Key Engineering Materials Vols. 575-576

Abstract: By adding sintering additives (CMS and nanoTiO₂), Ni-MF/Al₂O₃ composites were prepared by pressureless sintering. In order to ameliorate the combination between mullite fiber and alumina matrix, mullite fiber surface was coated with Al₂O₃ coating. To improve the property of alumina ceramic composite, Ni particles were chosen as toughening phase. For the preparation of composite, the optimum process was 10% MF, 13% Ni, and sintering temperature in 1400°C. The material performance can be effectively improved.

Abstract: The correlation between the deformation behavior and the microstructure of AZ31 magnesium alloy processed by as-extruded and ECAP is investigated in this paper. The grain size of as-extruded AZ31 magnesium alloy is about 30μm which dues to basal and twinning. Twinning is the main deformation behavior for as-extruded AZ31 magnesium alloy. The deformation of as-extruded is mainly caused by basal slip and twinning. The grains of ECAP are further refined to 6μm. With little amount of twins, the refinement of AZ31 magnesium alloy is caused by non-basal sliding. For ECAP precessed sample, grain boundary sliding happens and the proportion of high-angle grains are improved, which makes grain boundary sliding easier. The main deformation mechanism of ECAP is non-basal slip and grains boundary sliding.

Abstract: Under the condition of different magnetic induced intensity as1.5T, 2.0T and2.5T, AlTiZr particles reinforced 7055 aluminum matrix composites were subject to the magnetic impact processing. The structural evolution was observed by transmission electron microscope. The result shows that, magnetic impact processing can induce dislocation with different morphologies and increase the dislocation density. The enhancement of dislocation density and elastic interaction between them can cause the resistance of dislocation movement and improve the strength of material. The magnetic pressure may exceed the yield strength of special orientation crystal. The increased temperature induced by heat effect will lower the yield point further. It is useful to dislocation nucleation and movement.

Abstract: The microstructure, hardness and corrosion resistance of AZ91D alloy were investigated under different solution treatments and artificial aging conditions.When ascast AZ91D alloy was heat treated at 415°C by solution treatmentfor 12 h and artificially aged at 200°C, the volume fraction of precipitates increased with the aging time up to 10 h.When ascast AZ91D alloy was treated at 430°C by solution treatment for 12 h and artificially aged at 200°C for 10h, the volume fraction of precipitates reached a peak value.The results of the corrosion test showed that a high corrosion resisting of the second phase precipitates was beneficial to improving the strength and hardness. Solution treatment at 445°C temperature for 12 h destroied the consecutiveness of β-Mg17Al12 phases.

Abstract: The oxidation kinetic curves of four kinds of austenitic stainless steel at 700°C was measured by weighting method. It is showed that the oxidation curves of those austenitic stainless steels follow the parabolic law. The mass gain of 800Al steel. is the least of all. The surfacemorphology and structure of the oxide scale were studied by scanning electron microscopy and X-ray diffraction methods. It is found that adense oxide scale formed at 700°C in all four austenitic stainless steels. In austenitic stainless steel with high Mn content, scales are mainly composed of Mn₂O₃ and the spinel MnFe₂O₄. Scales of austenitic stainless steel with high Cr content but without element Al are composed by Cr₂O₃ and the small amount of spinel FeCr₂O₄ . Scales of austenitic stainless steel with element Al and Cr are composed of (Fe0.6Cr0.4)2O3 and Al oxide, showing the excellent oxidation resistance property.

Abstract: Microarc oxidation coating and microarc oxidation-fluorocarbon coating were prepared on the surface of AZ80 magnesium alloy profiles. The phase structure, surface morphology and corrosion resistance of the coatings were investigated using SEM, XRD, copper sulfate spot test and polarization curve test. The main phase compositions of the microarc oxidation coatings were MgO, Mg₂SiO₄, MgSiO₃, MgF₂ and MgAl₂O₄. With increasing pulse voltage, the oxidation coating became thicker and the microstructure of the coating surface became compact; therefore the coating corrosion resistance was improved. The oxidation coating with pulse voltage of microarc oxidation controlled between 300-438V obtained the best corrosion resistance. The corrosion current density of magnesium alloy reduced 1-3 orders of magnitude after microarc oxidation treatment with increasing pulse voltage, and the corrosion resistance of microarc oxidation-fluorocarbon coating is desirable.

Abstract: When teeming rare earth treated steels the nozzle blockage occurred so frequently that seriously interferes the application of RE in steels. In this study we tried to investigate the relationship between the wettablility of 16MnRE steel and nozzle materials. The results showed that the weakest wettability of steel liquid was observed on fused silica among the six nozzle materials. Next came zircon and high-alumina nozzle. It has no obvious difference between the 16MnRE steels when final deoxidized containing and not containing Al addition. The wettability of 10Ti steel was weaker than 16MnRE steels on zircon nozzle. The clay nozzle was corroded by the precipitate from steel liquid.

Abstract: In order to study the performance on silicone rubber elastomer in small-size flexible joint at different temperatures, a series tests for two miniature flexible joints (joint-SR1 and joint-SR2) with the same structure and different formula of silicon rubber elastomer (phenyl silicon rubber and dimethyl silicon rubber) were conducted. Axial compressive stiffness and bending stiffness at various temperatures (-60 °C~20 °C) and vessel pressures (1MPa~8MPa) were studied. Results show that the axial compressive stiffness and bending stiffness of joint-SR1 remain stable throughout the temperature range of-60 °C~20 °C, while those remain stable throughout the temperature range of-40 °C~20 °C and become to be infinite at-50 °C due to the elastic failure of elastomer material for the joint-SR2. Analysis indicates that the reason that elastomer of joint-SR2 lost elasticity at-50 °C is not glass-transition but crystallization. The phenomenon of elastic failure did not appear throughout the temperature range-60 °C~20 °C for the joint-SR1 elastomer is due to the existence of phenyl side-group substitute. The modified chain content of silicone rubber not only affects the process of crystallization inhibition but also the crystallization rate. The rubber with phenyl or other bulky side-group could destroy the crystal of silicone rubber at low temperatures, which is beneficial to be applied in small-size flexible joint.

Abstract: Wood is ecological sustainable to be used as construction material.It plays an important role for green-building, reasonable resource utilization and environmental protection. Meanwhile, the wooden building has a special significance to China.Wood implicates the traditional Chinese living style and cultural essence. This article analyzed the advantage and feasibility of using wood as a construction material.Besides,it has made a detailed analysis in the application of wooden building materials in contemporary architecture. Furthermore, it has also done a case study to reveal the salient energy-saving effort of wood and eventually discussed the application prospect in China. Through all these studies, with processing and used by the modern technology, energy conservation and environmental protection characteristics, wood was established to be an important factor of contemporary architecture, and continues to promote the development of contemporary architectural culture.

Abstract: Using the radio frequency magnetron sputtering that directly bombardment A1N target under different sputtering-power and total pressure to deposit the A1N thin films. The crystal structure, composition, surface and refractive index of the thin films were studied by XRD, SEM, AFM and elliptical polarization instrument. The results show that the surface and refractive of the thin films strongly depends on the sputtering-power and total pressure,the good uniformity and smoothness is found at 225 W, Ar flow ratio 5.0 L_Ar/sccm, substrate temperature 100°Cand 1.2 Pa. All film thickness are from 60 to 80nm, and the highest N/Al mole ratio reach to 0.83.The crystal structure of the as-deposited thin-films is amorphous，then it transforms from blende structure to wurtzite structure as the rapid thermal annealing(RTA) temperature changes from 600 to 1200°C. The refractive index also increases with the RTA temperature it is increasing significantly from 800 to 1000°C. When the Annealing temperature at 1000°C, we get the best uniformity and smoothness of the surface of the film.