Phase-field, dislocation based plasticity and damage coupled model: modelling and application to single crystal superalloys

TL;DR

This paper introduces a comprehensive coupled model integrating phase-field, dislocation density plasticity, and damage mechanics to simulate and analyze the creep behavior of single crystal superalloys, capturing complex dislocation phenomena.

Contribution

The novel model effectively couples dislocation dynamics, phase evolution, and damage, solving the 'swallow-gap' issue and simulating dislocation interactions with the second phase during creep.

Findings

Simulated microstructures match experimental observations.

The model captures dislocation cutting into the second phase during tertiary creep.

Creep properties from simulations agree with experimental data.

Abstract

In the present work, we propose a novel model coupling phase-field, dislocation density based plasticity and damage. The dislocation density governing equations are constructed based on evolutions of mobile and immobile dislocations. Mechanisms including dislocation multiplication, annihilation, mobile-immobile transfer due to dislocation interactions and block of interfaces are incorporated in the model. Especially, the "swallow-gap" problem surrounding the coarsened second phase, which often appears in dislocation and phase-field coupled simulations, is solved in the present model. Moreover, the phenomenon of dislocation cutting into the second phase during tertiary creep, which has rarely been considered in previous phase-field simulations of single crystal superalloys, is successfully captured in the present model with the coupling of damage. The long range stresses induced by external loading, coherent interface misfit, plastic activity and damage, as well as the short range stresses induced by antiphase boundary, dislocation line tension and forest dislocation trapping are considered in the dynamics of the model. High temperature $\langle 001 \rangle$ creep simulations of single crystal superalloys under 200 MPa and 350 MPa are conducted using the coupled model and compared with experiments. The results show that simulated phase microstructures, dislocations and creep properties principally agree with experiments during the whole creep stage, in terms of both microscopic and macroscopic features.