한국주조공학회

The effects of B additions, alone or in combination with Si, on the microstructure, DO_3⇌B2 transition temperature(T_c) and corrosion behavior of Fe-25at%Al alloys were investigated. The raw materials were arc-melted in vacuum and then subjected to the following heat treatments to maximize the DO_3 order : homogenized at 1000℃ for 48hrs, slowly cooled to 500℃, and held at that temperature for 24hours. Results showed that the B addition to Fe-25at%Al alloys does indeed refine the grain and change from intergranular to transgranular fracture mode at room temperature, indicating a strengthening of grain boundaries. The Fe-25at% Al-1at% B-3at% Si alloy showed the highest T_c(△T_c=150℃) in this work. However, the effectiveness of Si in raising T_c decreased with more than 5at% Si additions combined with B. Since the preferential corrosion occurs at the precipitates, the corrosion resistance decreased due to the increased amount of precipitates with alloying additions.