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Interfacial Segregation in Al-Cu-Mg Alloys

Published online by Cambridge University Press:  02 July 2020

R.G. Ford ,
R.W. Carpenter ,
M.J. Kim  and
K. Sieradzki
R.G. Ford
Affiliation:
Science and Engineering of Materials Program and Center for Solid State Science, Arizona State University, Tempe, AZ85287-1704
R.W. Carpenter
Affiliation:
Science and Engineering of Materials Program and Center for Solid State Science, Arizona State University, Tempe, AZ85287-1704
M.J. Kim
Affiliation:
Science and Engineering of Materials Program and Center for Solid State Science, Arizona State University, Tempe, AZ85287-1704
K. Sieradzki
Affiliation:
Science and Engineering of Materials Program and Center for Solid State Science, Arizona State University, Tempe, AZ85287-1704
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Extract

The corrosion behavior of Al-Cu-Mg alloys, specifically 2024 alloy (nominally, in weight %, 4.4 Cu, 1.5 Mg, 0.6 Mn), is thought to depend on heterogeneous Cu and Mg distribution through the existence of segregation-dependent local electrochemical cells at the corrosion interface. Few nanospectroscopy measurements of segregation have been made for this or similar alloys. These alloys are precipitation hardenable. The primary precipitating phases are S and the well known Θ(CuAl2) and their metastable intermediates. TEM analysis of aged alloys in this subgroup showed that the orthorhombic S phase (a=4.0Å, b=9.25Å, c=7.15Å) occurred as a thin plate type variant, called S´, within matrix grains and as larger monolithic particles on grain boundaries. Intragranular pricipitate particle densities were heterogeneous particularly near grain boundaries, indicating that strong segregation was present that would result in local electrochemical cells where grain boundaries and large precipitates intersected the alloy surface.

HRTEM and nanospectroscopy are used to analyze the structure and chemistry of heterophase interfaces and grain boundaries.

Type
Segregation and Diffusion Analysis in Materials
Information
Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 547 - 548
Copyright
Copyright © Microscopy Society of America 1997

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References

1.Nutt, S.R. and Carpenter, R.W., Mater. Sci. and Engr. 75 (1985) 169–177.10.1016/0025-5416(85)90187-9CrossRefGoogle Scholar
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3. Special alloy courtesy of Dr.Buchheit, R., Sandia Laboratories, Albuquerque.Google Scholar
4. This research is supported by the U.S. Air Force Office of Scientific Research, under contract F49620-96-1-0475Google Scholar