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In-situ Radiography of Hydrogen Porosity Growth and Development in Aluminum Welds.

Barraza, Alexyia Marie
http://orcid.org/0000-0002-0499-9902
http://rave.ohiolink.edu/etdc/view?acc_num=osu1620822768668166

Abstract Details

2021, Master of Science, Ohio State University, Welding Engineering.
In aluminum welding, hydrogen contamination is the main cause of the welding defect, porosity. Porosity in welds can adversely affect the mechanical properties such as tensile strength, fatigue life and ductility. There have been a variety of solutions to help reduce porosity in aluminum welds including finding the source of hydrogen. However, in some cases the amount of hydrogen may be drastically reduced but impossible to completely eliminate. Another approach to this issue is to understand where a pore originates and how it moves and grows within the weld pool. This information may lead to a more innovative method for pore elimination during gas tungsten arc (GTA) welding of aluminum. In-situ aluminum weld experiments were set-up to observe the porosity formation in aluminum welding. Aluminum alloys 1100, 4047, and 6061 were autogenously gas tungsten arc welded in a chamber while real-time digital radiography was performed. Hydrogen was added in parts-per-million through an argon-hydrogen shielding gas. The shielding gas hydrogen was varied between 0 and 1000 ppm of hydrogen and three travel speeds were tested: 1.69 mm/s, 2.54 mm/s and 3.39 mm/s. The smallest pore measured was roughly 90μm, demonstrating this method of insitu observation to be a useful way to monitor macro-porosity in aluminum welds. Micro-pores could be seen near the surface of weld pool but it was difficult to see their shape or movement. The amount of hydrogen added through the shielding gas played an important role in macro-pore growth and well as travel speed. Pore growth rate increased with increase in hydrogen saturation and slower travel speed. In Alloy 1100 macro-pores originated at the bottom of the weld pool, near the trailing portion of the weld pool in an elliptical shape. Macro-pores in Alloy 6061 originated at the leading edge of the weld pool, near the surface. Once the macro-pores reached a favorable size, they were then swept back to the trailing edge of the weld pool. A single macro-pore was observed during welding of Alloy 4047 indicated pore formation and movement similar to that of the macro-pores in Alloy 6061. Regardless of Alloy, macro-porosity remained on the outer “still” fusion boundary of the weld pool. Pores did not enter the bulk of the weld pool. Pore movement upward is influenced by buoyancy and fluid flow. Micro-pores became fully engulfed with periodic oscillation of the weld pool leading to banding. The banding followed the shape of the weld pool. In Alloy 1100, when macro-pores were partially engulfed, this resulted in elliptical-shaped pores growing in the direction of the weld. Macro-pores in Alloy 6061 were not partially engulfed; when they were fully engulfed the macro-pores remained circular in shape.
Carolin Fink, PhD (Advisor)
Boian Alexandrov, PhD (Committee Member)
Carl Cross, PhD (Advisor)
116 p.
Materials Science
aluminum porosity; in-situ welding

Recommended Citations

Citations

  • Barraza, A. M. (2021). In-situ Radiography of Hydrogen Porosity Growth and Development in Aluminum Welds. [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1620822768668166

    APA Style (7th edition)

  • Barraza, Alexyia. In-situ Radiography of Hydrogen Porosity Growth and Development in Aluminum Welds. 2021. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1620822768668166.

    MLA Style (8th edition)

  • Barraza, Alexyia. "In-situ Radiography of Hydrogen Porosity Growth and Development in Aluminum Welds." Master's thesis, Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1620822768668166

    Chicago Manual of Style (17th edition)

osu1620822768668166
322
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