Modelling the effect of macro-segregation on the fracture toughness of heavy forgings using FFT based crystal plasticity simulations

Sicong C. Ren (Corresponding Author), Bernard Marini, Pierre Forget

Research output: Contribution to journalArticleScientificpeer-review

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The local approach has been successful in evaluating the brittle fracture probability of nuclear pressure vessel steels by establishing a link between microstructural defects and the macroscopic fracture behaviour. The evaluation of fracture probabilities relies on the applied stress on the smallest representative elementary volume. A proper description of the stress heterogeneities in polycrystals helps refine the prediction. The current work investigates the effect of carbon macro-segregation in heavy forgings and demonstrates a workflow combining crystal plasticity with the Microstructure Informed Brittle Fracture (MIBF) local approach model in fracture toughness prediction. The microstructural and mechanical properties of low alloy steels with different segregation levels were evaluated. A dislocation-density based crystal plasticity model which contains carbide strengthening contribution was identified and applied for modelling microstructure influence on local stress distributions. Results show that the microstructural evolution observed at high carbon levels has a significant influence on local stress distributions, which in turn affects the fracture toughness. The simulation results also demonstrate that, with proper input of microstructural information, the MIBF model is capable to predict the shift of the brittle-to-ductile transition zone with the variation of carbon and alloying elements and gives insights about factors affecting the resistance of materials.
Original languageEnglish
Article number108694
JournalEngineering Fracture Mechanics
Publication statusPublished - Sept 2022
MoE publication typeA1 Journal article-refereed


This work was initiated and partially funded within the framework of a CEA-EDF-Framatome joint project. The authors want to acknowledge their support related to experimental characterizations and model framework. Special thanks to A. Gangloff (CEA) for EBSD and carbide analysis, E. Pons (CEA) for mechanical testing, C. Toffolon-Masclet (CEA) for Thermalcalc calculations and L. Vincent (CEA) for fruitful discussions about the present results. The authors have also received funding from the EU Euratom Research and Training Programme ENTENTE project [grant number 900018] related to the development of modelling techniques based on measured microstructures and the fracture toughness predictions with MIBF model used in this work.


  • crystal plasticity
  • macro-segregation
  • FFT method
  • cleavage
  • fracture toughness


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