Crystal plasticity model for single crystal Ni-based superalloys: Capturing orientation and temperature dependence of flow stress

• Published in: International journal of plasticity 2021-02, Vol.137, p.102896, Article 102896
• Main Authors: Gupta, Satyapriya, Bronkhorst, Curt A.
• Format: Article
• Language: English
• Subjects: Anti-phase boundary shearing; Antiphase boundaries; Back stress; Chemical precipitation; Crystal dislocations; Crystal plasticity; Crystal structure; Deformation mechanisms; Dislocation density; Model testing; Ni-based superalloys; Nickel; Nickel base alloys; Optimization; Orientation; Plastic properties; Precipitates; Room temperature; Shearing; Single crystals; Slip resistance; Strengthening; Stress-strain curves; Superalloys; Temperature dependence; Yield strength; Yield stress; γ − γ′microstructure
• ISSN: 0749-6419; 1879-2154
• DOI: 10.1016/j.ijplas.2020.102896

We develop a dislocation density based crystal plasticity model to capture the micromechanical behavior of γ′ strengthening nickel-based superalloys. The elasto-viscoplastic model presented here accounts for hardening behavior of both γ and γ′ which are the two phases considered in the present work. The model includes multiple strengthening mechanisms such as Orowan stress, evolving slip resistance caused by dislocation interactions, and γ′ structural contribution to initial slip resistance. Interaction between γ and γ′, a key feature of these alloys has been modelled in terms of back stress induced by dislocation pileup or looping around the large γ′ precipitates. Furthermore, anti-phase boundary (APB) shearing is considered as the dominant deformation mechanism for shearable γ′ precipitates. In addition to octahedral {111}⟨110⟩ slip, the model also accounts for cube slip systems {100}⟨110⟩ which are known to be instrumental in γ′ shearing and introducing flow stress orientation dependence. Temperature dependence of the initial slip resistance is fitted against experimental observation of anomalous yielding for two different single crystal orientations. An optimization procedure based on the minimization of the error between simulated and experimental stress strain curves, is adopted to evaluate a selected group of material parameters. Subsequently, proper working of the model is tested against an independent set of single crystal experimental data available for CMSX-4 around service temperature and MD2 at room temperature. The model also represents a strong orientation dependence of yield stress anomaly (YSA), a salient feature of Ni-based superalloys. •A dislocation density based crystal plasticity model for γ – γ' microstructure Ni-based superalloys is developed where separate flow rules for each of the γ – γ' phases is proposed.•Mechanism based modeling of γ and γ' phases allows for accurate prediction of singlsin experimental observations for single crystals of Ni-based superalloys covering RT to 1150 C).•Temperature dependent predictions of CMSX-4 flow stress suggests the presence of strong orientation dependence with flow stress increase with temperature for some orientations.