Speaker
Description
Due to an outstanding combination of hardness and toughness, the WC-Co hard metal is successfully used in many applications and is considered one of the most important composites in engineering. Nevertheless, recently there has been significant advances achieved in its performance as micromechanical tests have facilitated a better design. A particularly useful technique applied to the WC-Co, is the micropillar compression. It permits the identification and analysis of different deformation and failure mechanisms, such as the activation of slip systems, interface gliding and crack initiation. However, the material response could easily be dominated by many test variables, such as sample geometry, indenter misalignment, contact friction, local variability of phase composition, residual stresses, substrate and indenter deformation, etc. To remedy these shortcomings, FEM analyses can be used which would allow a better interpretation of the experimental results. However, until now, numerical simulations of WC-Co have been mostly limited to (i) 2D and 2.5D reconstruction of real WC-Co microstructure, which are inappropriate for micropillar compression simulations; and (ii) synthetic (via tessellation algorithms) 3D reconstruction of WC-Co microstructure. In this work, we use FIB tomography to reconstruct a real 3D microstructure of the WC-Co and then perform micropillar compression simulations, with the aim of quantifying the uncertainties related with this type of experiment. Finite strain isotropic crystal plasticity and microplane models have been used for the metallic (ductile) phase and the hard (brittle) ceramic phase, respectively. Results show the importance of the test geometry as well as the percentage of metallic binder. For high metallic binder content plastic failure dictates the response, while for low metallic binder the response is governed by microcracking. These results help understand better the micromechanics of these engineering materials.
| Speaker Country | Brazil |
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