WELDING RESEARCH ferrite and an increase in Widmanstätten and acicular ferrite. 4. Utilizing the combined models, a process map has been constructed that illustrates the effects of welding speed, separation distance, and laser power on cooling rate and microconstituent volume fractions. Identical cooling rates and microconstituent volume fractions can be obtained with various combinations of process parameters. In general, welding speed and laser power have a more significant effect on cooling rates than separation distance; however, at high welding speeds, the separation distance can be the deciding factor for martensite formation. Acknowledgments The authors would like to thank Mr. Jay Tressler for performing the hybrid welding experiments, Mr. Ed Good and Dr. Jay Keist for assisting with the metallography, and Prof. Lars-Erik Svensson for assisting with the microstructure identification and quantification. 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Welding Journal | April 2015
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