The synergistic role of Mn and Zr/Ti in producing θ'/L12 co-precipitates in Al-Cu alloys

Poplawsky, Jonathan D.; Milligan, Brian K.; Allard, Lawrence F.; Shin, Dongwon; Shower, Patrick; Chisholm, Matthew F.; Shyam, Amit

doi:10.1016/j.actamat.2020.05.043

Title: The synergistic role of Mn and Zr/Ti in producing θ'/L12 co-precipitates in Al-Cu alloys

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Abstract

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 °C. The addition of Mn in combination with Zr and their segregation to precipitate interfaces play a significant role in stabilizing the metastable θ' precipitates responsible for the alloy's hardness; however, adding Zr and Mn separately only improves the stability to 200 °C and 300 °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 °C and 350 °C, to investigate the role of Zr/Ti in increasing the θ'-precipitate stability. The APT and STEM results reveal that Mn additions stabilize θ' long enough for the slower diffusing Zr atoms to segregate to coherent θ' interfaces that eventually create a θ'/ L1₂-Al₃(Zr_x,Ti_1-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 °C.more »« less

Authors:

^[1]; Milligan, Brian K. ^[2]; Allard, Lawrence F. ^[1];

^[1];

^[1]; Chisholm, Matthew F. ^[1];

^[1]

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Colorado School of Mines, Golden, CO (United States)

Publication Date:: Fri May 22 00:00:00 EDT 2020

Research Org.:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:: USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:: 1649387

Grant/Contract Number:: AC05-00OR22725

Resource Type:: Accepted Manuscript

Journal Name:: Acta Materialia

Additional Journal Information:: Journal Volume: 194; Journal Issue: N/A; Journal ID: ISSN 1359-6454

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; Aluminum alloy; Precipitate stability; Microalloying; Atom probe tomography; Density functional theory

Citation Formats


                    Poplawsky, Jonathan D., Milligan, Brian K., Allard, Lawrence F., Shin, Dongwon, Shower, Patrick, Chisholm, Matthew F., and Shyam, Amit. The synergistic role of Mn and Zr/Ti in producing θ'/L12 co-precipitates in Al-Cu alloys.  United States: N. p., 2020. 
Web.  doi:10.1016/j.actamat.2020.05.043.

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                    Poplawsky, Jonathan D., Milligan, Brian K., Allard, Lawrence F., Shin, Dongwon, Shower, Patrick, Chisholm, Matthew F., & Shyam, Amit. The synergistic role of Mn and Zr/Ti in producing θ'/L12 co-precipitates in Al-Cu alloys.  United States.  https://doi.org/10.1016/j.actamat.2020.05.043

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                    Poplawsky, Jonathan D., Milligan, Brian K., Allard, Lawrence F., Shin, Dongwon, Shower, Patrick, Chisholm, Matthew F., and Shyam, Amit. Fri .  
"The synergistic role of Mn and Zr/Ti in producing θ'/L12 co-precipitates in Al-Cu alloys".  United States.  https://doi.org/10.1016/j.actamat.2020.05.043.  https://www.osti.gov/servlets/purl/1649387.

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@article{osti_1649387,

  title        = {The synergistic role of Mn and Zr/Ti in producing θ'/L12 co-precipitates in Al-Cu alloys},

  author       = {Poplawsky, Jonathan D. and Milligan, Brian K. and Allard, Lawrence F. and Shin, Dongwon and Shower, Patrick and Chisholm, Matthew F. and Shyam, Amit},

  abstractNote = {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 °C. The addition of Mn in combination with Zr and their segregation to precipitate interfaces play a significant role in stabilizing the metastable θ' precipitates responsible for the alloy's hardness; however, adding Zr and Mn separately only improves the stability to 200 °C and 300 °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 °C and 350 °C, to investigate the role of Zr/Ti in increasing the θ'-precipitate stability. The APT and STEM results reveal that Mn additions stabilize θ' long enough for the slower diffusing Zr atoms to segregate to coherent θ' interfaces that eventually create a θ'/ L12-Al3(Zrx,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 °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.},

  doi          = {10.1016/j.actamat.2020.05.043},

  journal      = {Acta Materialia},

  number       = N/A,

  volume       = 194,

  place        = {United States},

  year         = {Fri May 22 00:00:00 EDT 2020},

  month        = {Fri May 22 00:00:00 EDT 2020}

}

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