Advanced Materials Research Vols. 287-290

Abstract: By means of magnetron sputtering, the Fe-Y coatings containing 15.4%, 20.7% and 32.7% Y (atom fraction), were deposited on stainless steels. The sputtered coatings were investigated by discontinuous weigh measurement. The results indicate that the oxidation kinetics can be divided into three stages, of which the first and second stages obey the parabolic rate law, while the oxidation kinetic curves of the last stage nearly exhibits horizontal lines. With the increase of the content of Y, the oxidation rate obviously increases. The external scale of the three kinds of alloys is substantially similar. After 24-h oxidation at 800 °C under 1 atm of air, the surface of sputtered coating is mainly transformed into three types of oxide scales, of which the thin outermost layer was Fe2O₃, the innermost is YFeO₃ mixed with double oxides including FeO or Fe3O₄. Single Y₂O₃ layer was not formed on the surface or in the alloys. The results were disscussed by taking into account the defects in the metal oxide, the self-diffusion of the elements in the alloys, and the low diffusion of yttrium in iron.

Abstract: The microstructure and properties and wear resistant of carbide free bainitic casting steel were studied by using of OM, TEM, XRD, impact test and abrasion test. The results showed that after normalizing at 1080°C and tempering at low temperature the microstructures consisted of bainitic ferrite, remaining austenite and no carbides with combination properties of strength and toughness. After tempering at 250°C the tensile strength was 1667MPa, Rockwell hardness HRC49 and impact ductility A_KU 36J, respectively. This new casting steel by normalizing at 1080°Cand tempering at 200°C had better wear resistance than that of high manganese steel under the same test conditions, moreover the reason was analyzed.

Abstract: The microphotograph, size distribution and chemical composition of second phase particles in Q195 steel were characterizated using SEM and EDS. In order to observe the nanometer grade second phase particles, SEM with high resolution should be used. Whether can be second phase particles discovered lies on the preparation method of samples. This method is easier for sample preparation, lower cost, more efficient than TEM method.

Abstract: Structural lightweight aggregate concrete (LWAC) members have demonstrated greater fire endurance periods than equivalent thickness members made with normal-weight aggregates. Superior performance is due to a combination of lower thermal conductivity, lower coefficient of thermal expansion, and the inherent thermal stability developed by aggregates that have been exposed temperature greater than 1050°C during preprocessing. Furthermore, LWAC exhibits relatively high thermal insulating value, of which the thermal conductivity can be half as much as that of ordinary normal-weight concrete (NWC). Therefore, the main objective of this paper is to implement fire resistance testing for structural and non-structural elements made of LWAC and NWC to assess and compare their fire behavior.

Abstract: The ageing of copper foils and Copper foils-surfaced in UV rays are studied by 3D Video, SEM, EDX, which shows that copper foils and Copper foils-surfaced are in different level of ageing; embossment and crack which are the most obvious aging characteristics found by SEM, obviously, the ageing velocity of copper foil -surfaced is higher; The sulfur is found in the powder-like material around the embossment on the surface of copper foils by EDX, which indicates that sulfur is involved in the process of aging.

Abstract: The effect of improper heat treatment progress on the structure and properties of P91 steel was studied. Results showed that under aircooling conditions, although the normalization temperature is beyond conventional range, the hardness meets the requirements of ASME standard, and the microstructure appear a gradual transition from equiaxed ferrite with carbide precipitates to tempered martensite. In addition ,when normalization temperature was as high as 1150°C and 1250°C, there is an characteristic morphology of coarse martensite laths and some of them are orthogonal to each other. When normalization cooling rate is slowly at 1°C/min, the hardness dropped under the lower limit at reduced normalization temperatures and the microstructure consist of polygonized ferrite and carbide precipitates. SEM and TEM observation indicated that with the increasing normalization temperature the ferrite morphology transforms from coarse polygonized to finer equiaxed, and carbide precipitates not only along boundaries but also within the grain, at the same tine rod shape carbides formed at 1000°C normalization.

Abstract: The Bauxite-based Homogenized Grog (BHG) was industrial producted using bauxite with about 70 wt.% Al₂O₃ as starting materials and its properties were tested. Through comparing with high-grade bauxite clinker, the applications in LCCs of BHG and bauxite clinker were discussed. The results showed that the BHG with mullite as chief phase, with consistent components and structure and properties using middle or low grade bauxite as starting materials can been prepared industrially by homogenization process, vacuum-extrusion moulding and high-temperature sintering method. It also resulted that the BHG can replace competently high-grade bauxite clinker to apply in LCCs as coarses and the LCCs with BHG as coarses have more outstanding properties.

Abstract: The type and properties of the grouting materials contribute great impact on the grouting effect. The new grout with hydrated lime, fly ash, bentonite, sand, water and water reducer as materials was developed, and the raw material requirements and performance requirements of the new grout were ascertained. Some experimental results were illustrated on the fineness modulus of sand and water reducer dosage impact on the properties of the new grout. The preliminary application results in Shanghai and Soochow metro showed that the new grout played a very good role on the surface subsidence control both in fine clay soil and sand strata.

Abstract: In this paper, concrete was analyzed as a composite consisting of coarse aggregate, mortar matrix and interfacial transition zone (ITZ). Because permeability of each phase are not the same, ITZ will affect the concrete permeability. Effect of ITZ on the concrete permeability was studied by laboratory test and numerical analysis.The diffusion coefficient of ITZ, mortar,and concrete can be caculated by laboratory test. The results indicate that the diffusion coefficient of ITZ is far greater than mortar，which is about 40 times of mortar. The chloride ions diffusion ignoring ITZ and considering ITZ were simulated, the results show that the diffusion coefficient of concrete was bigger when the ITZ was considered, which was closer to the experimental results.