A unique combination of in-situ and multi-scale methodologies to analyze damage mechanisms of temper rolled zinc coating

Coated sheets for car body are assembled by spot-welding and, more and more, by adhesive bonding. Thus, during life time, the coating endures stresses which can lead to the failure of the whole bonded assembly. The behavior of the zinc coating has then to be primarily studied during tension of flat samples. Several investigation techniques, including in-situ characterizations and 3D observations, are combined to observe and understand the damage mechanisms of the zinc coating during plastic deformation. A specific attention is paid to the influence of temper rolling which is usually applied on low-carbon steel sheets after annealing and hot-dip coating. Damage is mainly observed at the boundary of large zinc grains lying on the surface plateaus, non-deformed by rolling, and often nucleates at the defects due to dendritic zinc solidification.