Thermal stability of nanocrystalline CoCrFeNi multi-principal element alloy: Effect of the degree of severe plastic deformation

The effect of the degree severe plastic deformation (SPD) on thermal stability a nanocrystalline CoCrFeNi multi-principal element alloy was studied. SPD method high-pressure torsion (HPT) utilized to achieve microstructure. structural investigated near centers and edges HPT-processed disks deformed for ½, 1, 5 10 turns. For almost all studied samples, two exothermic peaks in temperature ranges 600–750 750–950 K were observed by differential scanning calorimetry (DSC) between room 1000 K. saturation released heat value first DSC peak about 4 J/g that achieved at shear strain ∼200. second peak, saturated 20 with 6–7 J/g. It revealed is related annihilation dislocations low deformation. At same time, edge parts processed one or higher numbers turns vacancy has also major contribution peak. annihilated concentration estimated from (0.6–0.9) × 10−3. disappearance grain boundaries due recrystallization remaining dislocations. MPEA samples exhibited very high hardness values 4000 5100 MPa, depending number location along disk radius. decreased only during when occurred.