Papers by Author: Murray Mahoney

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Authors: Christopher B. Smith, Arun Mohan, Rajiv S. Mishra, Murray Mahoney, Mike Miles, Scott M. Gillis, Lee M. Cerveny, Gerald Opichka
Abstract: The use of friction stir processing (FSP) on marine grade aluminum sheet has been investigated with the objective of locally enhancing the material properties. This can potentially allow low cost commercial grade aluminum to be used in superplastic forming applications or further enhance the formability to allow more complex geometries to be formed. FSP has been demonstrated to enable superplasticity (uniform elongations >250%) in 5083-H116 over a range of friction stir processing conditions.
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Authors: Murray Mahoney, Sam Sanderson, Peter Maak, Russell Steel, Jon Babb, Dale Fleck
Abstract: Friction Stir Welding (FSW) is being investigated as a method to fabricate a partial penetration closure weld of the steel vessel of a copper-coated used fuel container. The hemi-head is made of A516 Grade 70 steel and the cylinder body is made of A106 Grade C steel. In this initial feasibility study, the objective is to use FSW to demonstrate the merits of FSW using flat steel plate in concert with a closure weld joint designed specifically for a cylindrical container. To complete this objective, there are two initial feasibility demonstrations. First, demonstrate the capability of FSW to create defect free welds in a corner joint design with specific dimensions (10 mm deep weld nugget). Subsequently, verify the weld quality by ultrasonic inspection and metallography. Further, characterize weld zone properties by establishing mechanical properties and hardness at room temperature, and impact toughness at-5°C. Second, demonstrate the ability to use FSW to repair defects that might occur in the initial friction stir weld. Weld repair was accomplished by intentionally creating tunnel defects by FSW, performing metallography and ultrasonic inspection to characterize the morphology of the defects, performing a second friction stir weld repair over the defects, and verifying the subsequent weld integrity by repeating the metallography and ultrasonic inspections. Results on these initial two phases of this program are presented herein.
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Authors: Murray Mahoney, Tracy W. Nelson, Carl Sorenson, Scott Packer
Abstract: Friction stir welding (FSW) offers many potential benefits including reduced distortion, lower cost, no harmful airborne emissions, semi-automated, etc. Although initially developed for Al alloys, considerable work now has been completed to explore the ability of FSW to weld relatively thin (6 mm) ferrous alloys including many alloys of interest to the ship building industry such as HSLA-65. The status of current progress for ferrous alloys is presented offering insight into capabilities and opportunities as well as areas of FSW activity requiring additional improvement. Practical issues of weld penetration depth, gap tolerance, post-FSW mechanical properties, and distortion are addressed. Special consideration will be made to address the ability to friction stir weld 6 mm thick HSLA-65 steel with no/low distortion. Tool materials discussed will include polycrystalline cubic boron nitride (PCBN) and a new composite tool fabricated from PCBN and W-25Re. Last, data will be presented illustrating the complete absence of harmful airborne emissions when welding an austenitic stainless steel.
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