The influence of Mn content on the wettability of dual-phase high-strength steels by liquid Zn-0.23 % Al

The influence of Mn content on the wettability of dual phase high strength steels (1.8, 2.2, and 2.6 wt% Mn at a fixed Si content of 0.12 wt%) was investigated by a dispensed sessile drop method with liquid Zn-0.23 wt% Al at 450 °C (723 K). Before the wetting tests, the samples were annealed in a galvanizing simulator under 15 % H ₂-N ₂ atmosphere, and the surfaces were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, and a transmission electron microscope. It was found that the surface coverage of the oxides for the three samples at different Mn contents of 1.8, 2.2, and 2.6 wt% were estimated to be 0.55, 0.58, and 0.71, respectively, and surface oxide modification occurred from MnSiO ₃ to Mn ₂SiO ₄ to MnO as the Mn content increased. From the wetting experiments, the initial contact angle increased from 101 to 110°, which could be explained by classical wetting theory by means of the Cassie equation. On the other hand, the reactive wetting was affected by the sorts of surface oxides and the fraction. It was considered that the dissolved Al reduced MnO to increase the bare metallic Fe surface at the triple line, which enabled the continuing reactive wetting process.