In Situ Observation of Inclusions Pinning Effect of Austenite Grain Growth in Fe−80Ni Permalloy With or Without Ce treatment

Abstract

The magnetic properties of Fe−80Ni alloy are significantly influenced by its microstructure, making it the focus of research. In this study, we investigated the pinning effect of inclusions on austenite grain growth in Fe−80Ni using high-temperature confocal laser scanning microscopy (HT-CLSM) and explored the impact of Ce treatment on the pinning process and magnetic properties of Fe−80Ni alloy. The findings revealed that primary inclusions were transformed into Ce-containing inclusions with Ce treatment. Moreover, the Ce treatment resulted in a certain reduction in the number of inclusions. Simultaneously, there was an enhancement in the level of inclusions after deformation and annealing with Ce treatment. The HT-CLSM results highlighted that these inclusions impede grain boundary migration, facilitating the formation of finer grains due to the pinning effect during the annealing process. Furthermore, a reduced number of inclusions led to a larger average grain size after annealing, from 152.3 μm to 170.2 μm, consequently improving the magnetic properties of the alloy by 10-20%. To assess the deformability of different inclusions, we calculated the Young's modulus, yielding values of 141.5 GPa for CeO₂ and 82.4 GPa for 6SiO₂·Al₂O₃, respectively. Additionally, we elucidated the evolution of inclusion pinning during annealing based on TEM results.