Understanding plasticity of pearlitic nanolamellar structures through a simple material modelWednesday (26.09.2018) 17:15 - 17:30 S1/01 - A1 Part of:
Pearlitic steels are among the strongest metallic bulk materials, reaching up to 7 GPa of tensile strength. The strengthening mechanisms of pearlitic steels are closely related to its lamellar structure that evolve with monotonic deformation to a very fine nanolamellar structure. A very simple two-phase continuum anisotropic elasto-plastic model that accounts for the microstructural evolution and mechanical behaviour of this lamellar structure has been developed and validated up to large strains and for different strain paths. The model takes into account different strengthening mechanisms including the dependence on pearlitic spacing (arising from the confined slip of dislocations in the ferritic lamellae) and the strengthening from the evolving intralamellar dislocation density. Cementite phase is assumed to behave as elastic perfectly plastic material. In spite of the simplicity of the model, it naturally captures the macroscopic anisotropy and the internal microstresses developed due to the different mechanical behaviour of both phases. Moreover, the model helps understand the nature of the strain hardening mechanisms that occur up to moderate/large deformations (before cementite dissolution). The model also captures the plastic instability due to kinking of the lamellar structure and shear band formation. The model is applied to simulate the compression of single colony micropillars with different orientations and the results are compared to the experimental results obtained by the group of Prof. R. Pippan (Acta Materialia 106, pp. 239-248, 2016).