Microstructural stability and mechanical properties of equiatomic CoCrCuFeNi, CrCuFeMnNi, CoCrCuFeMn alloys

The microstructural stability and mechanical properties of CoCrCuFeNi, CrCuFeMnNi and CoCrCuFeMn alloys in which one element was substituted by Cu from CoCrFeMnNi high entropy alloy were studied. The separation of solid solution phase into various solution phases and/or intermetallic phases were observed to have a great influence on the deformation mechanisms. CoCrCuFeNi alloy exhibited excellent deformability with low flow stress (276 MPa) and the saturation of flow stress at 543 MPa. The good deformability of CoCrCuFeNi in the present study is attributed to the presence of two separated ductile FCC phases. CrCuFeMnNi exhibited the high yield stress (793 MPa) and it was deformed up to the true strain of 1.0 without crack formation to reach the flow stress as high as 1100 MPa. The high flow stress in CrCuFeMnNi alloy is associated with the role of Cr-Fe dendritic particles which act as obstacles to slip in the matrix. CoCrCuFeMn exhibited the yield stress as high as 805 MPa, but fractured at the true strain of ∼0.3, which is associated with the presence of vertical cracks in brittle σ phase grains.