Preparation and magnetic hardening of low Ti content (Sm,Zr)(Fe,Co,Ti)12 magnets by rapid solidification non-equilibrium method

Abstract

The Sm–Zr–Fe–Co–Ti quinary-alloys with ThMn₁₂ structure has attracted wide attention for ultra-high intrinsic magnetic properties, showing potentiality to be developed into rare-earth permanent magnets. The Ti element in alloys is crucial for phase stability and magnetic properties, and lower Ti content can increase intrinsic magnetic properties but reduce phase stability. In this study, the 1:12 single-phase melt-spun ribbons with low Ti content was successfully prepared using a rapid solidification non-equilibrium method for the Sm_1.1Zr_0.2Fe_9.2Co_2.3Ti_0.5 quinary-alloy. However, this non-equilibrium ribbon did not achieve good magnetic hardening due to the uneven microstructure and microstrain. Then, annealing was carried out to eliminate micro-strain and homogenize microstructure, therefore, remanence and coercivity were significantly improved even the precipitation of a small amount of α-Fe phase which were not conducive to coercivity. The remanence of 86.1 emu/g and coercivity of 151 kA/m was achieved when annealing at 850 °C for 45 min. After hot pressing, under the action of high temperature and pressure, a small portion of ThMn₁₂ phases in the magnet decompose into Sm-rich phases and α-Fe, while remanence of 4.02 kGs (1 Gs = 10⁻⁴ T), and coercivity of 1.12 kOe (1 Oe = 79.5775 A⋅m⁻¹) were still acquired. Our findings can provide reference for exploring practical permanent magnets made of 1:12 type quinary-alloys.