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

Abstract

Magnetic properties, thermal expansion coefficient α, electrical resistivity ρ and hardness H_v have been studied for the Fe-<about 3%Nb-20%Co-<7%Mo alloys and Fe-<about 7%Ta-20%CO-<7%Mo alloys. All alloys used in this study were water quenched from 1050°C, cold drawn by 97.2% reduction in area and subsequently reheated at 400∼1000°C for less than 5 h. The magnetic properties of Fe-Nb-Co-Mo and Fe-Ta-Co-Mo alloys depend remarkably on the molybdenum concentration, reheating temperature and reheating time. Among these properties, both B_r⁄B_s and H_c increase particularly with increasing Mo content. α shows a minimum at the composition of 3.5%Mo in the former alloys and a constant value at the composition range of 1∼4%Mo in the latter alloys, respectively. With increasing Mo 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 700°C for 30 min, an Fe-about 2%Nb-20%Co-3%Mo alloy exhibits the following values: B₈=2.01 T at 8 kA·m⁻¹, B_r=1.91 T, B_r⁄B₈=0.950, H_c=2.08 kA·m⁻¹, \sqrt(BH)_max⁄B_rH_c=0.910, α=9.5×10⁻⁶ at 0∼40°C, ρ=0.274 μΩ·m and H_v=394. Also, an Fe-about 3%Ta-20%Co-3%Mo alloy exhibits: B₈=2.05 T, B_r=1.95 T, B_r⁄B₈=0.951, H_c=2.13 kA·m⁻¹, \sqrt(BH)_max⁄B_rH_c=0.931, α=10.1×10⁻⁶, ρ=0.234 μΩ·m and H_v=429.