Search

Abstract A composite foil is proposed to join three-dimensional C f /SiC to Nb substrate, which is composed of Ti-Zr-Cu-Ni amorphous foil and Ti foil, in order to reduce the brazing temperature, meanwhile keep the high serving temperature. During the brazing process, the dissolution of Ti from Ti foil and Nb from substrate into the brazing alloy was discovered. Such dissolution contributes to a variational composition and microstructure of the brazing seam. The β-Ti eutectoid transformation was suppressed. A high content of the in-situ forming (Ti,Nb) solid solution phase was observed in the brazing seam after brazing process, which is considered to be favorable for the joint for its low elastic modulus and good deformability. Defect-free joints are successfully obtained in this work using this composite foil. The maximum shear strength of the joint is measured to be 121 MPa at ambient temperature, and 83 MPa at 600 °C, respectively. Highlights • The (Ti,Nb) solid solution phase ((Ti,Nb) ss) was in-situ formed. • (Ti,Nb) ss remarkably improved the deformability of joints. • Ti solid solutions markedly increased by increasing Ti content in brazing seams. • The shear strength of joints enhanced more than five-fold. [ABSTRACT FROM AUTHOR]

Abstract: AM-SC1 (Advanced Magnesium-Sand Casting Alloy 1) is a heat-resisting Mg-RE based alloy which has been widely applied in engine block. It would be an effective way to decrease the cost of the alloy by replacing Nd with Ca as addition. The effects of Ca addition on the microstructure and mechanical properties of the alloy were investigated by means of Brinell hardness measurement, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction and tensile tests at room and elevated temperatures. As the addition of Ca is 1.5%, the alloy shows the finest grain size of 16μm which also contributes to the highest hardness and strength of 62.1 HB and 148MPa, respectively. After T6 treatment (solid solution treatment at 500°C for 7h and aging treatment at 200°C for 20h), the morphologies of the phases in the Ca-containing alloys change from net-like to fine short-block and particle-like shapes, and its strengths at RT, 175°C and 200°C are correspondingly improved to 186MPa, 166MPa and 140MPa, respectively. [Copyright &y& Elsevier]

Abstract: Bi2S3 microcrystallites with three-dimensional (3D) superstructures were synthesized by the reaction of bismuth nitrate (Bi(NO3)3) with sodium O-isopropyldithiocarbonate (isopropyl xanthate, C3H7OCS2Na) at 80°C in N,N-dimethylformamide (DMF) solution without any surfactants. It was observed that Bi2S3 crystalline nanorods aggregated to urchin-like globules in the microscale when C3H7OCS2Na was slowly added to Bi(NO3)3 in DMF solution at 80°C, while cockscomb-like microspheres aggregated by Bi2S3 nanobelts with a typical width of ∼20nm were obtained if two precursors were mixed at room temperature and then heated to 80°C. Possible mechanisms for the formation of 3D Bi2S3 microcrystals were proposed. The structures of Bi2S3 crystals were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and laser Raman spectroscopy. [Copyright &y& Elsevier]

The effective characterization of the mechanical property degradation of turbine blades in service for an ultra-long-term had a significant impact on the service safety and maintenance decisions of turbine blades. In this study, the microstructure observation and mechanical property study of the K403 polycrystalline Ni-based superalloy turbine blade under four service times were carried out, using microstructure characterization methods to quantify the microstructure evolution of the superalloy at different parts of the turbine blade with increasing service time. The effects of the microstructure degradation of the superalloy under ultra-long-term service on the mechanical properties of the turbine blade were analyzed. The results show that the microstructural degradation characteristics of the superalloy turbine blades under ultra-long-term service were strongly correlated with the spatial structural characteristics of the turbine blades after service, and it was found that the carbon elements and other elements inside and at the boundary of the carbide showed regular migration behavior with the increase in service time. The regular influence of microstructural degradation of superalloy turbine blades under ultra-long-term service on their mechanical properties was demonstrated. These results can provide empirical support for the study of the predicted residual properties of nickel-based superalloy turbine blades under ultra-long-term service. [Display omitted] • Microstructure evolution of turbine blades under ultra-long-term service was studied. • Mechanical properties of turbine blades under ultra-long-term service were studied. • Influence of microstructure evolution on mechanical properties was studied. • Position-related microstructure evolution and mechanical properties was studied. • Quantitative study of carbide evolution with service time was performed. [ABSTRACT FROM AUTHOR]