Edge-Cracking Behavior of CoCrFeMnNi High-Entropy Alloy During Hot Rolling

This work investigated edge-cracking behavior of equiatomic CoCrFeMnNi high-entropy alloy during hot rolling at rolling temperatures 500 ≤ TR ≤ 1000 °C. Edge cracks did not form in the material rolled at 500 °C, but widened and deepened into the inside of plate as TR increased from 500 °C. Edge cracks were most severe in the material rolled at 1000 °C. Mn–Cr–O type non-metallic inclusion and oxidation were identified as major factors that caused edge cracking. The inclusions near edge region acted as preferential sites for crack formation. Connection between inclusion cracks and surface cracks induced edge cracking. Rolling at TR ≥ 600 °C generated distinct inclusion cracks whereas they were not serious at TR = 500 °C, so noticeable edge cracks formed at TR ≥ 600 °C. At TR = 1000 °C, significant oxidation occurred at the crack surface. This accelerated edge crack penetration by embrittling the crack tip, so severe edge cracking occurred at TR = 1000 °C.