Advanced Materials Research Vols. 146-147

Abstract: The growth process of synthetic diamond single crystals under high-pressure and high-temperature (HPHT) was investigated using acoustic emission (AE) technique. And AE parameters corresponding to growth process were analyzed. However, the AE features of diamond growth are relativelyweak and easily obscured by other AE sources. So the fast Fourier transformation (FFT) was used to calculate the frequency spectra of AE signals for identifying different AE sources. The results showed that the variation of AE counts and energy is in a good agreement with the formation process of synthetic diamond crystals. And the AE signals pronounced from diamond growth are concentrated in the frequency range from 100 to 250 kHz. Thus, AE technique is an effective way to monitor and study the diamond growth, and the frequency analysis can be a useful way to identify different AE sources.

Abstract: Mg-6Zn-0.6Zr magnesium alloy (ZK60) was extruded by equal channel angular processing (ECAP) equipment via 2, 4, 6 passes at 400°C. The corresponding microstructure and hardness were examined. The change of the crystal plane in this processing was analyzed by X-ray diffraction. The results show that, ECAP favors recrystallization and refines grains with the increase of pass times. The grains are significantly refined to 10um after 6 passes and the hardness is improved to 79.8HV after 4 passes.

Abstract: In this paper, effects of solid solution treatment temperature on microstructure and tensile properties of casting SAF 2507 super duplex stainless steel were researched by means of optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and tensile test. The results indicate that the amount of γ phase increases according to a linear relationship f(g ) = -0.134T +159.94 during the temperatures from 1100°C to 1250°C. Tensile properties of casting SAF 2507 super duplex stainless steel fluctuate with solution temperature change. Austenitic grain size and morphology are the most important factors on tensile property. The tensile strength is the highest owing to the finest austenitic grain at the solution temperature of 1150°C. The elongation is related to the fracture mode. At 1100 , elongation ration is highest because of the ductile fracture.

Abstract: In this paper, continuous running test was conducted using the disk drive spindle micromotors used in automobiles DVD. The commutator and brush were made of AuAg/AgCuNiCe/Cu and AgPd/CuNiSn layered composite respectively. In order to investigate the wear behavior of the commutator, the micromotors were dissected after ran continuously for different time. The worn surface of the commutator and the brush were characterized using an SEM equipped with EDS. Also, the cross section of the commutator was analyzed. It was shown that the AuAg layer was not totally worn off until 1500 h of running test. AuAg transferred from the commutator to the brush. It was interesting that Au was found on the silver layer where the depth of wear crater surpassed the thickness of the original AuAg layer. Small particles enriched in Cu, Ni and Ce were observed on the contact surface of AgCuNiCe layer, which was thought to improve the wear resistance of the commutator. The wear mechanism was mainly slight abrasion whereas no effect of arc was found on the sliding contact area.

Abstract: A macro-scale ProCAST and a meso-scale Cellular Automaton Finite Element model (CAFE) are used to simulate the grain selection during solidification with different simulation conditions. To improve the efficiency of the spiral grain selector, the effects of spiral geometries, boundary conditions and nucleation parameters on the grain selection are investigated. Simulation results reveal that the spiral geometries affect the height where the single crystal occurs in the spiral selector when volume nucleation is neglected. The average orientation deviation and grain number is relatively insensitive to volume nucleation and thermal boundary conditions around grain selector, and the thermal boundary conditions in the top of grain selector being of lesser importance.

Abstract: Silicon is the most attractive for the largest theoretical insertion capacity of all known host materials except lithium metal. In this paper, the course of lithium insertion into Si material, especially of the first cycle, has been discussed. Anode phase structure, impedance and character, morphology is presented and discussed in this paper. Changes on different crystal lattices revealed the possibility that the structure collapsed firstly began on lattice (220). Distinct crack on the surface of silicon particles has been observed when the anode was discharged to 0.02V.

Abstract: Hot rolled Ti microalloyed steel with polygonal ferrite and granular bainite microstructure and 640 MPa yield strength has been developed in BOF-CSP process. By chemical phase analysis, XRD, EDS and high resolution TEM, the particle size distribution, morphology, composition, crystal structure of precipitates were identified. Results revealed the steel containing Ti exhibits fine and uniformly distributed Fe3C-type carbides, the amount of M3C particles less than 18 nm in size was 0.2565 mass %. The high strength of steel is attributed to the precipitation strengthening effect of Fe3C, the yield strength increment from precipitation strengthening of Fe3C calculated according to the formula by Olson and Ashby-Orowan attained 234.4 MPa.

Abstract: This paper deals with the accurate prediction of forming limit of a dome with a circular hole in two-stage stretch forming. Since this two-stage forming is a process of non-proportional deformation, a fracture criterion, which is capable to predict fracture limit of sheet metal under non-proportional strain path, is introduced. The limit dome height of steel blank is predicted by utilizing numerical optimization technique, in which the fracture criterion is used as a constraint function to avoid sheet breakage. The calculated result and the corresponding experimental result show that the fracture criterion can successfully predict the limit dome height in the two-stage forming while the classical forming limit diagram (FLD) overestimates it.

Abstract: The quadratic general rotary unitized design of two factors, the temperature and the time were used to study the influence of low-temperature to architectural membrane material. The tensile properties of architectural membrane material were tested after low-temperature treatment, and the mathematical models about breaking strength and elongation at break were built. The two mathematical models proved highly significant by F test, which indicates that the low-temperature environment has a distinctive influence on breaking strength and elongation at break of architectural membrane material. The results are kept to serve as a reference for the rational utilization of architectural membrane material in low-temperature environments.

Abstract: The non-isothermal experiments of TiO2 reduction to Ti(C,N) were conducted by a comprehensive thermal analyzer in Ar and N2 atmospheres. The mechanism of Ti(C,N) generation was analyzed and the kinetic parameters in different atmospheres were calculated. The results showed that Ti(C, N) formation process was controlled by interface chemical reaction, and the existence of nitrogen would favor the formation of Ti (C, N). TiC transforming into TiN occurred at a temperature above 1200°C.