THE EFFECT OF INGOT HEAT-TREATMENT ON THE MAGNETIC-PROPERTIES OF PR-FE-B-CU HYDROGEN DECREPITATION SINTERED MAGNETS

The as-cast ingot microstructure of the alloy Pr20.5Fe73.8B3.7Cu2 has been modified by a homogenization heat treatment of 1000-degrees-C for 24 h. For particular processing conditions, sintered magnets prepared from the homogenized alloy using the hydrogen decrepitation (HD) process exhibit superior remanence and energy product to those prepared from the as-cast ingot. The squareness factor has also been improved considerably in the magnets prepared from the homogenized alloys. This work also showed that the influence of the initial microstructure on the intrinsic coercivity of Pr-Fe-B-Cu HD sintered permanent magnets diminishes rapidly with increasing milling time and is a minimum when the coercivity reaches the maximum value of about 20 kOe.