Correlation between hydrogen absorption capacity and microstructure of Fe-rich Sm-Co-Fe-Cu-Zr permanent magnetic alloys

Abstract

The correlation between hydrogen absorption capacity (HAC) and the microstructure of Sm26.2CobalFexCu4.0Zr2.3 (x = 23 wt%, 25 wt%, 27 wt%, 30 wt%) ingots and cast strips was systematically investigated. As the temperature rises from 373 to 423 K, the activation time, hydrogen absorption time and HAC of the Sm26.2CobalFe23Cu4.0Zr2.3 ingot decrease by 14.4%, 14.1%, and 19.3%, respectively. Dispersed 1:5 phase provides more channels for hydrogen diffusion, which is the main reason that HAC increases with the x increasing. The HAC of the same compound strips increases as the particles size of the pre-crushed decreases. However, no further embrittlement behavior appears in pre-crushed strips, which reaches an equal HAC as ingots. Micro-computerized tomography reveals that ingots contain small spherical-like holes and large flake micro-cracks, whereas strips mainly contain elliptical pores. The effects of grain size and inner defects size on structure stability were invested by Abaqus. Simulation results reveal that the superior embrittlement behavior of the ingots is predominantly influenced by the presence of large flake-like micro-cracks.