Applied Mechanics and Materials Vols. 496-500

Abstract: Semi-solid 2024 Al alloys with strontium (Sr) addition of 0.15 wt% and 0.3 wt% were prepared by Gas Induced Semi-Solid (GISS) process. Effect of Sr addition on the microstructure and mechanical properties of the semi-solid 2024 alloy was investigated. It was found that the tensile strength and % elongation of the T6 heat treated alloy with the Sr addition were higher than those without Sr addition owing to the reduction of Mg₂Si phase formation. The semi-solid 2024 Al alloy with 0.15%Sr addition obtained the average highest tensile strength of 382 MPa and elongation of 6.45%.

Abstract: Corrosion behaviors of ultra high strength steel 22MnB5 and its weld were studied based on electrochemical method in the present work. Electrochemical measurements such as Tafel polarization curve and electrochemical impedance spectroscopy were performed to investigate the corrosion mechanisms of 22MnB5 steel and its weld. The testing results indicated the weld metal possessed less corrosion resistance than the base metal, and the main reason for this phenomenon is the microstructure variation of the weld metal.

Abstract: The problems of the tooth root bending stress increase,distortion, the life of the gear reduction and other issues existing in the gear heat treatment process, In order to solve these problems, functionally gradient material (FGM) was used on gear working surface. the analysis of heat treated gear performance and common gear performance comparison analysis has maded; A functionally gradient material cylindrical involute gear model and a common cylindrical involute gear model were created, Then finite element calculation of bending stress and analysis of the two models has maded. The FGM gear have better performance on the root bending stress and the hardness of the working surface, and also can avoid disadvantages about distortion and uniform carburized layer which might happened in heat treatment process. The experimental results show that FGM can be used on gear.

Abstract: (SiC_p+Al₂O_3f)/7075Al composites as potential friction materials were prepared in this paper by pressure infiltration and some related properties were compared with traditional friction materials. The addition of Al₂O₃ fiber to SiC preform could contribute to enhance compressive strength of the preform as well as tensile strength of the composites. The tensile strength of as-fabricated composites with 35vol%SiC_p + 15vol% Al₂O_3f could reach 402MPa and the friction coefficient is about 0.4 and the thermal conductivity is higher than 120W/mK. Compared with traditional materials such as nodular cast iron, the composites exhibit better comprehensive properties and are suitable as brake materials for automobile.

Abstract: Eu-doped ZnO (ZnO:Eu) hollow nanofibers were fabricated by sputtering using electrospun PVP nanofibers as templates. The morphologies, crystal configuration, bonding structures and optical properties of the ZnO:Eu hollow nanofibers were characterized, respectively. Raman results indicate that there are many oxygen vacancies and/or interstitial zinc in ZnO:Eu hollow nanofibers. Effect of Eu-doping on vibrating modes of ZnO is attributed to the change of defects and impurities due to incorporation of europium. The high intensity ultraviolet emission and red luminescence of the ZnO:Eu hollow nanofibers are observed due to the random lasing of near-band-gap emission of ZnO and an f-f transition of the Eu³⁺ ions, respectively.

Abstract: Abstract: this paper describes the main characteristics of bottom blowing argon, and by comparing forging adopting the mode of bottom blowing argon process of forging with not using the technology of forging the same time and the same kind of shape of ingot production the same in the forging crack, the results of the ultrasonic flaw detection, grain size, mechanical properties, gas content in liquid steel, the influence of the mold bottom blowing argon through the comparative analysis on the influence of the inclusions, the method of die bottom blowing argon can improve the quality of steel, It is worth promoting. And the principium of die bottom blowing argon is discussed.

Abstract: CuAlO₂ microcrystallites were synthesized by Sol-gel method at 1200°C with Cu (CH₃COO)₂·H₂O, Al (NO₃)₃·9H₂O and ethylene glycol as raw materials. The phase composition,morphology,and optical properties of CuAlO₂ microcrystallites were chatacterized by X-ray diffraction, Scanning electron microscope,Photoluminescence and UV-visible spectroscopy respectively. The results of XRD show that CuAlO₂ with delafossite crystal structure is obtained. The defect emission were observed through PL spectrum test. It can be concluded that Cu-vacancy may be the possible reason of the observed activated p-type conductivity of CuAlO₂. Can be found three characterized peak (λ₁=290nm, λ₂=410nm, λ₃=430 nm) on the spectra.

Abstract: The purpose of this study was to investigate the tensile properties and plasticity of semi-solid 6061 Al alloy at room and elevated temperatures. The semi-solid 6061 alloy was produced by the Gas Induced Semi-Solid (GISS) technique followed by squeeze casting process. The conventional liquid squeeze cast (CLC) 6061 alloy was also fabricated for comparison. The tensile tests were performed at temperature of 25 °C, 100 °C and 175 °C. The experimental results showed that the UTS, 0.2% yield strength and % elongation at break of the SSM alloy are higher than those of the CLC one at all temperatures. Based on the simple flow law, σt=Kεtn , the strain hardening exponent n and the strength coefficient K of the SSM alloy are lower than those of the CLC. The SSM alloy demonstrates more plasticity than the CLC. The results may be attributed to the more globular structure of the SSM alloy.

Abstract: In this research, the semi-solid state joining of SSM A356 aluminum alloy was investigated. The butt-joint of SSM A356 was heated by an induction heating coil to create a localized semisolid pool. Then a stirrer was applied into the joint seam in order to mix the weld metal. The accurate controlling of temperature during joining was measured. The effects of stirring rate on physical, macrostructure, microstructure and mechanical properties were studied. Experimental results showed that increase in stirring rates, the surface of the joint was smooth. The weld metal consisted of the globular microstructure and also voids. The density of weld metal zone increased by an appropriate stirring. The best tensile strength was achieved with 1750 rpm, 70 mm/min for 103.4 MPa.

Abstract: Progresses of novel photocatalysis materials and technologies were introduced in this paper. Efficacy-strengthening technologies of TiO₂ photocatalysts include grain-refining and preparation of porous materials, improvement of visible light-responsive ability. Moreover, researchers are developing novel photocatalysts materials and equipments with high efficacy, novel photocatalysis materials include small gap materials, new-serie photocatalysis materials, some natural compounds, broad-spectrum photocatalysts and broad-energy and energy-sensitive catalysts, etc, in addition, high-efficacy controllable high-power environment-cleaning equipments such as high-voltage negative-ion generator and plasma generator have been developed to dispose heavy pollutants in industrial fields.