Advanced Materials Research Vols. 146-147

Abstract: The uniformity of the mechanical properties, especially elongation and impact toughness, were compared between steel A, which was deoxidized with Ti-Zr, and steel B, which was deoxidized with Al. Microstructural observations, energy dispersive X-ray spectroscopy and X-ray diffraction analyses were conducted using an optical microscope, a scanning electron microscope and a transmission electron microscope, respectively. Results showed that sub-micron and nano-sized complex oxides were obtained by the combined deoxidation of Ti-Zr. The stability of the mechanical properties of steel A was better than that of steel B. The elongation and impact toughness of steel A were enhanced relative to those of steel B. This was attributed to spheroidization and the dispersed distribution of MnS inclusions in the matrix of steel A.

Abstract: Composition segregation and microstructure nonuniform of H13 steel have been obviously improved though adding nitrogen element. The microstructure and property of H13 steel with nitrogen contents of 0, 0.021%, 0.058% and 0.085% are studied under various quenching and tempering states. Dual quenching that is quenching between 1000~1010°C twice is employed in order to increase the tensile strength and hardness of coupons. The temperature and time are explored for improving the toughness under optimal quenching treatment. For extruding die steel, the tensile strength can reach a satisfactory level and impact toughness are met the requirements of NADCA at the temperature.

Abstract: Both the critical conditions and evolution of dynamic recrystallization behavior for a Nb-Ti microalloyed 3.5Ni steel were carried out by isothermal compression deformation on a Gleeble-3500 thermal simulator. Results show that the critical conditions of dynamic recrystallization behavior deformation of 30 % at 1050 °C, and the accumulative deformation for full dynamic recrystallization is 50 % at a strain rate of 1 /s. Accordingly, proposals on how to roll 3.5Ni steel were made.

Abstract: The Fiber Bragg Grating (FBG) sensor’s temperature sensitivity which is influenced by the metal-coated material and thickness was presented. The accurate equation was gotten according to the elasticity and fiber sensor theory. As indicated by the experiment, the changeable curve of the temperature sensitivity between theory equation and experiment is identical. And the FBGs sensitivities can be improved to 3~20 times.

Abstract: "Poly(trimethylene terephthalate) (PTT) shape memory fabrics" have excellent shape recoverability, whose clothes are easy to take care. In order to study the mechanism of “PTT shape memory fabric"’s shape recoverability, test of removing yarns from fabrics and comparing their crease recoveries with those of fabrics was designed. Results showed that crease recovery ratios of "PTT shape memory fabrics" were about 36%, while those of yarns removed from them were nearly 80%. Therefore, the results revealed that PTT yarns had good recoverability, however, the high inter-filament frictional forces in the fabric offerring by tight weave structures prevented PTT yarns from recovering. When the applied force was large enough to overcome frictions between filaments, the fabric gained sufficient mobility, coupled with PTT filaments’ excellent elastic recovery properties, and gave excellent fabric crease recovery. Moreover, new test method was designed independently to test different kinds of yarns’ crease recovery angles, results had proved once more PTT yarns had good elastic recovery, and their crease recovery ratios were close those of wool yarns, while the crease recovery of natural silk and cotton were the worst.

Abstract: In the present work, intermetallics Fe3Si and Fe3 (Si1-xAlx) (x=0.33, 0.67, 0.80) produced by arc melting, were evaluated regarding the oxidation at 900°C in air. The test preformed was the isothermal and cyclic oxidation. The microstructures of oxide films were analyzed by XRD, SEM, EDS, EPMA. The result showed that the four kinds of intermetallics had good oxidation resistance at 900°C.The addition of Al element can increase the oxidation resistance of Fe3Si based intermetallics. The oxidation kinetics of the four intermetallics follows the rule of the parabola. The main oxidation product of Fe3Si is SiO2.The kinetics of oxidation reaction is mainly controlled by Si diffusion. The oxidation product of three Al alloying Fe3Si based intermetallics is Al oxide. Al moves outward from the substrate to form a protective oxide film which restrained the diffusion of Si and Fe outward.

Abstract: The effects of [Si], [Ti] content on viscosity, melting temperature, and flow properties of hot metal were studied in the laboratory in allusion to the feature that hot metal bearing Ti becomes viscous easily. The solubility of titanium in molten iron was calculated with thermodynamic and relationship between solublity and temperature was disscused. The results show molten iron becomes viscous mainly controlled by the dissolution and precipitation of titanium. [Si] has a weakening effect on the solubility of titanium. Titanium will have less influence on the viscosity of hot metal whenΣ [Si+Ti] content is about 0.6 % and [Ti] content is below 0.29%. The choice of appropriate blast furnace temperature is the crux of avoiding hot metal containing titanium becomes viscous, hot metal pit adhesion, slag iron is difficult separation and so on.

Abstract: Carbon fiber embedded carbon aerogel (CFECA) was fabricated through simple addition of small organic gelators to the precursor formed by furfural and resorcinol. The surface area of the obtained CFECA decreased compared to that from the precursor without small gelator, but the electrical conductivities of the CFECA increased obviously. The maximum conductivity of the CFECA can reach 2.55 × 105 S/m which is more than three times as that of the referenced common carbon aerogel. The formation of CFECA was characterized by SEM as well as TEM observation.

Abstract: Pure 316L powder is used to mix with an additive to prepare a powder mixed paste. 316L honeycombs were fabricated by extruding the powder mixed paste, then dried and sintered. The volume shrinkage and the apparent density of extruded honeycombs after drying and sintering were measured. The effect of sintering temperature on the volume shrinkage, the apparent density and the structure of honeycombs had been studied. The results show that the volume shrinkage and the apparent density of sintered honeycombs increase with sintering temperature from 1120°C to 1200°C , the volume shrinkage varying from 42% to 57%, and the apparent density from 1.9 to 2.9g/cm3 for 80% solids fraction. The volume shrinkage decreases and the apparent density increases with solid fractions increasing. The structure of sintered honeycombs consists of matrix phase α-Fe(Cr,Ni) , complex compounds of silicon, oxygen and inclusion elements. There is oxide film forming on surface of sintered honeycombs.

Abstract: First, the fundamental characteristic of recycled concrete aggregate wasstudied. Then, the recycled concrete spiciemen with different maximum size was tested. The results showed that: the apparent density and bulk density of recycled concrete aggregates was smaller than the natural rock, but the moisture content, crushed index, water absorption was higher. The workability of recycled concrete improved with increase of water and fly ash, but its strength decreased as the increase of water and fly ash. The research on performance and strength of recycled concrete aggregate will provide certain theoretical basis in the application process.