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
We present a model which predicts the critical free volume concentration of shear banding instability in metallic glasses(MGs).Fl-om the stability map,this model demonstrates that the prediction of shear band thicknes...We present a model which predicts the critical free volume concentration of shear banding instability in metallic glasses(MGs).Fl-om the stability map,this model demonstrates that the prediction of shear band thickness is valid only for a short time after shear instability,and the diffusion of defects should be included in the mature shear band in MGs.The results agree well with the experimental observations and simulations.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）.
基金Supported by the National Natural Science Foundation of China under Grant No 50801026Scientific Research Fund of Hunan Provincial Education Department(No 09B030)the Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province.
文摘We present a model which predicts the critical free volume concentration of shear banding instability in metallic glasses(MGs).Fl-om the stability map,this model demonstrates that the prediction of shear band thickness is valid only for a short time after shear instability,and the diffusion of defects should be included in the mature shear band in MGs.The results agree well with the experimental observations and simulations.
