Enhanced hydrogen adsorption capability of 2:17-type Sm-Co strips via microstructure modification

The hydrogenation kinetics of Sm26.2CobalFexCu4.0Zr2.3 (x = 23, 27 in wt%) strips (Fe23 and Fe27 strips) has been investigated. The phase composition, morphology, surface roughness and the inner pores of the strips also have been studied by XRD, SEM, optical profilometer and non-destructive micro-computerized tomography. Compared to Fe23 and Fe27 strips, heat-treated strips (H-Fe23 and H-Fe27) and corrosion heat-treated strips (HC-Fe23 and HC-Fe27) exhibit a relatively higher hydrogen absorption capability. Fragmentation behavior occurs in HC-Fe23, H-Fe27 and HC-Fe27 strips during hydrogenation. After heat treatment, the grain size and inner pore size increase, leading to the disappearance of fine crystal strengthening and the concentration internal stress. For corrosion-treated strips, increased surface roughness and deeper grooves result in the formation of surface stress concentration, ultimately leading to an increased susceptibility to hydrogen embrittlement. Accordingly, the increase of grain size, inner pore size and rougher surface is beneficial for hydrogenation and hydrogen embrittlement.