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Simulation of Solid-State Weld Microstructures in Ti-17 via Thermal and Thermo-Mechanical Exposures

Orsborn, Jonathan L
http://rave.ohiolink.edu/etdc/view?acc_num=osu1461169454

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
Solid-state welding processes are very important to the advancement of aviation technology; since they enable the joining of dissimilar metals without the additional weight and bulk of fastening systems, the processes can create for stronger and lighter parts to increase payload and efficiency. However, since the processes are not equilibrium, not much is understood about what happens to the materials during the process. During a solid-state weld, the materials being welded are exposed to rapid heating rates, high maximum temperatures, large and varying amounts of deformation, short hold times at temperature, and fast cooling rates. Due to the dynamic nature of the process it is very hard to measure the strains and temperatures experienced by the materials. This work attempted to simulate the microstructures observed in solid-state welds of Ti-5Al-2Sn-2Zr-4Cr-4Mo, or Ti-17. If the microstructures could be replicated in a controlled and repeatable fashion, then perhaps the conditions of the welding process could be indirectly determined. The simulations were performed by rapidly heating Ti-17 specimens, holding them for a very short time, and rapidly cooling. Some of the samples were also subjected to deformation while at high temperatures. The microstructures resulting from the thermal and thermo-mechanical exposures were then compared with microstructures from an actual solid-state weld of Ti-17. It was determined that the presence of untransformed secondary alpha indicates the temperature did not exceed the beta transus of the alloy (~900 °C), the presence of untransformed primary alpha indicates that the temperature did not exceed ~1100 °C, homogenized beta grains indicate that the temperature did exceed 1100°C, and the presence of ghost alpha is indicative that the temperature likely exceeded ~950 °C. These numbers are rough estimates, as time at temperature and heating rate both factor into the process, and shorter times at higher temperatures can sometimes produce results similar to longer times at lower temperatures. It was also determined that ghost alpha is a conglomeration of alpha laths with many different morphological orientations and crystallographic orientations, with beta present between the laths.
Hamish Fraser (Advisor)
Stephen Niezgoda (Committee Member)
Antonio Ramirez (Committee Member)
318 p.
Materials Science
Solid-State Welding; Ti-17; Linear Friction Welding; Ghost Alpha; Microstructure Evolution

Recommended Citations

Citations

  • Orsborn, J. L. (2016). Simulation of Solid-State Weld Microstructures in Ti-17 via Thermal and Thermo-Mechanical Exposures [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461169454

    APA Style (7th edition)

  • Orsborn, Jonathan. Simulation of Solid-State Weld Microstructures in Ti-17 via Thermal and Thermo-Mechanical Exposures. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1461169454.

    MLA Style (8th edition)

  • Orsborn, Jonathan. "Simulation of Solid-State Weld Microstructures in Ti-17 via Thermal and Thermo-Mechanical Exposures." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461169454

    Chicago Manual of Style (17th edition)

osu1461169454
293
© 2016, some rights reserved.Creative Commons License Simulation of Solid-State Weld Microstructures in Ti-17 via Thermal and Thermo-Mechanical Exposures by Jonathan L Orsborn is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.