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Title: Elevated temperature microstructural stability in cast AlCuMnZr alloys through solute segregation

Abstract

Commonly used commercial cast aluminum alloys for the automotive industry are viable for temperatures only up to 250 °C, despite decades of study and development. Affordable cast aluminum alloys with improved high-temperature mechanical properties are needed to enable the next generation of higher efficiency passenger car engines. Metastable θ' (Al2Cu) precipitates contribute to strengthening in Al–Cu alloys, but above 250 °C coarsen and transform, leading to poor mechanical properties. A major challenge has been to inhibit coarsening and transformation by stabilizing the metastable precipitates to higher temperatures. In this work, we report compositions and associated counter-intuitive microstructures that allow cast Al–Cu alloys to retain their strength after lengthy exposures up to 350 °C, ~70% of their absolute melting point. Atomic-scale characterization along with first-principles calculations demonstrate that microalloying with Mn and Zr (while simultaneously limiting Si to < 0.1 wt %) is key to stabilization of high-energy interfaces. Lastly, it is suggested that segregation of Mn and Zr to the θ' precipitate-matrix interfaces provides the mechanism by which the precipitates are stabilized to a higher homologous temperature.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1];  [2]; ORCiD logo [1]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Nemak, S.A., Garcia, NL (Mexico)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
OSTI Identifier:
1558572
Alternate Identifier(s):
OSTI ID: 1564500
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing
Additional Journal Information:
Journal Volume: 765; Journal ID: ISSN 0921-5093
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; cast aluminum alloys; Solute segregation; Microstructural stability; Mechanical properties; Density functional theory (DFT)

Citation Formats

Shyam, Amit, Roy, Shibayan, Shin, Dongwon, Poplawsky, Jonathan D., Allard Jr, Lawrence, Yamamoto, Yukinori, Morris, James, Mazumder, Baishakhi, Idrobo Tapia, Juan Carlos, Rodriguez, Andres, Watkins, Thomas R., and Haynes, James A.. Elevated temperature microstructural stability in cast AlCuMnZr alloys through solute segregation. United States: N. p., 2019. Web. https://doi.org/10.1016/j.msea.2019.138279.
Shyam, Amit, Roy, Shibayan, Shin, Dongwon, Poplawsky, Jonathan D., Allard Jr, Lawrence, Yamamoto, Yukinori, Morris, James, Mazumder, Baishakhi, Idrobo Tapia, Juan Carlos, Rodriguez, Andres, Watkins, Thomas R., & Haynes, James A.. Elevated temperature microstructural stability in cast AlCuMnZr alloys through solute segregation. United States. https://doi.org/10.1016/j.msea.2019.138279
Shyam, Amit, Roy, Shibayan, Shin, Dongwon, Poplawsky, Jonathan D., Allard Jr, Lawrence, Yamamoto, Yukinori, Morris, James, Mazumder, Baishakhi, Idrobo Tapia, Juan Carlos, Rodriguez, Andres, Watkins, Thomas R., and Haynes, James A.. Mon . "Elevated temperature microstructural stability in cast AlCuMnZr alloys through solute segregation". United States. https://doi.org/10.1016/j.msea.2019.138279. https://www.osti.gov/servlets/purl/1558572.
@article{osti_1558572,
title = {Elevated temperature microstructural stability in cast AlCuMnZr alloys through solute segregation},
author = {Shyam, Amit and Roy, Shibayan and Shin, Dongwon and Poplawsky, Jonathan D. and Allard Jr, Lawrence and Yamamoto, Yukinori and Morris, James and Mazumder, Baishakhi and Idrobo Tapia, Juan Carlos and Rodriguez, Andres and Watkins, Thomas R. and Haynes, James A.},
abstractNote = {Commonly used commercial cast aluminum alloys for the automotive industry are viable for temperatures only up to 250 °C, despite decades of study and development. Affordable cast aluminum alloys with improved high-temperature mechanical properties are needed to enable the next generation of higher efficiency passenger car engines. Metastable θ' (Al2Cu) precipitates contribute to strengthening in Al–Cu alloys, but above 250 °C coarsen and transform, leading to poor mechanical properties. A major challenge has been to inhibit coarsening and transformation by stabilizing the metastable precipitates to higher temperatures. In this work, we report compositions and associated counter-intuitive microstructures that allow cast Al–Cu alloys to retain their strength after lengthy exposures up to 350 °C, ~70% of their absolute melting point. Atomic-scale characterization along with first-principles calculations demonstrate that microalloying with Mn and Zr (while simultaneously limiting Si to < 0.1 wt %) is key to stabilization of high-energy interfaces. Lastly, it is suggested that segregation of Mn and Zr to the θ' precipitate-matrix interfaces provides the mechanism by which the precipitates are stabilized to a higher homologous temperature.},
doi = {10.1016/j.msea.2019.138279},
journal = {Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing},
number = ,
volume = 765,
place = {United States},
year = {2019},
month = {8}
}

Journal Article:

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Cited by: 13 works
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Figures / Tables:

Table 1 Table 1: Summary of chemistry (in weight %) of cast aluminum alloys and upper temperature limit for stable mechanical properties. Alloy names of the two alloys whose tensile properties are reported in Figure 1 are underlined. Note that the precipitates in the Al5CuMg alloy (*) go through multiple phase transformationsmore » (GPI to θ′′ to θ′ and then to θ).« less

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