Onset of Θ' to Θ Phase Transformation in Al-Cu Alloys

37 Pages Posted: 10 Oct 2019

See all articles by Patrick Shower

Patrick Shower

Government of the United States of America - Materials Science and Technology Division; University of Tennessee, Knoxville - Bredesen Center for Interdisciplinary Research and Graduate Education

James R. Morris

Government of the United States of America - Materials Science and Technology Division; University of Tennessee, Knoxville - Department of Material Science and Engineering

Dongwon Shin

Government of the United States of America - Materials Science and Technology Division

Lawrence F. Allard

Government of the United States of America - Materials Science and Technology Division

Balasubramaniam Radhakrishnan

Government of the United States of America - Computational Sciences and Engineering Division

Amit Shyam

Government of the United States of America - Materials Science and Technology Division; University of Tennessee, Knoxville - Bredesen Center for Interdisciplinary Research and Graduate Education

Abstract

The θʹ to θ phase transformation that occurs during overaging in Al-Cu alloys is detrimental for their mechanical properties. Experiments suggest that the onset of this transformation is dependent on the temperature and duration of thermal exposure, but the microstructural conditions which trigger this transformation are still unclear. In this study, the critical conditions associated with the onset of θʹ to θ phase transformation are predicted using thermodynamic analysis. We compare the predicted microstructural conditions with both new and previously reported microstructural observations, and also test the predictions using phase field modeling. This multi-pronged approach suggests that the tendency of a θʹ particle to transform into the θ phase depends primarily on temperature, particle size, and particle aspect ratio. We define a "critical" aspect ratio below which θʹ to θ phase transformation becomes thermodynamically favored and show how this critical aspect ratio increases with both temperature and particle volume. With this approach, the intimate link between phase stability, morphological stability, and coarsening resistance for θʹ precipitates in Al-Cu alloys is illustrated.

Keywords: Al-Cu alloys, θ´-Al2Cu, Phase field simulation, Phase Transformation

Suggested Citation

Shower, Patrick and Morris, James R. and Shin, Dongwon and Allard, Lawrence F. and Radhakrishnan, Balasubramaniam and Shyam, Amit, Onset of Θ' to Θ Phase Transformation in Al-Cu Alloys. Available at SSRN: https://ssrn.com/abstract=3465849 or http://dx.doi.org/10.2139/ssrn.3465849

Patrick Shower (Contact Author)

Government of the United States of America - Materials Science and Technology Division ( email )

Oak Ridge, TN
United States

University of Tennessee, Knoxville - Bredesen Center for Interdisciplinary Research and Graduate Education ( email )

Knoxville, TN 37996
United States

James R. Morris

Government of the United States of America - Materials Science and Technology Division

Oak Ridge, TN
United States

University of Tennessee, Knoxville - Department of Material Science and Engineering

Knoxville, TN 37996
United States

Dongwon Shin

Government of the United States of America - Materials Science and Technology Division ( email )

Oak Ridge, TN
United States

Lawrence F. Allard

Government of the United States of America - Materials Science and Technology Division

Oak Ridge, TN
United States

Balasubramaniam Radhakrishnan

Government of the United States of America - Computational Sciences and Engineering Division

United States

Amit Shyam

Government of the United States of America - Materials Science and Technology Division

Oak Ridge, TN
United States

University of Tennessee, Knoxville - Bredesen Center for Interdisciplinary Research and Graduate Education

Knoxville, TN 37996
United States

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