Phase evolution and magnetic properties of PrxFe82−x−yTiyCo10B4C4 (x = 9–10.5; y = 0, 2) nanocomposites

The phase evolution and magnetic properties of PrxFe82−x−yTiyCo10B4C4 (x = 9–10.5; y = 0, 2) melt-spun ribbons have been investigated. The effects of wheel speed and annealing on the crystallization and magnetic properties of the ribbons are discussed in detail. It was found that Ti substitution enhances the glass forming ability of the Pr2(Fe, Co)14(C, B)-type ribbons. For a high wheel speed Vs (18 m/s), the Ti-substitution ribbons consist of a significant fraction of amorphous phase, and show typical two-step magnetic behavior, while most of the Ti-free ribbons are mainly composed of the crystalline 2:14:1, α-(Fe, Co) and 2:17 phases. With decreasing wheel speed, all ribbons are fully crystallized, and a larger fraction of the magnetically hard 2:14:1 phase is formed. The content of metastable 2:17 phase in the ribbons decreases with increasing Pr and Ti substitution. A Br of 9.5 kG, iHc of 9.8 kOe, and (BH)max of 16.0 MGOe were obtained in the as-spun Ti-substituted Pr10.5Fe69.5Ti2Co10B4C4 ribbon prepared at Vs = 15 m/s. For all the as-spun, Ti-free ribbons prepared at various Vs, the (BH)max is lower than 10 MGOe owing to a poor shape of the demagnetization curve. Ti substitution also helps suppress the grain growth of 2:17 phase during the annealing process, and simultaneously promotes the growth of magnetically hard 2:14:1 phase. The annealing treatment significantly improves the magnetic properties of the Ti-substituted ribbons with higher Pr contents. No obvious improvement of magnetic properties was found in the Ti-free ribbons after annealing.