Cu-Zn 2元合金の凝固の進行に伴う脆化

抄録

Tensile strength and apparent deformation of solidifying binary Cu-Zn alloy castings were studied at various fractions of solid by use of a tensile test apparatus newly designed. The alloys complete solidification through four stages with increasing fraction of solid. The alloys in stage I with fraction of solid up to f_a have significant deformation and negligible strength. Those in stage II with fraction of solid f_a to f_b rapidly lower the deformation. Those in stage III with fraction of solid f_b to f_c minimize the deformation and have noticeable strength. Those in stage IV with fraction of solid f_c or more show rapid increase in both of deformation and strength (f_a<f_b<f_c). The α-phase alloys containing Zn up to 30 mass% have less apparent deformation in the extended brittle stage III than the β-phase alloys. The peritectic alloy has the maximum apparent deformation. Interdendritic fluid flow plays a significant role in the embrittlement during solidification. Changes in the tensile properties with increase of fraction of solid are explainable by the solid forming process and interdendritic fluid behavior.