Crystal plasticity phase-field simulation of slip system anisotropy during creep of Co-Al-V monocrystal alloy under multidirectional strain

Abstract

The preferable thermodynamic stability of L12 γ'-Co3(Al, V) phase and wide γ+γ' two-phase region endow the Co-Al-V alloy with great application potential. By introducing the digitized image of SEM morphology into phase-field simulation, utilizing the sublattice free energy model and the crystal plasticity strain model to simulate the anisotropic slip system, the rafting behaviors of the L12 γ'-Co3(Al, V) phase and the creep properties of Co-5Al-14V (at.%) alloy under tensile, compressive, shear, and monoclinic strains are studied. The partitioning ratio of element and orientation degree of γ' phase indicate that the uniaxial compressive strain improves the microstructural stability and the creep resistance at early creep stage. The creep resistance of alloy in state of equilibrium volume fraction of γ' phase is superior to that in the nonequilibrium volume fraction, and the creep resistance increases in order of tensile strain, compressive strain, and shear strain. Additionally, the dominant octahedral slip systems in fcc structure are (1¯1¯1)[101] under tensile strain, (1¯11)[01¯1] under compressive and 15° monoclinic strains, and (1¯1¯1)[1¯10] under 45° monoclinic strain. The hardening effect is prominent in γ matrix, and the high average critical resolved shear stress leads to the low creep strain. This study reveals the correlations between the slip system anisotropy and creep behaviors of Co-Al-V alloy under external strain, and also provides a method to combine the phase-field simulation with the experimental image for predicting the morphology evolution.