Investigation of damage mechanisms related to microstructural features of ferrite-cementite steels via experiments and multiscale simulations

• Published in: International journal of plasticity 2023-11, Vol.170, p.103745, Article 103745
• Main Authors: Wang, Huiling, Wang, Feng, Qian, Dongsheng, Chen, Fei, Dong, Zhaohua, Hua, Lin
• Format: Article
• Language: English
• Subjects: Cohesive zone model (CZM); Crystal plastic finite element method (CPFEM); Damage mechanism; In situ tensile test; Molecular dynamics (MD); Representative volume element (RVE); Spheroidized ferrite-cementite (SFC) steel
• ISSN: 0749-6419; 1879-2154
• DOI: 10.1016/j.ijplas.2023.103745

•Microscopic damage process and mechanism in spheroidized ferrite-cementite steel were investigated using in situ test and representative volume element method.•There are three damage mechanisms in spheroidized ferrite-cementite steel under uniaxial tension: cementite cracking, ferrite/cementite interface debonding, and ferrite cracking.•Three types of voids are driven by the maximum principal stress in the cementite, the maximum normal stress at the ferrite/cementite interface, and the plastic strain within the matrix phase, respectively.•A strong dependence was found between void initiation and ferrite orientation, local misorientation, cementite morphology, and ferrite grain boundary arrangement. Spheroidized ferrite-cementite steel (SFC) is susceptible to micro-defects owing to the mismatched deformation between the ferrite and cementite during cold forming, which seriously deteriorates the fatigue life. However, the damage mechanism related to microstructural features in the SFC steel during cold deformation has not been fully investigated, hindering control of the microstructure and forming process. This study presents a method coupled with experiments and multiscale simulations to research the damage mechanisms and the dependence of microstructure features under uniaxial tension in SFC steel. In situ tensile test revealed three damage mechanisms in SFC steel under uniaxial tension: cementite cracking, ferrite/cementite interface debonding, and ferrite cracking. In particular, the final fracture was mainly dominated by the ferrite/cementite interface debonding. In multiscale simulations, the macroscale tensile and nanoindentation simulations were carried out to obtain the strain history and mechanical properties of the mesoscale simulations, respectively. The mesoscale IP-based RVE and CP-based unit cells simulations were performed to capture the driving forces from the three damage mechanisms and the dependence of microstructural features, respectively. The nanoscale molecular dynamics simulation was conducted to identify the model parameters of cohesive zone model (CZM) in the mesoscale simulations. The numerical results indicated that particle-cracking void occurred when the internal von Mises stress exceeded the ultimate strength of the cementite particles. Interface-debonding void nucleated when the load on the particle was insufficient to resist its strength. Matrix-cracking should be attributed to the stress concentration caused by the disloca