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Effect of friction stir welding conditions on properties and microstructures of high strength automotive steel

Abstract The use of high strength steels (HSS) and ultra high strength steels (UHSS) is increasing in automotive applications to reduce vehicle weight and to improve structural performance. This study focused on the properties and microstructures of friction stir welded steel sheets, as a function of welding conditions. Tooling feeds and speeds had a significant impact on mechanical properties and microstructures of the welds. For example, at constant tool speeds higher feedrates produced softer welds with large amounts of primary ferrite, compared with lower feedrates which produced harder welds and a greater fraction of martensite. These results illustrate the potential of adjusting weld properties and microstructures by using different friction stir welding process conditions for HSS and UHSS alloys.