METASTABLE AND STABLE MAGNETIC PHASES IN AS-CAST AND ANNEALED PR80FE15(B1-XCX)(5) ALLOYS LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-1.0)

In as-cast Pr80Fe15(B1-xCx)(5), samples metastable A(1) (T-c=225 degre es C) was the predominant magnetic phase in the whole composition rang e, with intrinsic properties that were not affected with increasing C content. Up to x=0.75 this phase coexist with an additional minor magn etic phase having T-c=263 degrees C which has been labelled by us to a s A(3). Upon annealing at 600 degrees C A(1) dissolves and the followi ng stable phases were observed: a) Pr2Fe14B and A(3) for 0.0 less than or equal to x less than or equal to 0.75, and; b) an unknown stable p hase D-1 with coercivity around 2.1 kOe and Curie temperature of 230 d egrees C for x=1.0 D-1 is the predominant phase for annealing times le ss than 8 h while for 8 and 16 h annealing an additional phase with T- c = 17 degrees C appears. The latter has been tentatively identified a s Pr2Fe17. SEM and X-ray microanalysis studies were performed on Pr80F e15C5 samples in the as-cast state and after 16 h of annealing. The as -cast sample shows large Pr-rich grains immersed in a fine eutictic mi crostructure consisting of Pr and Fe. In annealed samples. both large square or polygonal grains and a needle-like phase are formed. The lat ter is believed to be D-1. (C) 1998 Elsevier Science S.A.