Microstructure evolution and mechanical properties of (CoCrNi)90(AlTiZr)5(CuFeMo)5 multicomponent alloy: A pathway through multicomponent alloys toward new superalloys

Thermodynamic criteria of lattice distortion energy (Delta H-el) and enthalpy of mixing (Delta H-max) were considered to design and estimate the initial phase formation and stability in (CoCrNi)(100-x-y)(AlTiZr)(x)(CuFeMo)(y) multicomponent alloy (MCA) system. This study aimed to chase a new alloy design pathway to develop superalloys by benefitting from the concept of multiphase MCAs. The non-equilibrium cast microstructure (CoCrNi)(100-x-y)(AlTiZr)(x)(CuFeMo)(y )displayed a metastable dendritic structure consisting of primary Co-Cr-Ni-rich FCC dendrites and an interdendritic eutectic mixture, comprising supersaturated cubic Laves-phase and FCC phase. The composition of the AB(2)-structure Laves-phase was identified as (Zr, Cr, Cu, Al, Ti)(Ni, Co)(2). Following the short-term annealing, a tenuous network of Zr-rich phase with a cubic structure was formed by the decomposition of the Laves-phase structure. Phase fraction along with the morphology of the intermetallic phase was altered by treatment and eventually semi-circular islands emerged. Results of tensile and compression tests at different strain rates exhibited the detrimental effect of structural instability and dependency of rate-sensitivity to alloy microstructure. Strain-rate increment enhanced the contribution of ductile failure with slip-band indications; however, this was accompanied by activation of further deformation mechanisms and subsequent formability improvement at a higher rate. (C) 2020 Elsevier B.V. All rights reserved.