期刊
ACTA MATERIALIA
卷 194, 期 -, 页码 577-586出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2020.05.043
关键词
Aluminum alloy; Precipitate stability; Microalloying; Atom probe tomography; Density functional theory
资金
- DOE Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office, Propulsion Materials Program
- DOE Basic Energy Sciences, Materials Sciences and Engineering Division
- Oak Ridge Leadership Computing Facility at the ORNL
- Department of Energy, Laboratory Directed Research and Development program at Oak Ridge National Laboratory
Microstructural stability is a critical factor to consider when designing new alloys for high-temperature applications. An Al-Cu alloy with Mn and Zr additions has recently been developed to withstand extended exposures of up to 350 degrees C. The addition of Mn in combination with Zr and their segregation to precipitate interfaces play a significant role in stabilizing the metastable theta' precipitates responsible for the alloy's hardness; however, adding Zr and Mn separately only improves the stability to 200 degrees C and 300 degrees C, respectively. To this end, the effect of the synergistic additions on interfacial structure and chemistry was studied in detail using atom probe tomography (APT) and scanning transmission electron microscopy (STEM) for Al-Cu-Mn-Zr/Ti-containing alloys subjected to long-term annealing (up to 2,100 h) in the critical temperature range, 300 degrees C and 350 degrees C, to investigate the role of Zr/Ti in increasing the theta'-precipitate stability. The APT and STEM results reveal that Mn additions stabilize theta' long enough for the slower diffusing Zr atoms to segregate to coherent theta' interfaces that eventually create a theta'/L1(2)-Al-3 (Zr-x,Ti1-x) co-precipitate structure. The co-precipitate is highly stable, as shown by density functional theory calculations, and is a key factor that governs microstructural stability beyond 300 degrees C. This study reveals how solute additions with different stabilization mechanisms can work in concert to stabilize a desired microstructure, and the results provide insights that can be applied to other high-temperature alloy systems. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd.
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