Quantification of hydrogen trapping in multiphase steels:Part II – Effect of austenite morphology

Turk, A. and Pu, S.D. and Bombač, D. and Rivera-Díaz-del-Castillo, P.E.J. and Galindo-Nava, E.I. (2020) Quantification of hydrogen trapping in multiphase steels:Part II – Effect of austenite morphology. Acta Materialia, 197. pp. 253-268. ISSN 1359-6454

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Abstract

We tackle the role of austenite in multiphase steels on hydrogen diffusion systematically for the first time, considering a range of factors such as morphology, interface kinetics and the additional effect of point traps using both experiments and modelling. This follows the findings from part I where we showed that austenite cannot be parametrised and modelled as point traps under the assumption of local equilibrium, unlike grain boundaries and dislocations. To solve this, we introduce a 2D hydrogen diffusion model accounting for the difference in diffusivities and solubilities between the phases. We first revisit the as-quenched martensite permeation results from part I and show that the extremely low H diffusivity there can be partly explained with the new description of austenite but is partly likely due to quench vacancies. We then also look at the H absorption and desorption rates in a duplex steel as a case study using a combination of simulations and experiments. The rates are shown to depend heavily on austenite morphology and the kinetics of H transition from ferrite to austenite and that an energy barrier is likely associated to this transition. We show that H diffusion through the ferrite matrix and austenite islands proceeds at similar rates and the assumption of negligible concentration gradients in ferrite occasionally applied in the literature is a poor approximation. This approach is also applicable to other austenite-containing steels as well as other multiphase alloys.

Item Type:
Journal Article
Journal or Publication Title:
Acta Materialia
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2500/2504
Subjects:
ID Code:
146526
Deposited By:
Deposited On:
26 Aug 2020 09:50
Refereed?:
Yes
Published?:
Published
Last Modified:
22 Sep 2020 05:10