METASTABLE A1 PHASE IN AL-DOPED ND-FE-B MAGNETS

The role of the metastable Al phase in the coercivity of Al-doped Nd-F e-B magnets has been investigated in a magnet enriched in both Nd and Al. The as-sintered magnet (intrinsic coercive field H-1(c) = 3.6 kOe) contains an additional phase with Curie temperature T(c) = 180-degree s-C, while the annealed (600-degrees-C/1h) magnet (H-i(c) = 12.1 kOe) does not. As-cast ternary alloys with compositions Nd(20-x)at.%Fe-xat. %Al(x = 1-10) show the metastable A1 phase with reduced T(c), but anne aled alloys show the mu and delta phases of the Nd-Fe-Al system. Quate rnary Nd-Fe-B-Al alloys were also studied. The disappearance of the fe rromagnetic phase with T(c) = 180-degrees-C is associated with the dec omposition of A1. The magnetic properties of delta are discussed and t he transformation kinetics of A1 are studied.