Al-Si coated ultra-high strength steel（UHSS）has been commonly applied in hot stamping process.The influence of austenitizing temperature on microstructure of Al-Si coating of UHSS during hot stamping process and its...Al-Si coated ultra-high strength steel（UHSS）has been commonly applied in hot stamping process.The influence of austenitizing temperature on microstructure of Al-Si coating of UHSS during hot stamping process and its tribological behavior against H13 steel under elevated temperature were simulatively investigated.The austenitizing temperature of Al-Si coated UHSS and its microstructual evolution were confirmed and analyzed by differential scanning calorimetry and scanning electron microscopy.A novel approach to tribological testing by replicating hot stamping process temperature history was presented.Results show that the hard and stable phases Fe_2Al_5＋FeAl_2 formed on Al-Si coating surface after exposure to 930°C for 5 min,which was found to be correlated to the tribological behavior of coating.The friction coefficient of coated steel was more stable and higher than that of uncoated one.The main wear mechanism of Al-Si coated UHSS was adhesion wear,while abrasive wear was dominant for the uncoated UHSS.展开更多
P91 steel is an important bearing material used in nuclear power plants. The study of its mechanical degradation behavior is important for ensuring safe operation. The relationship between the dislocation density of P...P91 steel is an important bearing material used in nuclear power plants. The study of its mechanical degradation behavior is important for ensuring safe operation. The relationship between the dislocation density of P91 steel under different strains and the corresponding nonlinear ultrasonic parameter β was studied. The dislocation density of strained samples was estimated by X-ray diffraction. Nonlinear ultrasonic testing was conducted to evaluate β, showing that this value increased with increasing dislocation density induced by different tensile elongations. It was shown that the ultrasonic secondharmonic generation technique can effectively evaluate the degradation behavior of metallic materials, and the prediction of the residual life of bearing parts in service can be made based on β and the dislocation density.展开更多
In this work,the serpentine powders were sintered to make the serpentine-reinforced Al-matrix composites,and the microstructures of which were characterized by differential scanning calorimetry,thermal gravimetric ana...In this work,the serpentine powders were sintered to make the serpentine-reinforced Al-matrix composites,and the microstructures of which were characterized by differential scanning calorimetry,thermal gravimetric analyzer,and X-ray diffractometer.Scanning electron microscopy equipped with energy dispersive spectroscopy.Results show that the sintered serpentine powders were deeply absorbed on the worn surface and embedded in the furrows and scratches of the matrix,forming a self-repairing surface layer which reduces the friction coefficient.The surface layer coated by serpentine was compact,dense,and uniform with the friction time prolonged,compensating the worn loss and increasing the matrix mass.展开更多
基金the financial support from National Natural Science Foundation of China(Grand No.51475280)
文摘Al-Si coated ultra-high strength steel（UHSS）has been commonly applied in hot stamping process.The influence of austenitizing temperature on microstructure of Al-Si coating of UHSS during hot stamping process and its tribological behavior against H13 steel under elevated temperature were simulatively investigated.The austenitizing temperature of Al-Si coated UHSS and its microstructual evolution were confirmed and analyzed by differential scanning calorimetry and scanning electron microscopy.A novel approach to tribological testing by replicating hot stamping process temperature history was presented.Results show that the hard and stable phases Fe_2Al_5＋FeAl_2 formed on Al-Si coating surface after exposure to 930°C for 5 min,which was found to be correlated to the tribological behavior of coating.The friction coefficient of coated steel was more stable and higher than that of uncoated one.The main wear mechanism of Al-Si coated UHSS was adhesion wear,while abrasive wear was dominant for the uncoated UHSS.
基金Item Sponsored by National Natural Science Foundation of China(61171145,11274226)
文摘P91 steel is an important bearing material used in nuclear power plants. The study of its mechanical degradation behavior is important for ensuring safe operation. The relationship between the dislocation density of P91 steel under different strains and the corresponding nonlinear ultrasonic parameter β was studied. The dislocation density of strained samples was estimated by X-ray diffraction. Nonlinear ultrasonic testing was conducted to evaluate β, showing that this value increased with increasing dislocation density induced by different tensile elongations. It was shown that the ultrasonic secondharmonic generation technique can effectively evaluate the degradation behavior of metallic materials, and the prediction of the residual life of bearing parts in service can be made based on β and the dislocation density.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50975166 and 51475280)the Excellent Engineer Training Program (Metallic material engineering of Shanghai University) of Ministry of Education, China
文摘In this work,the serpentine powders were sintered to make the serpentine-reinforced Al-matrix composites,and the microstructures of which were characterized by differential scanning calorimetry,thermal gravimetric analyzer,and X-ray diffractometer.Scanning electron microscopy equipped with energy dispersive spectroscopy.Results show that the sintered serpentine powders were deeply absorbed on the worn surface and embedded in the furrows and scratches of the matrix,forming a self-repairing surface layer which reduces the friction coefficient.The surface layer coated by serpentine was compact,dense,and uniform with the friction time prolonged,compensating the worn loss and increasing the matrix mass.
