Elevated temperature microstructural stability in cast AlCuMnZr alloys through solute segregation

Journal Article · 11 August 2019 · Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing

DOI: https://doi.org/10.1016/j.msea.2019.138279 · OSTI ID:1558572

Shyam, Amit  ^[1]; Roy, Shibayan ^[1]; Shin, Dongwon  ^[1]; Poplawsky, Jonathan D.  ^[1]; Allard Jr, Lawrence  ^[1]; Yamamoto, Yukinori  ^[1]; Morris, James  ^[1]; Mazumder, Baishakhi ^[1]; Idrobo Tapia, Juan Carlos  ^[1]; Rodriguez, Andres ^[2]; Watkins, Thomas R.  ^[1]; Haynes, James A.  ^[1]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Nemak, S.A., Garcia, NL (Mexico)

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
• 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