Papers by Author: Paul Edwards

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Authors: Paul Edwards, Todd Morton, Gregory L. Ramsey
Abstract: Laser Beam Welding of ATI 425® Alloy was performed on 2.5 mm thick butt joints. This new alloy could be used in place of standard Ti-6Al-4V for a variety of lower-cost structural solutions. Demonstration of its fusion weldability with laser welding is of particular interest because it is a near-net- shape process, capable of high welding speeds, which will further enable lower cost manufacturing options. It was found that ATI 425® Alloy could be successfully welded using a fiber laser at speeds over 3 m/min. Microstructural, microhardness and tensile property evaluations were performed on the resulting welds. It was found that there was a 15% hardness increase in the weld and the strength of the joints was within 2% of base metal properties.
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Authors: Paul Edwards, Marc Petersen, Mamidala Ramulu, Rodney Boyer
Abstract: Heat treatment processes for standard fusion welding techniques in titanium are well established, but the optimal heat treatment for Friction Stir Welded titanium has not been evaluated. In this study, 6 mm thickness titanium 6Al-4V butt welds were subjected to heat treatments ranging from 700 to 900 C. Results of the metallographic analysis for each heat treatment condition will be presented in addition to microhardness, tensile and fatigue properties. It was found that increased heat treatment temperatures lead to lower hardness and tensile strengths, higher elongation to failure and improved high cycle fatigue performance. Furthermore, fracture toughness and crack growth tests were performed for welds subjected to a standard post-weld stress relief. The fracture toughness was lower than the parent material, but crack growth rates in the weld were similar to that of the base metal.
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Authors: Daniel G. Sanders, Paul Edwards, Mamidala Ramulu, Glenn Grant
Abstract: In friction stir welding (FSW), the semi-circular shaped FSW pin tool feed marks that are left behind varied in depth and shape which are detrimental not only in fatigue performance but also in further processing such as superplastic forming (SPF). Experimental investigation was conducted to determine the effects of changes to the FSW process parameters on the surface roughness of the weld of fine grain 2 mm thick titanium alloy, Ti- 6Al-4V. In addition to optimizing the surface texture of the welds, the superplastic performance of the weld nugget was made to be equal to the superplasticity of the parent metal by altering the spindle speed and feed rate used during FSW to identify the quality in terms of cold weld or hot weld. FSW process conditions of spindle speed of 500 RPM and a feed rate of 150 mm/min was found to produce a uniform deformation in both weld and parent metal when the joint was superplastc formed.
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Authors: Paul Edwards, Mamidala Ramulu, Daniel G. Sanders
Abstract: Friction Stir Welding of Ti-6Al-4V was performed on 5 mm thickness plate in order to assess the affect of welding conditions on the resulting microstructure and superplastic forming behavior of the joints. A variety of welding conditions were tested and all welds were subsequently Superplastically formed. It was found that the weld parameters do influence the microstructure and degree of superplastic performance of the joints. Spindle speed was found to have the most dominant affect on the resulting microstructure and superplastic forming behavior. Low spindle speed welds lead to fine grained microstructures and highly superplastic welds, relative to the base material, while high spindle speed welds larger grained microstructures and less superplastic welds.
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