Effect of Grain Structure on the Magnetic Properties of Alnico 8 Alloys

Abstract

In recent years, AlNiCo has regained attention by the advantages of low price, good high temperature performance and strong corrosion resistance. However, the lower magnetic properties of AlNiCo limit the wide range of applications. Directional solidification is a key process that affects the grain structure of magnets,and cylinders taken from the top, middle and bottom of the castings were analyzed by EBSD and TEM: the results showed that the grain orientation and size varied considerably throughout the height of the castings. The top part of magnet has the best grain orientation and the largest average grain size, leading to the highest remanence. The grain sizes decrease gradually from top to bottom, and the proportion of transverse grain boundaries increases, resulting in a small aspect ratio of the α1 phase and low coercivity. Therefore, the magnetic properties of the top are the best, the bottom has the worst magnetic properties and the middle is in between. AlNiCo columnar crystals with high orientation and large contribute to high performance, which provides a new idea to improve magnetic properties by regulating the grain structure.

Keywords: AlNiCo alloy Grain orientation Grain boundary Magnetic properties