Abstract
The influence of cold rolled topography on titanium (Ti) and titanium niobium (TiNb) interstitial free steels has been investigated with respect to FeZn intermetallic phase development and the adhesion properties of hot dip galvanised and galvannealed coatings. It is shown that substrate chemistry determined the initial reactivity in the galvanising bath and the consequent development of FeZn intermetallic phases. TiNb steels were found to have a lower susceptibility to coating failure, in particular flaking, during forming operations. The results suggest that this is due to the higher interfacial strength of TiNb material, which in part is determined by the nucleation of orientated FeZn crystals with slow growth rates on {111} αFe grains. this reduces the effective surface area of the brittle Γphase and increases the microroughness of the galvanneal coating and the substrate/coating interface. An interaction between FeZn phase growth and topographical features was found. However, the consequent effect on coating performance remains unclear and is the subject of further research.
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