The effect of microstructure on the hydrogen ductilisation process (HyDP) for NdFeB alloys

Previously, the authors have shown that it is possible to make the normally brittle NdFeB alloys ductile at room temperature utilising the high temperature solid Hydrogenation-Disproportionation (s-HD) reaction, which produces a mixture of α-Fe, NdH2 and Fe2B. This mixture can be deformed at room temperature and recombined, under vacuum at elevated temperatures, to form a submicron Nd2Fe14B grain structure, with a degree of anisotropy relative to the load applied, and this has been termed the “Hydrogen Ductilisation Process HyDP”.

However, in previous works was the degree of ductility was limited by presence of the minority NdFe4B4 phase, and the redistribution of Nd-rich phase during recombination caused cavitation in the final microstructure, reducing the density.

The work presented here investigates the variations in mechanical behaviour in the ductile condition for various different disproportionated microstructures. The investigation showed that there was a significant difference in the ductile behaviour between coarse and finely disproportionated microstructures.