Some kinetic and microstructural aspects during hydrogen-induced phase transformations in [formula omitted] alloys

Abstract

There are discussed some experimental data on the kinetics and microstructure of direct and reverse hydrogen-induced diffusive phase (HIDP) transformations in the Nd 2 Fe 14 B type alloys ( Nd 34.0 Fe 64.8 B 1.2 (wt.%) industrial alloy and original Nd 2 Fe 14 B alloy ( Nd 15.0 Fe 77.0 B 8.0 (at.%)). It has been established that a hydrogen-vacuum treatment carried out in accordance with the isothermal kinetic diagrams for HIDP-transformations in these alloys leads to a homogeneous microstructure and allows to avoid abnormal growth processes a main hard magnetic Nd 2 Fe 14 B phase. It is shown that the kinetic factor is one of the main factors determining microstructure features of Nd 2 Fe 14 B type hard magnetic alloys. On the base obtained results, new modified HDDR-treatment scheme based on isothermal kinetic diagrams of HIDP-transformations in Nd 2 Fe 14 B type alloys has been proposed.