Advances in Superalloys

Volumes 146-147

doi: 10.4028/

Paper Title Page

Authors: Zeng Wu Zhao, Bao Wei Li, Ming Wen, Yong Li Jin, Fu Shun Zhang
Abstract: In order to further improve utilization efficiency of Bayan obo Fe-Nb-RE complex deposit, selective reduction of Nb-bearing iron concentrate was achieved by using a reduction processes in reaction cylinder which is heated in tunnel kiln. The experiments were focused on investigating effects of reduction temperature and time on the reduction dynamics of Nb-bearing iron concentrate. The results show that the temperature at the centre of reaction cylinder is lower than its peripheral temperature. The local metallization ratio of the produced sponge iron ring varies from high, to low and to high level along its radius direction. With reduction temperature increasing, the metallization ratio of produced sponge iron is proportionally increasing, and the outer diameter of the sponge iron ring is gradually decreasing. The metallization ratio of the produced sponge iron is gradually increasing with the increase of reduction time.
Authors: Jin Tao Li, Guang Ming Xu, Jian Zhong Cui
Abstract: The effect of electromagnetic field on microstructure of roll-casting 5052 aluminum alloy sheet has been investigated and analyzed. The results indicate that imposing static magnetic field can refine the grains of 5052 aluminum alloy during the roll-casting; accordingly, imposing static magnetic field and alternating current at the same time, the grains are remarkably refined and equiaxed due to electromagnetic oscillation effect.
Authors: Su Yi Gu, Ji Hua Zhang
Abstract: The detailed investigation of internal friction and relative dynamic modulus has been carried out for the γ-MnFe alloys with 61.4at%~86.4at%Mn in the temperature range from -50 to 250 using LMR by means of force vibration method. The internal friction was found to exhibit in turn three peaks from higher temperature to the lower temperature on the internal friction-temperature curves. They are PA,PM and PT progressively. It can be concluded that PA may be connected with the stress-induced motion of magnetic domain. The PM was suggested to be originated from the stress-induced movement of interfaces between the fcc and fct phases. The PT is due to a relaxation process associated with the movement of the {101}-twin boundaries in the fct phase or fcc antiferromagnetic phase.
Authors: Yuan Cheng, Hong Ying Yu, Li Xin Zhang, Ying Wang, Xu Meng, Dong Bai Sun
Abstract: The stress corrosion cracking susceptibility of X80 pipeline steel was investigated in a simulated soil solution using slow strain rate tensile (SSRT) tests. The different potentials were applied in the tests. The fracture surfaces were observed using scanning electron microscopy (SEM). The X80 steel was susceptible to SCC in simulated solution. The SCC susceptibility had no apparent change with the anodic potentials applied. The fracture mechanism was anodic dissolution. However, the SCC susceptibility increased with the decrease of the cathodic potentials obviously. The cracking was induced by the Hydrogen diffusing into the metal.
Authors: How Ji Chen, Te Hung Liu, Chao Wei Tang
Abstract: The present study experimentally investigated the pre-failure and post-fatigue behavior of reinforced concrete (RC) beams constructed with lightweight aggregate concrete (LWAC) in comparison with that constructed of normal weight concrete (NWC) of the same compressive strength (40 MPa). A total of twelve RC beams were tested under different fatigue loadings. Based on the experimental observations, the midspan total deflection measured in the fatigue testing consisted of the elastic and plastic components. The mechanismof the two deflection components developed with load cycles was different. The experimental results showed that the fatigue resistance of LWAC beams was better than that of NWC beams for the same fatigue loading levels. It was reflected in both the lower evolution of fatigue damage and the smaller growth of midspan residual deflection. After 2 million cycles, an average increase in residual load capacity of about 8% was found in the NWC beams, while that in the LWA beams remained virtually unchanged.
Authors: Xiang Dong Huo, Zhang Guo Lin, Yu Tao Zhao, Yu Qian Li
Abstract: In order to develop low carbon bainitic Cr-B steel, experimental procedures including melting, thermal simulation study and laboratory hot rolling were adopted. The dynamic CCT diagram was established, microstructure and properties of experimental steel were also analyzed. The transformation temperature of experimental steel lies between 650~400°C and final microstructure changes fromquasi-polygonal ferrite, granular bainite to lath bainite as cooling rate increases from 0.2 to 50°C.s-1. The microstructure of steel plates, air cooled or water cooled to 530°C then air cooled, is mainly composed of granular bainite and quasi-polygonal ferrite, and the large size islands in granular bainite are responsible for the low strength and poor toughness. However, steel plate with lath bainite, water cooled to roomtemperature, boasts high yield strength (672MPa) and superior impact toughness (127J at -20°C). Therefore, it is feasible to produce low carbon bainitic Cr-B steel with high strength and good toughness through controlling cooling parameters.
Authors: Xi Chang Shi, Xiang Xiao, Bai Zhen Chen, Wei Shang
Abstract: A novel process of micro-arc oxidation (MAO) on AZ91D magnesium alloy is investigated in a Na2SiO3-NaOH-montmorillonite-EDTA-acacia gum electrolyte solution. The morphologies, elements distribution, phase components of the coatings are characterized by SEM, EDS and XRD. And CHI600 electrochemistry corrosion workstation is employed to investigate the property of corrosion resistance of the coatings. Furthermore, the anti-corrosion behavior is analyzed immersed in 3.5 wt. % NaCl solution. The results reveal that the ceramic coatings have the relatively dense and uniform in thickness and the silicon element tends to present primarily in the outer region of the coatings. The XRD results indicate that the oxide films are mainly composed of Mg2SiO4 and MgAl2O4 phases. The immersion results show that the corrosion resistances of the ceramic coatings on AZ91D magnesium surface are better than the magnesium substrate.
Authors: Xin Liu, Xiao Dong Kong
Abstract: Five Al-Bi-Sn-In-Ga alloys with different Bi content were designed and prepared. Their electrochemical properties in 3% sodium chloride solution, the distribution of alloying elements and surface morphologies were studied by means of loss of weight method, polarization curve, electrochemical impedance spectroscopy (EIS) and energy spectrum analysis. The results indicate that, a good deal Bi and other alloying elements form new phases which exist in grain boundaries in the form of dot or granule, and Bi rich regions are prone to become the inductive points of pitting corrosion. Moreover, there is a certain linear relation between Bi content and the self corrosion rate.
Authors: Li Hua, Gia Kuan Yang, Hong Quan Zhang
Abstract: Due to lead-free pressure, Sn-Ag-Cu solder is regarded as the potential candidate. However, higher melting point and faintish soldering restrict its wide application. Metal or rare earth metal doping can improve its soldering. In this thesis, Ge doping in Sn-3.0Ag-0.5Cu (SAC) solder were discussed. Effect of metal Ge doping on electrochemical corrosion behavior of lead-free SAC solder in 3wt.% NaCl solution were investigated by potentiodynamic polarization measurement. The electrochemical migration(ECM)attributed to dendrites growth were employed by the salt immersion experiment, and the oxidation characteristic was researched by thermo gravimetric analysis(TGA). The surface morphology and elemental composition of various elements in the doped solder were determined by analyzing the corrosion product or dendrites formed on the specimen by SEM, EDAX techniques. The results showed that the dendrite growth can be accelerated after Ge doping comparing to Sn-3.0Ag-0.5Cu solder. The shapes of dendrites were completely different before and after Ge doping, the fore looked like as tree leaves, the latter looked like little stem, all dendrites grown from different kind of material can be well differentiated by the help of their fractal dimension. EDAX result showed that the content on dendrites of Sn-3.0Ag-0.5Cu solder doping with Ge were mainly Sn, only little Cl- and Na+. Corrosive experiment showed that the corrosive current density (Icorr) increased with Ge content increasing when the percent content of Ge was less than or equal to 1%, the contrary effect suitable to that Ge doping larger than 1%. TGA result showed that Ge doping could improve the anti-oxidation capacity of SAC solder comparing to no doped solder. It provided a good technical support to develop a new lead-free solder substituting for Sn-37Pb.
Authors: Wei Lin Zhao, Hui Huang, Zhen Lin Wang
Abstract: The effects of the surface roughness on electro-deposition properties of the special nickel electroplating coating for the 45# steel were investigated. The results indicate that the surface roughness has great effects on the corrosion resistance and the surface hardness of the coating, the adhesion force between the coating and the substrate. Among the three 45# samples with different surface roughnesses, the sample with moderate surface roughness (Ra≈0.1um) has the relatively higher corrosion resistance, surface hardness and adhesion force than the samples with higher and lower surface roughness.

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