A Predictive Model Accounting for the Mechanical Behavior of Galvanized Alloy Layers on the Mild Steel

Zinc coating is formed by the heterogeneous assembly of the ?, ?1, ?, ? and ? phases whose mechanicalproperties greatly differ from each other. thermal strains resulting from large differences betweenthermal expansion coefficients are partially relaxed by the formation of a crack network. in order tomodel this phenomenon, initial hardness, thermal expansion coefficient ?i and toughness (kic) of thephases were determined. hardness testing experiments performed on the galvanizes samples with andwithout annealing revealed that during the cooling down of the samples in the coating process, there wassome residual stress in the coating due to the difference between the thermal expansion coefficients ofthe phases. in this regard, maximum hardness, 340 hv, was obtained for ? phase and its toughness wasmeasured to be about 2mpa?m, thereby revealing that ? phase was completely brittle compared to otherphases. modeling the behavior of the phases present in the coating demonstrated that during the coolingstage, at first, some micro-cracks were formed in ? phase and grew in two stages: i) perpendicular to the?/? interface and ii) parallel to the ?/? interface. the results revealed that when the thickness of ? phasewas more than 5?m, there was a good agreement between the experimental results and the proposedmodel. also, due to the properties of the coating layers, the resulted stresses could not delaminate thecoating.