laboratories for Materials Science and Technology (Empa), Dübendorf (Switzerland)
  2. Univ. of Pittsburgh, PA (United States). Dept. of Mechanical Engineering and Materials Science
  3. Univ. of Pittsburgh, PA (United States). Dept. of Mechanical Engineering and Materials Science; FEI Co., Hillsboro, OR (United States)
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Materials Sciences Division
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Pittsburgh, PA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
OSTI Identifier:
1438655
Alternate Identifier(s):
OSTI ID: 1496396
Report Number(s):
LLNL-JRNL-735845
Journal ID: ISSN 1359-6454
Grant/Contract Number:  
AC52-07NA27344; DMR 1105757; DMR 1607922; FWP SCW0974
Resource Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 145; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; rapid solidification; TEM; PED; ACOM; interface velocity; absolute stability

Citation Formats

Zweiacker, K. W., Liu, Can, Gordillo, M. A., McKeown, J. T., Campbell, G. H., and Wiezorek, J. M. K. Composition and automated crystal orientation mapping of rapid solidification products in hypoeutectic Al-4 at.%Cu alloys. United States: N. p., 2017. Web. doi:10.1016/j.actamat.2017.11.040.
Zweiacker, K. W., Liu, Can, Gordillo, M. A., McKeown, J. T., Campbell, G. H., & Wiezorek, J. M. K. Composition and automated crystal orientation mapping of rapid solidification products in hypoeutectic Al-4 at.%Cu alloys. United States. doi:10.1016/j.actamat.2017.11.040.
Zweiacker, K. W., Liu, Can, Gordillo, M. A., McKeown, J. T., Campbell, G. H., and Wiezorek, J. M. K. Tue . "Composition and automated crystal orientation mapping of rapid solidification products in hypoeutectic Al-4 at.%Cu alloys". United States. doi:10.1016/j.actamat.2017.11.040. https://www.osti.gov/servlets/purl/1438655.
@article{osti_1438655,
title = {Composition and automated crystal orientation mapping of rapid solidification products in hypoeutectic Al-4 at.%Cu alloys},
author = {Zweiacker, K. W. and Liu, Can and Gordillo, M. A. and McKeown, J. T. and Campbell, G. H. and Wiezorek, J. M. K.},
abstractNote = {Rapid solidification can produce metastable phases and unusual microstructure modifications in multi-component alloys during additive manufacturing or laser beam welding. Composition and phase mapping by transmission electron microscopy have been used in this paper to characterize the morphologically distinct zones developing in hypoeutectic Al-4 at.% Cu alloy after pulsed laser melting for different crystal growth rate regimes. Deviations of the compositions of the alloy phases from equilibrium predictions and unique orientation relationships between the solidification transformation products have been determined. Specifically, for the columnar growth zone at solidification rates of 0.8 ms-1 < v <va=1.8 ms-1, two distinct orientation relationships were established between the concomitantly forming non-equilibrium phases, supersaturated α-Al solid solution and the discontinuously distributed α-Al2Cu-based θ'-phase, which can be described as {110}θ ∥ {001}α, [001]θ ∥ [110]α and {001}θ ∥ {001}α, [100]θ ∥ [100]α. These orientation relationships permit formation of coherent interphase interfaces with low interfacial free energy. Finally, this endows a kinetic advantage to the thermodynamically less stable θ'-Al2Cu phase relative to the more stable equilibrium θ-Al2Cu phase during formation of the morphologically modified eutectic of the columnar growth zone grains, since repeated nucleation is required to establish the discontinuous distribution of θ'-Al2Cu phase.},
doi = {10.1016/j.actamat.2017.11.040},
journal = {Acta Materialia},
number = ,
volume = 145,
place = {United States},
year = {2017},
month = {12}
}

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