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Elevated temperature microstructural stability in cast AlCuMnZr alloys through solute segregation

Journal Article · · Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing
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  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Nemak, S.A., Garcia, NL (Mexico)
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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.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1558572
Alternate ID(s):
OSTI ID: 1564500
OSTI ID: 1689895
Journal Information:
Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing, Journal Name: Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing Vol. 765; ISSN 0921-5093
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
Density functional theory (DFT)
Mechanical properties
Microstructural stability
Solute segregation
cast aluminum alloys