Grain Growth and Texture Formation by Annealing of Rapidly Quenched High Silicon-Iron Alloy

Abstract

It is well known that soft magnetic properties such as the coercive force and the permeability of 6.5 mass% silicon-iron ribbons prepared by a rapidly quenched roll method can be improved by annealing at 1373 K in a vacuum atmosphere. This paper reports results on the grain growth during annealing and texture formation in the 6.5 mass% silicon-iron ribbons. In the as-prepared ribbon, non-oriented columnar grains about 10 μm in diameter were observed, which grew from the surface to the inner part of the ribbon. When the annealing temperature was around 973 K, the primary recrystallization was observed near the middle part of the ribbon thickness, and the grain size increased with increasing annealing temperature. At the annealing temperature of 1223 K, the grain size became 30∼40 μm. Around the annealing temperature, the motive force of the grain growth is the grain boundary energy. Above 1223 K, however, the surface energy plays an important role in the grain growth. When the ribbons were annealed at 1373 K, grains with {100} surface preferentially grew, so that the ribbon surfaces are covered with these grains after annealing for 3.6 ks (1 h). When the annealing temperature was kept above 1473 K, grains with {110} surface grew preferentially, and all the ribbon surfaces became parallel to {110} plane.