Butt-joint seam of a high entropy alloy (HEA) of the CoCrFeNiMn system was successfully obtained by friction stir welding (FSW). The HEA was produced by self-propagating high-temperature synthesis. Along with the principal elements, a small amount (0.9 at.%) of C was added to the alloy. The as-cast alloy was cold rolled and annealed at 900°C to produce refined microstructure. The structure of the annealed alloy consisted of a recrystallized face-centered cubic matrix with a grain size of 9.2 μm and fine Cr-rich M 23 C 6 carbides. FSW of the HEA resulted in microstructure refinement to d = 4.6 μm in the stir zone. A noticeable rise in strength and some decrease in ductility of the processed alloy in comparison with the initial condition can be associated with the microstructure refinement and some increase in the volume fraction of M 23 C 6 carbides.
In this work, a structural response of 6061-T6 aluminum alloy to friction-stir welding (FSW) was studied in wide range of processing conditions in order to establish a better foundation for the microstructure-strength relationship in produced welds. In contrast to the widely-accepted conception of the FSW-induced precipitation behavior, the welding temperature was found to be often below the dissolution threshold and thus no particle dissolution took place. Moreover, the peak temperature never exceeded 500 � C, and therefore the particles never dissolved completely. Considering a relatively low cooling rate measured in the stir zone, the dissolved precipitates were suggested to partially re-precipitate as solute clusters during weld cooling cycle thus imparting a substantial hardening effect. Accordingly, the precipitation coarsening was deduced to be the major softening mechanism. Due to the extreme sensitivity of this process to a duration of the weld thermal cycle, the welding speed was surmised to be the key factor controlling weld strength.
Laser beam welding and friction stir welding of high entropy alloys (HEA) of the CoCrFeNiMn system were studied. The HEAs were produced by self-propagating high-temperature synthesis (SHS). Along with the principal elements, Al, C, S, and Si impurities were detected in the composition of the alloys. The as-cast alloys consisted of columnar fcc grains with coarse precipitates of MnS and fine Cr-rich M23C6carbides. Laser beam welding resulted in the formation of a defect-free weld joint. Precipitation of nanoscale B2 phase particles in the weld zone leaded to a pronounced increase in microhardness from ~150 HV of the base material to ~220 HV in the fusion zone. Friction stir welding (FSW) of a recrystallized state of the HEA with the average grain size of 3-5 μm resulted in the formation of a fine microstructure with a grain size of ~1.5 μm in the most strained area. Noticeable rise in strength and some decrease in ductility of the processed alloy in comparison with the initial condition can be associated with the formation of nanosized M23C6carbides.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.