Advanced Materials Research Vols. 139-141

Abstract: Brazing diamond wheel was carried out via laser in an argon atmosphere. The interfacial microstructures among brazed diamond, the filler alloy and matrix were analyzed by scanning electron microscopy (SEM), energy dispersion spectrometer (EDS) and X- ray diffraction (XRD). The formation mechanism of carbide layers was also discussed. Finally, grinding examination of the grinding wheel was carried through. The results show that diamond can not fall off from the wheel even at heavy duty conditions.

Abstract: MCM-41 functionalized by 3-aminopropyltriethoxysilane (APTMS) and 3-chloropropyltriethoxysilane (CPTMS) was synthesized, which had been used to improve the physicochemical properties of mesoporous silica to controlled ibuprofen delivery. Samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms and Fourier transform infrared (FT-IR) spectroscopy. Characterized results demonstrated that organic groups were successfully grafted onto the samples, and the mesoporous structure of the synthesized material was maintained. The results of ibuprofen release exhibited that the introduction of CPTMS greatly retarded the ibuprofen release rate, and an accumulative release achieved approximately 13.2 wt% over PClMCM-41 after 32 h. However, the introduction of APTMS greatly promoted the ibuprofen release rate, and the release of ibuprofen could increase to 26.6 wt% over PNH2MCM-41 at 32 h. Those results suggested that ibuprofen release rate could be well modulated by changing the grafted organic group.

Abstract: The effect of Ce2O3 on the fabrication of the Al-Ti-C-RE refiner prepared by adding a powder mixture of potassium titanium fluoride and carbon into the aluminum melt was studied by means of the OM, XRD, ESEM and EDAX etc. It found that the addition of Ce2O3 increases the reaction rate between the potassium titanium fluoride and carbon during the fabrication of the Al-Ti-C-RE refiner making the Al3Ti and TiC phases well distributed. Moreover, the Ce2O3 is an intensive kind of the surface activation element strongly sticking to the Al3Ti phase after reacting on the master alloy observed by ESEM, which formed a new rare earth compound phase [AlTiCe] and accelerated the synthesis rate of TiC particles. And adding 0.15wt% Al-Ti-C-RE alloy can refine the pure Al strongly and remarkably, in which the grain size of pure Al is lower than 94.2μm. When the holding time of refining exceeded the 120 minutes, the refining effect on the pure Al has not faded remarkably, which proves the Al-Ti-C-RE prepared by the Ce2O3 have long-life and stable refining effects.

Abstract: In this paper, the low alloy bainite ductile cast iron has been obtained by a new heat treatment technique of the step austempering in room-temperature machine oil. The effects of element boron, manganese and copper on structure and mechanical properties of the bainite ductile cast Iron in above-mentioned process are investigated. The phenomenon, hardness lag of the alloyed bainite ductile cast Iron, has been discussed. It shows that after the step austempering in room-temperature machine oil, the hardness will increases with the time. It is found that boron and manganese can increase the hardness and reduce the impact strength while copper can increase the impact strength. The results show that reasonable alloyed elements can improve mechanical properties of the bainite ductile cast Iron. Essentially, hardness lag of the alloyed bainite ductile cast Iron is resulted from solute drag-like effect.

Abstract: This paper studied the pulse generator and conductive device between metal wire and electrode for electroplastic wire drawing. We adopted the powerful GTR module on the design of the pulse generator, which makes a great superiority in the pulse waveform. The experimental results show that the design project is feasible and effective. In this paper, we displayed three types of conductive device between metal wire and electrode. According to the results of the experiments, the advantages and disadvantages of the three types of conductive device were discussed. Moreover, we also discussed the selection principles and methods for electrical parameter during the course of electroplastic drawing. Theoretical analysis and the experimental result indicate that it is advisable to use larger current density as much as possible, while try to decrease pulse width and frequency.

Abstract: A rapid-solidified hypereutectic Al-21Si-0.8Mg-1.5Cu-0.5Mn alloys strips has been prepared by single roller melt-spinning. The effects of solution technology on the microstructures and properties of the strips have been investigated by SEM, TEM. The results showed that the nucleation and growth of primary silicon are suppressed and α-Al is nucleated which prior to eutectic. The Cu, Mg and Mn are all supersaturated solution in α-Al. The major part of Si solution in α-Al, and the rest are precipitated by the micro-nanocrystals eutectic silicon. The metastable microstructures of micro-nanocrystals hypoeutectic are formed. And in the solution process, Si are precipitated from the matrix and gradually aggregate up to form small particles distributing in the matrix with the heating time. At 480°C for 100 minutes followed by quenching in water and a natural aging for 96h, the finer and more roundness of silicon particle and the maximum Vickers hardness are formed.

Abstract: The experimental data about concrete incorporating perlite admixture revealed that perlite admixture in content of 10%-20% replacing cement in equal mass enhanced effectively the workability, late-age mechanical strength and durability for concrete. The railway sleepers made of concrete with perlite admixture substituting for 20% cement were probingly produced in production line of manufactory without any modification to the conventional equipment or procedures. The summary was concluded that the concrete sleepers with 20% perlite admixture not only have met requirement of product quality, but also far better than demand of product quality on fatigue resistance, meanwhile prior to reference concrete sleepers without mineral admixture on major properties, such as fracture resistance. Consequently, the concrete sleeper considerably requires less maintenance and offers a longer service and reduced life-cycle costs.

Abstract: The population and size of porosities in three kinds of cast aluminum alloys, i.e. A713, A356T6-1 and A356T6-2, were statistically measured using a commercial software Spirit, and several distribution functions were tried to fit the cumulative pore size distribution data. It was found that a general extreme value (GEV) distribution function was the most appropriate function to quantify the cumulative pore size distribution in these cast aluminum alloys. The stress-number of cycles to failure (S-N) curves of these alloys were characterized by four point bend fatigue testing on MTS810 materials testing system, with the parameter f=20Hz, R=0.1, and in ambient air. The fatigue strength of A713, A356T6-1 and A356T6-2 aluminum alloy was measured to be 94.5 MPa, 150.6MPa and 117.3MPa respectively. The fatigue properties of these alloys could not be evaluated just by population and size distribution of the pores, the microstructure state, shape and position of pores, and other weakest links that may initiate a fatigue crack should be taken into account synthetically.

Abstract: LPMC specimens were burned in an oven at 500oC for 3h to obtain the fiber images by a scanner. The fiber distribution and orientation was analyzed using MATLAB software. And the effect parameters and controlling methods on fiber orientation and mechanic properties of molded parts were studied, too. Results showed that when the viscosity of LPMC sheet was 5×106cp , the feeding area was 60% and the velocity of mould closing was 1.0 mm/s, the uniformity of fiber distribution was optimum. And proper velocity of mould closing (1.0 mm/s) could decrease the fiber orientation. In addition, the flexural strength (185MPa) and flexural modulus (14.2GPa) of LPMC specimens paralleled the fiber direction were much higher than vertical one (75.2MPa, 6.9GPa).

Abstract: The microstructure of Mn-Mo-Nb-B microalloyed steel was investigated under different cooling rates after austenitic deformation by using thermo-simulation test, hardness measurement, metallographic and TEM analysis. The experimental results show that most constituents are mixed bainite ferrite and granular bainite at the cooling rate of 10 oC-50 oC /s. From the CCT curves, only polygonal ferrite and martensite could be obtained through the very slow and rapid cooling, respectively. The hardness of specimens keeps almost unchanged when cooling rate reaches above 10 oC /s (the utmost cooling rate is 50 oC /s in this simulation). Hence, the microstructure uniformity is attained, that is to say, the transformation products are insensitive to the cooling rates, which attributes to the appropriate component design and optimized hot simulation. Another experimental phenomenon is that the fine scale (<5 nm) carbonitride precipitates were observed in the relatively lower cooling specimens.