Effect of Σ3 grain boundaries on microstructure and properties of oriented Fe-6.5 wt%Si in twin-roll strip casting

•A large number of Σ3 grain boundaries characterized with twin were found in the solidification structure of strip-cast Fe-6.5 %Si alloy, especially the ratio over 15% in the solidified shell.•Σ3 grain boundaries was inherited into recrystallization structure during warm-rolling and heat treatment process, which could improve the plastic workability of oriented Fe-6.5 wt%Si.•Completely abnormal grain growth with accurate Goss orientation was obtained, resulting in magnetic induction intensity B8 of 1.76 T and iron loss of P10/50 = 0.59 W/kg. Oriented Fe-6.5 wt%Si alloy with excellent magnetic properties was prepared by twin-roll strip casting (TRSC). We studied the abnormal Σ3 grain boundaries in the as-cast strip. The experimental results demonstrated that the Σ3 grain boundary (GB) in oriented Fe-6.5 wt%Si steel had a good thermal stability, which could refine the microstructure by inhibiting growth of structure in as-cast strip. Moreover, the Σ3 GB in Fe-6.5 wt%Si as-cast strip could improve the toughness of matrix and restrain the propagation of cracks, which was beneficial to its plastic working. The Σ3 GB was relatively stable during warm rolling and could be inherited partly after annealing. At the same time, the low migration rate of Σ3 GB in primary recrystallization structure could stabilize the matrix and help to obtain the abnormal growth of Goss grains. The finished Fe-6.5 wt%Si steel had excellent magnetic properties, B800 and P10/50 were 1.76 T and 0.59 W/kg, respectively.