Zinc coatings are one of the major ways to protect steel from corrosion. The inherently brittle and anisotropic nature of zinc, makes it difficult to keep the coating intact, while the steel is formed into its final product. An in depth understanding of the deformation of zinc coatings would therefore help the industry to adapt their processing parameters to obtain more sustainable zinc coatings and therefore increase the longevity of steel.
In our studies we extracted a total of 6 specimens from a zinc coating, with the mean of focused ion beam milling (FIB) in order to perform nano tensile tests [2] (Figure 1b). Four of the specimens are single crystal specimens, while the remaining 2 are bicrystal specimens, which have been extracted from the same grains as the single crystal ones. The in-situ SEM tests were performed to obtain displacement fields, through digital image correlation (InSn speckle pattern size:100 nm, Figure 1a). In combination with the crystal orientation (EBSD), we are able to identify, which slip system was activated in the single and bicrystals, by means of a new slip identification method (called Slip System based Local Identification of Plasticity (SSLIP)) [1].
Our studies revealed that the deformation of zinc can be highly complicated even for the single crystal case, where for instance a succession of interacting deformation mechanisms was observed. Furthermore, the comparison between the single and bicrystal specimens showed that some of the slip systems, which are activating remain active in the bicrystal as well, while others are replaced by newly activating slip systems[3].
References:
[1] Vermeij, T., Peerlings, R. H. J., Geers, M. G. D., & Hoefnagels, J. P. M. (2023). Automated identification of slip system activity fields from digital image correlation data. Acta Materialia, 243, 118502.
[2] Du, C., Maresca, F., Geers, M. G., & Hoefnagels, J. P. (2018). Ferrite slip system activation investigated by uniaxial micro-tensile tests and simulations. Acta Materialia, 146, 314-327.
[3] König,D., Vermeij, T., Maresca, F., & Hoefnagels, J. P. M. (2023) The transition of nanoscale plasticity from single- to bi-crystal tensile tests extracted from a zinc coating. Acta Materialia (Currently in Submission).