On the Properties of Semihard Magnetic Alloys “Recalloy” in the Fe-Nb-Co-W and Fe-Ta-Co-W Systems

Abstract

The magnetic properties, the thermal expansion coefficient α, the electrical resistivity ρ and the hardness H_v have been studied for the Fe-<about 3 mass%Nb-20 mass%Co-<10 mass%W alloys and Fe-<about 5 mass%Ta-20 mass%Co-<10 mass%W alloys. All the alloys used in this study were water quenched from 1323 K, cold drawn by 97.2% reduction in area and subsequently reheated at 673-1273 K for the period less than 18 ks. The magnetic properties of the Fe-Nb-Co-W and Fe-Ta-Co-W alloys depend remarkably on the tungsten content, the reheating temperature and the reheating time. Among these properties, both B_r⁄B_s and H_c increase particularly with increasing W content. The thermal expansion coefficient α shows a minimum at the composition of 3 mass%W in the former alloys and a maximum at 7 mass%W in the latter alloys, respectively, and these values are less than 10×10⁻⁶ K⁻¹. With increasing W content in both of these alloy systems, ρ and H_v increase monotonically for the most part. When water quenched, cold drawn and subsequently reheated at 973 K for 18 ks, an Fe-about 2 mass%Nb-20 mass%Co-5 mass%W alloy exhibits the following values: B₈=1.97T at 8 kA·m⁻¹, B_r=1.85T, B_r⁄B₈=0.94, H_c=1.84 kA·m⁻¹, \sqrt(BH)_max⁄B_rH_c=0.94, α=9.8×10⁻⁶ K⁻¹ at 273–313 K, ρ=0.263 μΩ·m and H_v=404. Also, an Fe-about 3 mass%Ta-20 mass%Co-5 mass%W alloy exhibits: B₈=2.02T, B_r=1.89T, B_r⁄B₈=0.94, H_c=2.03 kA·m⁻¹, \sqrt(BH)_max⁄B_rH_c=0.94, α=9.3×10⁻⁶ K⁻¹, ρ=0.234 μΩ·m and H_v=446.