Abstract：Thin strip casting through water-cooled copper rolls is used to directly prepare liquid alloys into 1.5-3.0 mm thin strips. This process exhibits notable characteristics of sub-rapid solidification and near-final forming, which enhances the solidification undercooling and temperature gradient at the solid-liquid interface, significantly affecting the alloy's microstructure, texture, and secondary phase evolution. Thus, this technique holds tremendous potential in the preparation of special alloys. Fe-Si, Fe-Ga, and Fe-Cr alloy strips were obtained in this research through strip casting processes. The microstructure, proportions, and distribution of low-energy grain boundaries in the solidification structure were observed using techniques such as metallography, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Additionally, a model experiment was designed to verify the formation mechanism of low-energy grain boundaries. The results showed that under large undercooling conditions, Fe-Si/Cr alloys formed special grain boundaries such as Σ1/Σ3/Σ5/Σ9 through grain/nuclei interface selection. The energy level of grain boundaries was closely related to the degree of undercooling; higher undercooling led to the formation of high Σ value grain boundaries like Σ5/Σ9, while at elevated temperatures, the lowest-energy Σ1 grain boundaries became more stable. This phenomenon of grain boundary interface selection was replicated and confirmed using monotectic alloys. Low-energy grain boundaries exhibited a lower migration rate, stabilizing the size of the matrix grains and inducing abnormal grain growth. Consequently, the Fe-1.5%Si strip obtained through industrial processing achieved abnormal {100} oriented grain growth, and during the rolling-annealing process, Cube texture was significantly strengthened, resulting in a high magnetic induction value in both the transverse and longitudinal directions. Furthermore, the in-depth investigation and physical metallurgy explanation of the formation mechanism of special grain boundaries in the sub-rapid solidification process can be applied in thin strip casting, laser additive manufacturing, powder forming, and other special metallurgical processes, thereby promoting advancements in these technologies.
袁国, 张元祥, 王洋, 方烽, 李振垒, 王国栋. 薄带铸轧凝固组织的低能晶界及遗传效应[J]. 钢铁, 2023, 58(9): 157-166.
YUAN Guo, ZHANG Yuanxiang, WANG Yang, FANG Feng, LI Zhenlei, WANG Guodong. Low-energy grain boundaries and their hereditary effects on microstructures in strip casting[J]. Iron and Steel, 2023, 58(9): 157-166.
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2023, Vol. 58 
