Effects of Ta Addition and the Isothermal Magnetic Annealing Time on Magnetic Properties of AlNiCo Alloy

To meet the demand for high-performance rare-earth-free permanent magnet, the Ta-added AlNiCo permanent alloy has been prepared in this study. Effects of the Ta addition and isothermal magnetic annealing time on structure, micro-morphology, and magnetic properties of AlNiCo alloy have been investigated. An appropriate amount of Ta addition improves the permanent magnetic performance of the AlNiCo alloy. The optimal content of Ta addition is 0.6 wt%. It is found that with increasing isothermal magnetic annealing time, (BH)_max, H_cj, and B_r increase first and then decrease. The sample with the isothermal magnetic annealing time of 20 min shows the optimal permanent magnetic performance with (BH)_max, H_cj, and B_r of 5.73 MGOe, 1.85 kOe, and 9.16 kGs, respectively. Ta element aggregates at the joints between adjacent α₁ phases and plays the role of separator, which reduces the magnetic interaction between adjacent α₁ phases and improves permanent magnetic performance. A modest isothermal magnetic annealing time promotes the aggregation of Ta element at the joints between adjacent α₁ phases and suppresses the formation of small α₁ phases. This is the reason for the enhancement of permanent magnetic performance.