Solidification microstructure-dependent hydrogen generation behavior of AleSn and AleFe alloys in alkaline medium.

Abstract

This work deals with the development of quantitative correlations of hydrogen evolution performance with solidification microstructural and thermal parameters in Ale1Sn, Al e2Sn, Ale1Fe, and Al-1.5Fe [wt.%] alloys. The cellular growth as a function of growth and cooling rates is evaluated using power type experimental laws, which allow determining representative intervals of microstructure length scale for comparison purposes with the results of immersion tests in 5 wt%NaOH solution. For both Al alloys systems, hydrogen evolution becomes slower as the alloy solute content increased. However, for a given alloy composition, whereas a more homogeneous distribution of Sn-rich particles promotes faster hydrogen generation using AleSn alloys, coarsening of Al6Fe IMCs (intermetallic compounds) fibers favors hydrogen production using AleFe alloys. When solidification conditions that result in a range of cellular spacings within 16 and 19 mm are considered, the specific hydrogen production of the Al-1wt.%Fe alloy is higher than that of the other studied alloys.