Effect of annealing atmosphere on microstructure and magnetic properties of high Si-Fe alloys

Structure and magnetic properties of rapidly solidified 6.5 mass%Si-Fe alloy ribbons were studied by controlling the atmosphere during heat treatment. The ribbons were annealed in three kinds of atmosphere listed as below. (1) in the vacuum atmosphere for 3.6 ks at 1448 K (2) in the sulfur atmosphere for 3.6 ks at 1448 K (3) in the vacuum atmosphere for 180 s at 1373 K and the sulfur atmosphere for 3.6 ks at 1448 K. The structure of ribbon, which were showed random structure at as prepared state, was developed into (110) texture by the heat treatment (1). On the contrary, the structure was developed into (100) texture by the heat treatment (2). In the case of the heat treatment (3), the structure of ribbon was also developed into (100) texture and the grain size was large such as 2.5-5 mm, as compared with heat treatment (1) and (2). The coercive force decreased to 2-4 A/m remarkably.