Advanced Materials Research Vols. 399-401

Abstract: Damping capacities of the annealed nodular cast iron dense bar produced by horizontal continuous casting were measured by Dynamic Mechanical Analyzer. The relation of damping capacities with vibration amplitude, frequency and temperature was analyzed to investigate the damping mechanism of the alloy. The results show that the damping capacities increase with increasing temperature and frequency. The internal friction spectra exhibits two internal friction peaks at about 40°C and 150°C and caused by Snoek relaxation and Snoek-Köster relaxation, respectively. The maximum damping capacity can be obtained at about 63Hz. The damping is positive amplitude-dependent, whereas critical amplitude exists where the damping increases dramatically. The temperature-dependent damping results from the superposition effect of point-defect damping, grain boundary damping and interface damping, while dislocation damping is predominant in the frequency dependent damping. The amplitude dependent damping can be interpreted by G-L theory.

Abstract: By analysis of TWIP Steels with different manganese content, the results showed that the microstructures and properties had been changed with different Mn content. The elongation of the tested steel with 22.5% Mn was high for 55.5 % and n value of that reached to 0.360. When Mn content of the tested steel was 17.9%, the yield and tensile strength were higher and its elongation was lower for the tested steel than that of the tested steel with 22.5% Mn. The microstructures of the tested steel with high Mn content were austenite before and after being stretched at room temperature. Mn content was decreased and the microstructure of the tested steel after being stretched had a small amount of martensite transformation at room temperature. That is to say, double effect with TWIP and TRIP had occurred, but TWIP effect was dominant. TWIP effect increased plasticity and strain hardening capacity to improve formability. TRIP effect was mainly to improve strength so as to further attain the strength of the tested steel.

Abstract: With the aid of optical microscope, transmission electron microscope, scanning electron microscope, the processing and chemical composition on the microstructure and mechanical properties of low alloy wear resistance steels have been investigated. The results show that by multi-alloying design and TMCP processing the low alloy wear resistance steels has good synthetic properties. The lath martensite, multi phase microstructure composed of bainite and retained austenite film could be obtained after direct quenching. The lath martensite with retained austenite shows better wear resistance than bainite. Under the two bodies abrasive wear condition the characteristics of worn surface reveals that the main wear mechanism is micro-cutting.

Abstract: Microstructure of X80 pipeline steel with different hot rolling process was compared using Optical microscopy (OM), Bulk X-ray texture and micro orientation analysis was carried out by Orientation distribution function (ODF) and Electron back-scattered diffraction (EBSD), to analyze the various texture components of the pipeline steels under two different rolling processes. The results show that the final microstructures under the two schedules both present typical acicular ferrite characteristic. On the other side, the corresponding textures were found mainly comprised of two fibers in the rolling and normal direction in hot rolled X80 steel plate, there were obvious {112} , {110} , and {111} fiber, which seemed to be related with the mechanical properties anisotropy. Therefore, the influences of the microstructure and texture on the anisotropy were also discussed in this paper.

Abstract: The effect of austenitizing temperature, heating time and tempering temperature on hardness and impact toughness of low chromium white cast iron was studied by orthogonal test. The optical microstructure was used to analyze the reasons of changes on mechanical properties. The results showed that the hardness increases at beginning and then decreases with the increase of each parameter, high impact toughness can be obtained at high tempering temperature and high austenitizing temperature, the descending order of influence on hardness and impact toughness is austenitizing temperature, heating time, tempering temperature.

Abstract: FSW have advantage as defect such as porosity, metallic compounds decrease than other welding process. So, FSW was researched about low melting point materials. However, welding of high melting point and high strength materials attract attention because of high mechanical properties was needed due to industrial development. In this study, FSW is enforced using the kind of high melting point materials as SS400(SPHC). However, the tool must have super heat-resisting and abrasion resistance. So, WC-X%Co tool was manufactured by SPS method. The result, welding is successfully practice using WC-X%Co tool to 50m without fracture of tool.

Abstract: The theoretical performances of NEPE (nitrate ester plasticized polyether) propellant with and without ADN were calculated with minimum free energy method. The burning characteristics and the thermal decomposition of propellants were determined by nickel chromium wire method and TG- DTG, respectively. The SEM of NEPE propellants and the mechanical sensitivity were also detected. The results show that the specific impulse and the adiabatic flame temperature are increase with an increase in the content of ADN oxidizer. The burning rate and pressure exponent of propellant with a change of pat content of ADN can be boosted higher than those of the AP formulations.

Abstract: Self-supporting film of single-walled carbon nanotubes (SWNTs), also known as SWNT paper, is held together by Van der Waals force without any chemical binders. Prepared by vacuum filtration method, SWNT paper was then decorated wirh polypyrrole (PPy) through pulsed potentio amperometric polymerization. The results indicated that the SWNT paper had a typical network structure, after polymerizing PPy, cauliflower-like structure was observed on the surface of SWNT ropes. The composite thin film has good cyclic voltammetry (CV) property and the specific capacitance wass ca.420Fg^-1 , which was much larger than that of pure SWNT paper.

Abstract: The effects of different processing conditions (pressure, holding time and temperature) on the impregnation/consolidation quality of CF/PEKK composite were investigated using compression molding process. Microscopic investigation of cross-sections, density measurements and flexural mechanical properties were used to examine the quality of impregnation and consolidation. A qualitative model to describe the impregnation and consolidation process of this material was developed. The model predicts the variations of void content during consolidation as well as the holding time, moulding temperature and pressure required to reach full consolidation. Good agreement between theoretical predictions and experimental data was achieved. Optimum processing conditions can be determined based on selected void content.

Abstract: Removed due to author request.