Influence of microstructure and crystallographic texture on hydrogen diffusion in IF-steel

The relation between microstructure, crystallographic texture and hydrogen diffusion has been studied in an IF-steel. The steel samples were deep drawn until 10%, 20%, 30% and 40% strain levels and then hydrogen diffusion coefficients were determined using Helios II system. Light optical microscope (LOM), scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) were used for microstructural characterization and crystallographic texture studies. The dependence of microstructural parameters was evaluated by Pearson correlation coefficient (PCC) values. Those evaluations showed that local misorientations, crystallographic texture and dislocation density depend on each other. The PCC values show that grain size and dislocation density are the independent microstructure related parameters and those parameters were used to build a model to predict hydrogen diffusion coefficient by multiple linear regression analysis. Using this model sensitivity analysis was also performed to understand which parameter the hydrogen diffusion is most sensitive to. The results of this analysis show that hydrogen diffusion is more sensitive to dislocation density, which indicates that dislocations are more effective trapping sites for hydrogen atoms. On the other hand, grain boundaries are less effective trapping sites since they also provide an additional diffusion mechanism.