Microstructure and soft magnetic properties of nanocrystalline Fe–Si–B–Cu–Nb soft magnetic alloy by laser annealing

The impact of laser annealing on the nanocrystalline Fe–Si–B–Cu–Nb soft magnetic alloy has been investigated. The experimental results showed that the microstructure of nanocrystals produced by laser annealing is comparable to that of furnace annealing. However, the annealing time plays a crucial role in determining the grain size and crystalline fraction evolution, thereby affecting both the coercivity and saturation magnetization. Nonetheless, the volume crystalline fraction of the laser annealed samples is lower than that of the furnace annealed ones due to the ultrahigh heating and cooling rate, which hinders the growth of nanocrystals and crystallization region. In addition, laser annealed samples demonstrate no distinct crystallization at high scanning speeds, even with noticeable changes in soft magnetic properties. Furthermore, the correlation between coercivity and grain size is examined, revealing a progressive decline in coercivity with a decrease in grain size. It is also found that the rule Hc ∝ D6 is also valid in laser annealing for relatively larger grains, whereas the rule becomes Hc ∝ D3 for smaller grains.