Résumé:
The studies have been carried out on evaluating the quality of the produced
galvanization, in terms of the importance of the relevant phases present and how can be
controlled to achieve the desirable properties and therefore, making a better understanding
of the coating. This coating is done by hot dipping galvanizing process .This galvanneal was
conducted on the as received sheet which was produced from the steel plant with the
chemical composition of the low carbon steel : 0.08%C , 0.3%Si ,0.3%Mn , 0.04%P ,0.4%Al .
The temperature of the zinc bath was at 460 °C and Zinc purity 99.98%. An extra Aluminum
slabs are added to the bath to break up the spanges which are produced on the substrate as
result of the galvanization process. These specimens were galvanneal in the range
200,500,530, 650, and 800 °C for different time exposures 0.05, 0.5, 1, and 2 hours. There is
a lot of controversy regarding the designation and the mechanisms in the recent lieturature.
There are some systems to identify the phases and subdivide them on the chemical formula,
the most used terminology are pure zinc, and the three separate inter-metallic phases. The
specimens were inspected using the x.ray gonimeter at 35Kv, with the data provided in the
diffraction files for the crystal lattice spacing .The specimens were inspected using the
Mossbauer spectroscopy which makes use of the counts of the emitted radiation of Fe
atoms or the magnetic phases present which exhibit the Mossbauer effect. The results for
the x.ray have shown that, the ƴ Gamma existence was over temperature range between
500°Cand disappeared as the temperature approached 800°C. This is in support of the
pervious constructed binary diagram .The free zinc layer was seemed to be present, as was
appeared in the diffraction data and has the lowest area fraction at 350C for 0.5 hour
galvanneal and minimum fraction at 475 C for 1 hour galvanneal process. The most stable
phases occurred were as follows, with their d=nearest approach spacing and temperature of
occurrence for each phase, FeAl2O3/d=2.02A°/530°C, Fe2SiO4/d=1.45A°/800°C,
FeAl2/d=1.43A°/200 °C, (Fe2,Zn)Al2O4 /d=1.43A°/530°C, and Al13Fe4/d=2.05A°/800°C, and
hence the Fe-Aluminum phases were occurring in more proportion than any of the other
existing phases. The argument can be examined further, by studying the effects of the most
vital parameters prevailing over the process like chemical composition, degree of zinc purity,
zinc bath temperature and other interacting variables. Another feature worth mentioning
was the ZnFe phases were absent and might need some extra diffraction studies .Following
this diffraction study, the Mossbauer was carried out to determine the parameters of the
inter-metallic phase and their specific features, which in turn improves the understanding of
their behavior at the specified temperatures. The results for the Mossbauer effect have
shown elongated sixth of the α-Fe exceeding the common ration of 3:2:1, the sixth becomes
more elongated to become 4.5:3:1.5 and the hyperfine magnetic field gets smaller and the
sixth would appear squeezed
