Effects of (W, Cr) carbide on grain refinement and mechanical properties for CoCrFeMnNi high entropy alloys

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>In this study, we investigated the influence of (W, Cr) carbide on the hardness and tensile properties of friction stir welds (FSWs) for CoCrFeMnNi high entropy alloys. FSW without cracks or voids were achieved for rotational speeds of 400–1000 rpm. As the rotational speed increased, the thinning of the weld thickness compared to the thickness of the base metal was increased. Specifically, an abnormal tornado-shaped region was observed in the stir zone at rotation speeds of 600 rpm and above. The tensile strength increased as the rotation speed increased from 400 to 800 rpm and decreased at a rotation speed of 1000 rpm. The abnormal region with a fine (W, Cr) carbide of 0.5 μm or less was dispersed in the grain boundaries. At a rotation speed of 800 rpm, the dispersion of fine (W, Cr) carbide was optimized to produce grain refinement and maximum tensile strength. However, at 1000 rpm, (W, Cr) carbide coarsened due to high heat input, and the number of carbide particles per unit area decreased, thereby decreasing the hardness and tensile strength.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Friction stir welds without crack or void were achieved for CoCrFeMnNi alloy. </LI> <LI> Fine (W, Cr) carbides of 0.5 μm or less were dispersed in the grain boundaries. </LI> <LI> Dispersion of fine carbides produced grain refinement and maximum tensile strength. </LI> <LI> High heat input decreased the number of carbides per unit area. </LI> <LI> High heat input coarsened (W, Cr) carbides, thereby decreasing the tensile strength. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>