Influence of microstructure and texture on the formability character of industrially produced galvannealed coatings on three interstitial free steels

The formability character of industrially produced galvannealed coatings on three interstitial free steels has been investigated by carefully characterizing the substrate as well as coating microstructure and texture. The steel IF1 shows the highest amount of the beneficial δ phase in the galvannealed coating, while the IF2 shows the least and IF3 an intermediate amount of the δ phase. Correspondingly, the coating Fe content is minimum for the IF1 and maximum for IF2, with the IF3 displaying an intermediate amount. In the IF1 sample almost a complete fiber of the type {01.3}<uv.w> is present, the fiber character changes into a set of discrete orientations in the IF2 and the IF3 samples. A high amount of delta phase and a low iron content in the coating, along with a non-basal and uniform {01.3}<uv.w> coating texture have been found to be beneficial, leading to a lower powdering resistance of the coating. On the other hand, the density of the {111}–{113}–{313}–{001}–{101} planes of substrate steels appears to control the growth of the zeta phase in the coating.