Magnetic properties evolution and crystallization behaviour of vacuum- and air-long-term-annealed rapidly quenched Fe80.3Co5Cu0.7B14 alloy

Abstract

This work aims to investigate the isothermal crystallization behaviour, crystal structure and magnetic properties evolution of long-term (up to 300h) low temperature (210 and 260°C) vacuum- and air-annealed Fe80.3Co5Cu0.7B14alloy. Before the α-Fe(Co) phase crystallization, the primary relaxation process has been identified at a temperature range up to 340°C. The relaxation process performed under 210°C for 300h did not initiate the crystallization process. However, the topological and compositional short-range rearrangements improved magnetic properties remarkably. Annealing 150h at 260°C helps to deliver enough energy to stabilize the glassy state and initiate the crystallization process fully. Structural and magnetic properties evolution of 150h annealing at 260°C corresponds to the evolution presented during isochronal 20min annealing at 310°C. Magnetic properties Bs = 1.75-1.79T, Hc < 20 A/m and P10/50are similar to those for 20min of annealing at 310°C. Comparison of core power losses from up to 400kHz frequency dependences of long-term low temperature annealed alloy with 20min classical annealing at 310°C shown that presented here long-term annealing is energetically insufficient to bring the glassy state system into the same low level of core power losses efficiency.