Advanced Materials Research Vols. 1120-1121

Abstract: The influence of different flame of gas welding on corrosion behavior of the carbon steel’s heat affected zone in seawater were studied by the weight-loss method, electroanalytical chemistry method and surface and microstructure observation. The result indicate that when gas welding the carbon steel, the corrosion rate of the heat affected zone under the influence of mild carbonizing flame is 0.1252[g／(m²•h)], in contrast, the corrosion rate of that under the influence of neutral flame is 0.1025[g／(m²•h)]; the order of corrosion current shows as follows: I_{mild carbonizing flame}>I_{neutral flame}>I_{base metal}; the order of measured corrosion potential as follows: E_{base metal}>E_{neutral flame}>E_{mild carbonizing flame}. Compared with the base metal, the heat effected zone are more likely to corrosion, corrosion resistance of the sample under mild carbon flame are the worse.

Abstract: Study the property and resistivity of Low-pressure semi-solid die casting ( LPSSDC) aluminum wheel hub after heat treatment. The Brinell hardness has reached more than 100HB in all position. Tensile properties at inner rim and outer rim are both reached 280MPa. The result of resistance analysis on LPSSDC aluminum wheel hub is below. The resistivity of the material is only influenced by the supersaturated solid solution (SSSS), GP zone, metastable phase β 'and stable phase β (Mg₂Si). The resistivity has a decline during aging 0-0.5h and 0.75-8h, and an increasing during 0.5-0.75h. The resistivity remains stably when the decomposition of the solid solution achieved a dynamic balance after 8h aging time.

Abstract: The Nickel Titanium (NiTi) alloy is a shape memory alloy. It presents two distinct properties: shape memory effect (martensite phase at room temperature) and the pseudoelasticity (austenite phase at room temperature). These materials are frequently used in industries like engineering, dentistry, medicine and aeronautics, and for certain applications it is important to know the wear behavior of these alloys.Thus, this study aims to evaluate the micro-abrasive wear behavior of pseudoelastic NiTi alloys at the as received and aged conditions, and compare with results obtained for NiTi alloy with shape memory effect. The aging heat treatment was performed at temperatures of 350, 450, 500 and 600 °C with an isotherm of 30 minutes and subsequent quenching in water. The wear tests were carried out in a free ball machine. After wear testing was observed that the wear coefficient obtained were lower for all treatment temperatures when compared to pseudoelastic NiTi alloy as received, reducing wear by 30 % in case of treatment at 350 °C. The alloy with shape memory effect showed good wear behavior, with a wear coefficient about 14 % less than the untreated pseudoelastic NiTi alloy.

Abstract: Magnesium alloy as a green material in the 21st century, because of its excellent physical and mechanical properties of metallic materials as an ideal in the automotive industry, electronic industry and aviation, aerospace and other industries^[1]. However, poor corrosion resistance of magnesium alloys become an important issue hinder application of magnesium alloys^[2]. So magnesium alloy corrosion problems and the current status of research paper reviews several magnesium alloy protection methods at home and abroad, and also highlighted with our latest laser shock (LSP) study of AZ91 magnesium alloy at high strain rates of corrosion resistance results.

Abstract: This study investigated the fatigue crack propagation of Al–Mg–Mn–Zr alloys with erbium. The research found that in this alloy the crack propagation path prefers to extend along the grain boundary. If there are too many second phases or impurities in the gain boundary, the crack propagation will be influenced. The dispersed Al₃(Er, Zr) precipitate in the alloy can act as a core of heterogeneous nucleation to attract Mg, Zn and Al element, and reduce the large brittle Al₃Mg₂ second phase appear on the grain boundary, so the fatigue crack propagation rate can be slow down. In addition, these Al₃(Er, Zr) precipitate can pin the dislocation in the alloy to reduce stress concentration at the grain boundary, so it also has some positive effect to the fatigue crack propagation.

Abstract: The electricity consuming of aluminium electrolysis cell is affected by the voltage drop of anode steel claws during the aluminium electrolysis course. The resistivity of anode steel claws is affected by the temperature. In the present study, the thermal field distribution of anode steel claws was studied by finite element analysis. The results show that the thermal energy of anode steel claws come from anode carbon blocks and environment. The temperature of steel claws less than 1/3 height is affected by anode carbon blocks, and the other part is affected by surrounding temperature. According the results, the principle of the new anode steel claw design is proposed.

Abstract: As one of the key techniques for manufacturing three-dimensional metal microstructure, micro-electroforming processing technology plays an important role in MEMS. Mechanical properties of micro-electroforming Ni have become a new research hotspot. This paper gives a brief overview of micro-electroforming Ni material’s mechanical properties. Due to the complexity and lack of standardization during micro-electroforming process, mechanical properties are found to be dependent on micro-electroforming process parameters and conditions. It is essential to reveal the essence of mechanical properties from microcosmic aspect. This paper briefly summarizes observation tools of microstructure and reviews the relationship of mechanical properties and microstructure. This work lays theoretical foundation for dynamic analysis and calculation of micro-electroforming Ni devices.

Abstract: The compatibility of molten Mg-25Al-15Zn-14Cu alloy with several candidate vessel shell materials such as 304 stainless steel, 201 stainless steel for phase-transformation thermal storage facility were evaluated by means of immersion corrosion test at 500°C for 1000 h. The microstructure, element distribution and surface corrosion layer structure and phase composition of the cross section of corrosion samples were analyzed by using optical microscope (OM), X-ray diffraction (XRD) and electron microprobe analysis (EPMA). The results show that two kinds of stainless steel have good compatibility in the molten Mg-25Al-15Zn-14Cu alloy. The thickness of the erosion layer is less than 0.1mm. The corrosion interface of corrosive material in the molten Mg-25Al-15Zn-14Cu alloy can be divided into the base layer, the diffusion layer, the corrosion layer, segregation layer (C, Cr, Ni), linked coating layer.

Abstract: With the help of optical microstructure(OM), X-ray diffraction(XRD) and differential scanning calorimetry(DSC), the microstructure and storage heat performance of Mg-based phase change thermal storage alloys were investigated.The results show that the microstructure of Mg-25Al-15Zn-xCu (x=0, 2%, 8% and 14%, respectivly) alloys are mainly composed of primary crystal α (Mg) solid solution matrix, β-Mg₁₇Al₁₂, CuZn, MgAl₂Cu and Mg₃₂(Al,Zn)₄₉ phases. The phase transition temperature of Mg-25Al-15Zn and Mg-25Al-15Zn-8Cu alloys ​​are 412.1 °C and 405.9 °C respectively; and phase change latent heat values of that were 175.4 J/g and 209.3 J/g. The addition of Cu led to the formation of new phase, reducing the phase transition temperature and increasing the value of phase change latent heat.

Abstract: This study investigated the mechanical properties and microstructures of Er-containing Al–Mg alloys. The research found that the H114-T sheet of Er-containing Al–Mg alloys showed a relative good comprehensive performance in mechanical properties. With the special rolling and heat treatment process, this H114-T sheet showed different morphology of microstructures with the other sheets in Er-containing Al–Mg alloys. Grains in H114-T sheet performed irregular shape polygon, a number of subgrains appeared in grains, the amount of dislocations in grains decreased. H114-T sheet possessed a lot of Copper texture, this may be one of important factors influenced the mechanical properties.