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The Effect of Cooling Rate of Friction Stir Welded High Strength Low Alloy Steel

The friction stir welding of steel has produced a hard zone in several different alloys. Despite its detrimental effects on weld toughness, the reasons behind neither its formation nor a method of reducing its size or effects have been explored. Recent advances in process control allow for direct heat input control, which combined with the use of backing plates of different thermal conductivity allows for an expansion of the process window. These control methods also affect the HAZ cooling rate by providing greater range (a 60% increase compared to a fixed backing plate) and control (five welds within 16 °C/s). This increased range produced microstructures consisting of various forms of ferrite at lower cooling rates and bainite at higher cooling rates. The hard zone was determined to be the result of the formation of the bainite at higher cooling rates and was avoided by keeping the cooling rate below 20 °C/s in HSLA-65.

Identiferoai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-5180
Date12 July 2013
CreatorsRose, Scott Anthony
PublisherBYU ScholarsArchive
Source SetsBrigham Young University
Detected LanguageEnglish
Typetext
Formatapplication/pdf
SourceTheses and Dissertations
Rightshttp://lib.byu.edu/about/copyright/

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