Friction stir welding of a carbon-doped CoCrFeNiMn high-entropy alloy

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 mu m and fine Cr-rich M23C6 carbides. FSW of the HEA resulted in microstructure refinement to d = 4.6 mu m 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 M23C6 carbides.