Effect of P addition on nanocrystallization and high temperature magnetic properties of low B and Nb containing FeCo nanocomposites

摘要

The P content dependencies of the nanocrystallization behaviors and high temperature magnetic properties of the Fe_(54.6)Co_(29.4)Si_(2.8)(B_(0.8-Y)P_Y)_(14)Nb_1Cu_1 (Y = 0, 0.2, and 0.3) alloys have been investigated. Alloys were prepared by melt spinning and subsequently annealed in an argon atmosphere to induce nanocrystallization. P addition increases primary crystallization temperature (T_(X_1)), thermal stability (ΔTx), and activation energy (Q_(JMA)) for secondary crystallization in as-cast alloys. The saturation induction (B_s) of 1.68 T for as-cast P free alloy decreases continuously with the addition of P. However, the soft magnetic properties are enhanced for P added alloys. The XRD pattern reveals that grain refinement increases with increasing P contents. Alloys annealed at 430 ℃ confirm primary nanocrystallization of α-FeCo in the amorphous matrix, while annealing at 550 ℃ causes secondary crystallization of other non-magnetic phases as well. The magnetic moment of as-cast and annealed alloys, measured by vibrating sample magnetometry (VSM), has minimum values at two temperatures, labeled Tc_1, Tc_2, prior to secondary crystallization, corresponding to the ferromagnetic transitions of as-quenched amorphous and residual amorphous phase, respectively. The stabilization of amorphous phase delays primary crystallization, resulting in increase of Tc_1 for P-rich as-cast alloys.