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Neilson Dissertation Final.pdf (31.56 MB)

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Mechanical Behavior and Microstructural Evolution during Hot Deformation of Aluminum 2070

Neilson, Henry Jathuren
http://rave.ohiolink.edu/etdc/view?acc_num=case152302739582634

Abstract Details

2018, Doctor of Philosophy, Case Western Reserve University, Materials Science and Engineering.
A third generation Ag-free Al-Li alloy, 2070, is the focus of this dissertation. To determine its suitability for a range of applications, this alloy was first qualified through a series of room temperature mechanical tests. Samples from each orientation (e.g., L, T, or S) were excised from each section of an H-forging to determine the effects of prior work and degree of anisotropy. Samples were then tested at room temperature in tension, compression, and Charpy impact. Room temperature mechanical behavior of as-received H-forgings of 2070 was found to meet or exceed properties of second and third generation Al-Li alloys. The primary focus of this dissertation was to determine the effects of forging conditions (i.e., temperature and strain rate) on flow stress and microstructural evolution during/after hot deformation of this material. Subscale right circular cylinder samples were deformation processed under isothermal conditions at a range of temperatures (T = 300/425/450/475°C) and strain rates (0.01/s, 0.1/s, 5.0/s) to 100% true strain in order to determine these effects on the resulting flow stress and microstructure. Activation energy and power dissipation coefficients were determined for each temperature and strain rate combination followed by microstructure analyses via optical and scanning electron microscopy (SEM). Microstructure analyses included EBSD (electron backscatter diffraction) to determine the degree of dynamic recrystallization (DRX) or dynamic recovery (DRV) present after deformation processing at different temperatures and strain rates. Dynamic recovery was found to be the dominant deformation mechanism for the sample tested at 450°C and 0.01/s. Samples tested at 450°C and 5.0/s or 300°C and any strain rate (0.01, 0.1, or 5.0/s) were found to be dominated by dynamic recrystallization, with a large area fraction of unresolved highly deformed grains. When samples were solution heat treated (at 510°C for 1 hour) after deformation processing, the sample processed at 450°C and 0.01/s was found to have little microstructural change, while the sample processed at 300°C and 5.0/s showed substantial static recrystallization.
John Lewandowski (Committee Chair)
Gerhard Welsch (Committee Member)
Jennifer Carter (Committee Member)
Sunniva Collins (Committee Member)
235 p.
Materials Science
Hot deformation; aluminum; lithium; processing; forging; microstructural analysis; mechanical behavior; materials science

Recommended Citations

Citations

  • Neilson, H. J. (2018). Mechanical Behavior and Microstructural Evolution during Hot Deformation of Aluminum 2070 [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case152302739582634

    APA Style (7th edition)

  • Neilson, Henry. Mechanical Behavior and Microstructural Evolution during Hot Deformation of Aluminum 2070. 2018. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case152302739582634.

    MLA Style (8th edition)

  • Neilson, Henry. "Mechanical Behavior and Microstructural Evolution during Hot Deformation of Aluminum 2070." Doctoral dissertation, Case Western Reserve University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case152302739582634

    Chicago Manual of Style (17th edition)

case152302739582634
205
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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.