Effect of Secondary Decomposition on Coercivity of Fe-Co-Cr Alloys With 15 Co

摘要

The microstructure and magnetic properties of Fe-Co-Cr alloys with 15 wt% Co were investigated using transmission electron microscopy and magnetic measurements. The secondary decomposition within both the α_2-phase matrix and the α1-phase particles was observed for magnets subjected thermo-magnetic treatment and subsequent stepped aging or continuous-cooling treatments. During high-temperature treatments (630-600°C), when the α_2 phase is dominant (the volume fraction is more than 50%), the secondary decomposition of this phase takes place (α_2 → α_1' + α_2'). The deterioration of magnetic insulation of α_1-phase particles results in the decrease in the coercive force of alloys. Below 600°C, when the α1 phase is dominant (the volume fraction is more than 50%), the splitting of elongated α_1-phase particles occurs. When the temperature of stepped-aging decreases in high steps, the secondary decomposition (α_1 → α_1' + α_2') leads to the splitting of initial α_1-phase particles into fine slightly elongated particles and the decrease in the coercive force.