Modelling of cyclic plasticity and crack-tip deformation in a single crystal nickel-based superalloy

In this paper, cyclic plasticity in a single crystal nickel-based superalloy CMSX4 at elevated temperature was modelled using crystal plasticity (CP) and discrete dislocation dynamics (DDD). The CP modelling was carried out at the continuum level based on shear deformation along the octahedral slip systems. The DDD approach was implemented for a representative volume element with periodical boundary conditions. The DDD model parameters were calibrated using the predicted response by the CP model. The obtained numerical results by the two models compared with each other under strain-controlled monotonic and cyclic loading conditions in both <001> and <111> orientations. The CP model was further applied to study crack-tip deformation under fatigue loading. Stress-strain responses, as well as stress and strain distributions, near the crack tip were particularly monitored to assess the role of cyclic plasticity in controlling fatigue-crack propagation. The work has applications in life assessment of nickel-based superalloy components for high-temperature applications