Orientation relationship between Γ phase and α–Fe in commercial galvanneal steel coating

Abstract

The steel coatings' forming technology and their resulting mechanical performance are of primary concern to the automobile and appliance industries, for they determine directly the long-term structural integrity of the final products. In automobile industry, steel coating plays a crucial role for extended warranty of their product. The recent trend in coatings is an increase in galvannealed coatings.The iron-zinc compound coatings produced by galvannealing bring about a dramatic improvement, in terms of coating performance, compared to pure zinc coatings. The improvement includes corrosion resistance, weldability and paintability in addition to energy and material efficiency. However, there is still one serious obstacle which prevents the industry-wide use of galvannealing as the dominant steel coating technology: Its powdering and flaking tendency during press forming processes. There are a number of empirical hypotheses which propose that the presence of various Fe-Zn intermetallic phases influences the powdering/flaking tendency of galvannealed coatings. Nevertheless, not enough microstructural information is available except those obtained by SEM and X-ray diffraction.