Ni-25Al-15Cr （atomic percent, %） alloy was directionally solidified （DS） under argon atmosphere in an Al2O3-SiO2 ceramic mold by standard Bridgman method. The microstructure of the as-fabricated alloy was studied ...Ni-25Al-15Cr （atomic percent, %） alloy was directionally solidified （DS） under argon atmosphere in an Al2O3-SiO2 ceramic mold by standard Bridgman method. The microstructure of the as-fabricated alloy was studied using optical microscope, X-ray diffractometer, and scanning electron microscope. The alloy consisting of dendritic β- NiAl phase, interdendritic γ/γ′ phase, and transient layer γ′ phase, has been investigated. This alloy exhibits superplastic deformation behavior at 1 273-1 373 K over an initial strain rate range of 8. 35×10 ^-4 -1. 67×10^-2s^-1. The maximum elongation of 280% with strain rate sensitivity index m= 0. 22 was obtained at the temperature of 1 323 K and an initial strain rate of 8. 35×10^-3s^-1. Transmission electron microscopy （TEM） observations indicate that the superplastic deformation stems from the balance between high resistance （by dislocation sliding） and strain softening （by dynamic recovery and recrystallization）.展开更多
文摘Ni-25Al-15Cr （atomic percent, %） alloy was directionally solidified （DS） under argon atmosphere in an Al2O3-SiO2 ceramic mold by standard Bridgman method. The microstructure of the as-fabricated alloy was studied using optical microscope, X-ray diffractometer, and scanning electron microscope. The alloy consisting of dendritic β- NiAl phase, interdendritic γ/γ′ phase, and transient layer γ′ phase, has been investigated. This alloy exhibits superplastic deformation behavior at 1 273-1 373 K over an initial strain rate range of 8. 35×10 ^-4 -1. 67×10^-2s^-1. The maximum elongation of 280% with strain rate sensitivity index m= 0. 22 was obtained at the temperature of 1 323 K and an initial strain rate of 8. 35×10^-3s^-1. Transmission electron microscopy （TEM） observations indicate that the superplastic deformation stems from the balance between high resistance （by dislocation sliding） and strain softening （by dynamic recovery and recrystallization）.
