Texture and Microstructure Control in Zinc Coated Steel Sheets. Effect on Formability of the Coatings

Many commercial galvanised steel sheets have been characterised before deformation (grain size, grain distribution in the coatings, pre-cracking, individual orientations, misorientations between neighbouring grains, local and global textures) in connection with the zinc alloy which was used and the process parameters.The samples were bent by a biaxial expansion and examined afterwards. All the coatings were pre-cracked before deformation.The extent of the pre-cracking depends on the intensity and the sharpness of the basal planes texture of the coating and also on the misorientations across the grain boundaries. In the same way, zinc primary dendrites and recrystallised grains can hinder the crack propagation, limiting their extent.We can establish a correlation between the texture, the microstructure of the coatings (using a concept that corresponds to the mean free path of the crack) and the formability. As we know the process parameters, it is now conceivable that the texture of the coatings could be controlled.