An experimental investigation on B2 phase transfer and grain boundary character on mechanical properties of rapidly cool
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The combined effect of B2 phase transfer and grain boundary character on mechanical properties of the Fe–6.5 wt% Si alloy was investigated. The microstructures and textures of the Fe–6.5 wt% Si alloy under four cooling modes were characterized by X-ray diffraction, transmission electron microscope, and electron backscattered diffraction. The results reveal that the maximum nano-hardness value (8.9 GPa) results from the two-step air-cooling sample, while for the two-step water-cooling sample, the minimum value (5.3 GPa) is achieved. The transformation of the B2 phase affected by the water-cooling process is a critical factor in obtaining the lower APB energy and eliminating the brittlenes. A large fraction of the coincidence site lattice boundaries that formed on the sheet experienced the two-step water-cooling process due to a uniform and sharp c-fiber recrystallization texture comprising the {111} h110i and {111} h112i components, which enhances resistance to intercrystalline effect and improves mechanical properties in comparison with the two-step air-cooling process.
I. INTRODUCTION
As a kind of soft magnetic material, the Fe–6.5 wt% Si alloy presents a contribution combining low iron loss with high magnetic induction, widely used as the choke coil, high-frequency transformer, as well as the highfrequency motor.1 Owing to the two ordered structures (B2 and DO3) with high brittleness, it is almost impossible that Fe–6.5 wt% Si sheets are manufactured using the conventional cold rolling process2; then attention has been accorded to the impact of B2 and DO3 ordered structures on mechanical characterization.3,4 According to the difference in the nucleation rate of B2 and DO3 ordered phases,5 the transformation of the B2 phase may be affected by means of the cooling process. As a result, it is reasonable to believe that controlling B2 (FeSi) ! DO3 (Fe3Si) in the cooling process will be an effective way to reduce the order degree and exert an influence on mechanical characterization of the Fe–6.5 wt% Si alloy.6 Presently, grain boundary engineering has become a widely applied concept based on the idea of controlling the frequency of coincidence site lattice (CSL) grain boundaries,7 and the research work on mechanical propertiesis of the Fe–6.5 wt% Si alloy is focused on the effect of grain boundary character strongly influenced by the texture evolution.8 Watanabe et al.9 investigated
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.433
that the fraction of 50–75% of percolation-resistant low-RCSL boundaries was required to interrupt the network of degradation susceptible random boundaries, controlling intergranular brittleness and improvement in ductility of the high-performance Fe–6.5 wt% Si alloy. Zhang et al.10 pointed out that controlling the grain boundary character distribution (GBCD) in the Fe–6.5 wt% Si alloy could be utilized as a novel and effective method, and the optimum GBCD was also beneficial for the control of impurity-elem
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