Advanced Materials Research Vols. 887-888

Abstract: The flow stress behavior of the 7075-T6 aluminum alloy was studied through single-pass compression experiment by using MMS-300 simulator within temperature range of 300-450°C and strain rate range of 0.01-40s^-1. Then a simulation of compression was carried out and the influence of deformation velocity on load and deformation heating was investigated according to the relationship between stress and strain. The results show that dynamic recrystallization occurs in hot compression of 7075-T6 alloy and the stress-strain curves are presented as wave. Furthermore, the flow stress curves have the same wave period and the fluctuation range increases with an increase of strain rate and a decrease of strain. Increasing of deformation velocity results in higher critical strain but the value decreases when the deformation velocity is much higher. The temperature rise increases with the increase of deformation velocity and decrease of deformation temperature. The maximum of temperature rise is more than about 30°C, so that the deformation heating is significant.

Abstract: Between aircraft bearings lugs, plates fracture appeared. The failure mode and cause were analyzed by macro and micro observation, EDS analysis, metallographic examination and hardness testing. The results showed that two bearings’ failure were stress corrosion cracking. Bearings’ failure were related with abnormal force state, material cast loose exceeding the allowed limited values played a catalytic role to crack propagation. It is suggested that bearings material surface protection should be strengthened to improve corrosion resistance, bearings design should be optimized to avoid abnormal tensile stress, and material casting process should be improved to reduce cast loose.

Abstract: An experimental investigation on the solubility of Zr in Cu-Sn alloy was conducted in a resistance furnace. The solubility of Zr in Cu-Sn alloy was determined by investigating the influence of different conditions such as the ratio of Cu-Sn alloy and temperature. The solubility of Zr in Cu-Sn alloy changes with the proportion of Cu and Sn, and it increases with the increasing of Cu content. The experimental temperature has a significant effect on the solubility of Zr in Cu-Sn alloy. The maximum solubility of Zr in Cu-Sn alloy is 6.2 mass % at 900 °C with the mass ratio of Cu : Sn = 8:2.

Abstract: Grain structure and precipitates in squeeze casting Al-Li-Mg-Zr alloy for aircraft industry were investigated in heat treated condition, using X-ray diffraction, optical microscopy and transmission electron microscopy. An ultra fine grained structure in sub-micrometer size was obtained, having fine nanograins in it with polycrystalline diffraction rings that are different from the single-crystal patterns in the matrix. Ultra fine grain areas are generally located on the grain boundaries and sub-grain boundaries. In addition, TEM observations indicates the presence of lenticular δ' (Al₃Li) phases that symmetrical distributed around the GP zones. The alloy also contains spherical β' (Al₃Zr) dispersoids, and S₁ (Al₂MgLi) phases.

Abstract: Dynamic of phase transformation has been investigated through the measurement and analysis of relationship between electronic conductivity and the volume fraction of precipitates in the aging process of Cu-Cr-Zr alloy. According to above experiment, the Avrami empirical equation and electronic conductivity equation can be respectively confirmed at different aging temperature. S-curve of the dynamic for phase transformation at different temperature and C-curve of isothermal transformation for the Cu-Cr-Zr alloy are obtained.

Abstract: This paper compares and discuses coating cracks on the deformed part of galvanizes dual phase steel after standard 0t bend test. And it is further founded that cracks concentrate on areas where the ζ-FeZn₁₃ phase is dense. Further investigation figures out relationships between cracks generation and ζ-FeZn₁₃ phase.

Abstract: Cube texture formation of Cu-33 at.%Ni alloy substartes and CeO₂ buffer layer prepared by chemical solution deposition on the textured substrate were investigated by electron back scattered diffraction (EBSD) and XRD technics systematically. The results shown that a strong cube textured Cu-33at.%Ni alloy substrate with the cube texture fraction of 99.8 % (< 10°) was obtained after annealing at 1000°C for 1 h. The full width half maximum (FWHM) values for the X-ray (111) phi-scan and (002) omega-scan in this substrate were 7.31° and 5.51°, respectively. Furthermore, the cube texture fraction of epitaxially grown CeO₂ buffer layer was 95 % (< 10°), and the FWHM values of phi-scan and omega-scan being 6.98° and 5.92°, respectively.

Abstract: The heat treatment process of a kind of hypereutectic aluminum silicon alloy which is suitable for semi-solid forming and the change of microstructure and performance during the process of heat treatment had been studied in this paper. In order to guide the heat treatment process, the phase diagram of the alloy had been calculated by the software of Thermo-Calc, and the theoretical solid and liquid line had been gotten. Twelve kinds of heat treatment process had been selected in this study. Finally the best process which the solution temperature is 495°C for 2h and aging temperature is 160°C for 8h had been gotten.

Abstract: The corrosion behavior of Incoloy 800 as the receiver tube materials in a solar tower field exposed to a mixed molten nitrate salts (KNO₃: 40wt.%, NaNO₃: 60wt%) at 560°C, has been investigated by several methods. After Incoloy 800 specimens were immersed respectively in molten salts at 560°C for different times (5h, 10h, 20h, 30h, 40h, 60h, and 80h), the weight-loss of specimens were test, the morphology of oxide films on the Incoloy 800 specimens were observed by Optical microscope (OM) and Scanning electron microscopy (SEM), the phase composition of the oxide film were investigated by X-ray diffraction (XRD) and Energy dispersive spectrometer (EDS). The experimental results revealed that the corrosion kinetics of the tested alloy agreed with the parabolic law at 560°C, and the corrosion rate is 91.5μm/year. The analysis of the phase composition shows the oxide films had a duplex layer structure with Fe₂O₃ in the outer layer, andγ-(Fe,Ni) and Cr₂O₃ in the inner layer.

Abstract: Cu-15Ni-10Mn alloy as-cast, which smelted at atmosphere, has a typical dendrite structure in Ni segregation characteristics. The content of Ni is higher on dendrite arms spacing than on the dendrite arms, but the content of Mn is less than on the trunk. Due to the Mn oxides easily, the processing performance of alloy as-cast cant meet the requirement of metalworking. The gas content of ingots can be reduced by adding a small amount of zinc during smelting, and the metalworking features can be improved by adding trace Ti that will refine the arms of alloy. The research results show that the grains of Cu-15Ni-10Mn alloy as-cast can be refined by tiny amount of Ti. The grain size decreases with the increase of the content of Ti, the branches size of alloy adding 0.2% Ti is about 30μm that is only 49.4% the size of the alloy without Ti. Titanium, copper and Nickel can form compounds of CuNi2Ti. The hardness peak of alloy with 0.2%Co is 114Hv that is 8% higher than the alloy without Ti. The electrical conductivity of Cu-15Ni-10Mn alloy as-cast waves not clearly.