Advanced Materials Research Vols. 941-944

Abstract: Process of solution treatment of 2024 aluminum alloy was done by hardness test and microanalysis in this paper. The effects of different solution treatment temperature on the microstructure and mechanical properties of 2024 aluminum alloy were studied and the influence of overburning on the microstructure and mechanical properties of 2024 aluminum alloy were also analyzed. The experimental results show that overburning occurs while 2024 aluminum alloy is heated over 490°C×50min . The hardness tests and microstructure analysis results show that the hardness decreased, grain boundary becomes trigemanal and compounded –melting structure (burnt structure) appeared when overburning occuring for this alloy .

Abstract: Effects of niobium element adding method and addition content on the microstructure, thermal conductivity and melting point of Cu-Ni-Nb alloys prepared by vacuum non-consumable arc-melting were studied. We found that it is difficult to dissolve high melting point element Nb into Cu-Ni alloy by one-step smelting. However, Nb can be dissolved into Cu-Ni alloy in style of Nb-Ni master alloy by two-steps smelting. New phases Ni₃Nb and Ni₈Nb generate in matrix of Cu-Ni alloy. In addition, the thermal conductivity coefficient of Cu-Ni-Nb alloy increases as increasing the content of Nb, while melting point of that alloy decreases as increasing the content of Nb. Moreover, the thermal conductivity coefficient of Cu-20Ni-3Nb alloy is 43.23W/m•k, while melting point of that alloy is 1146°C. That meets the requirement of pure copper casting process.

Abstract: To solve the problem of alumina dissolution in perforated anode technology, dissolution behavior of alumina has been studied in the laboratory by simulating electrolyte parameters of the factory which has adopted the technology. The results show that alumina saturated solubility is 3.991% for system at 940°C. The relationship between dissolution rate and concentration of alumina does not have regular change when alumina concentration is less than about 1%. When the concentration is greater than about 1%, the dissolution rate declines with the increasing concentration of alumina. Combined with the production, the suggestions which can improve energy-saving effect are proposed as follows: the particle size and the concentration of alumina in the electrolyte should be controlled in the range of 44μm to 100μm and 1.5% to 3% respectively; the time interval of point loading and the alumina supply every time can be cut down properly and alumina can be preheated.

Abstract: The jewelry making has been traditionally considered handcrafted and hinged on the ability of goldsmiths to create components and assemblies. In recent years, however, a profound transformation has begun, driven by the global markets requiring robust engineering approaches to the analysis of new materials and of product/process optimization. Moreover, gold and silver were conventionally associated to the jewelry production, but the use of materials other than precious metals (such as steels, titanium alloys, woods and ceramics) is nowadays a standard for many companies. In this context, the research activities presented and described in this paper focus on the performance evaluation of a Zirconium alloy, in terms of material properties and machinability, for the application in the jewelry industry. Perspiration, salt spray and abrasion tests provided results comparable or even superior to those typical of a Ti-6Al-4V alloy, especially in case a Zirconia layer is induced on the Zirconium alloy through a properly designed oxidizing treatment. Machinability can be performed with conventional tools and equipment, and the production route of jewel prototypes is detailed.

Abstract: Hot Deformation behaviors and microstructural evolution of Al-Zn-Mg-Cu alloy with as-homogenized, as-forged and as-over-aged starting structures were studied at temperatures in the range of 300-420°C, strain rates in the range of 0.01-1s-1, and reductions in the range of 20%-80% by high-temperature compression tests. The flow stresses increase with increasing strain rate or decreasing temperature, which can be described by a hyperbolic-sine equation with the deformation activation energies of 246.35KJ/mol, 188.87KJ/mol and 178.25KJ/mol for the homogenized, the forged and the over-aged samples respectively. At the same deformation condition, the flow stress of the homogenized samples is greater than that of the forged and over-aged samples. For the homogenized samples, dendritic coarse grains elongated along the deformation direction, and interdendritic boundaries within coarse grains disappeared gradually due to diffusion at higher temperatures. When deformation is heavy, microstructures became into homogenous and geometric recrystallization occurs and new small grains appear within the severe elongated grains. For the forged samples, higher temperatures promote dynamic recrystallization. Recrystallized new small grains were developed along prior grain boundaries at large strains. For the over-aged samples, prior grains elongated along the deformation direction, and there is not much more dynamic recrystallized grains observed.

Abstract: Foam aluminum is a novel porous functional material. There are many methods for preparation of foam aluminum, wherein an infiltration casting method in the liquid phase method can be selected for the preparation. In the forming of a pore structure of the foam aluminum, infiltration depth and pore uniformity are mainly influenced by technological parameters including particle size and preheating temperature of particles and a mold, molten aluminum casting temperature and vacuum degree.

Abstract: Effect of Indium addition on the precipitation kinetics of Al8Si0.4Mg alloy has been investigated by differential scanning calorimetry (DSC) analysis. The activation energy analysis results show that the β′ precipitation activation energy is 85 kJ mol^-1 and 86 kJ mol^-1 for the base alloy and Indium containing alloy respectively. The β′ precipitation mechanism parameter n analysis results show that β′ precipitates in two-dimensional and the growth mechanism of β′ precipitates is unaffected by Indium addition. The nucleation density dependent parameter k for Indium containing alloy is 2.45 times of the base alloy which suggests that Indium addition accelerates the nucleation density of β′ phases.

Abstract: The effect of MgO on phase composition, alumina leaching properties and the self-disintegrating rate of calcium aluminate slag were investigated by X-ray diffraction and another analysis method. And a feasible method is proposed to eliminate the negative effects of MgO. The results shows that: the phase of 2CaO·SiO₂(C₂S)、20CaO·13Al₂O₃·3MgO·3SiO₂(Q phase) and 12CaO·7Al₂O₃(C₁₂A₇) are formed when there is MgO in slag with the C/A=1.4 and A/S=1.3. The content of Q phase increase and the leaching rate of slag reduce with increasing the temperature and the content of MgO. MgO would reduce self-disintegrating rate of slag. CaSO₄·2H₂O can improve the self-disintegrating the leaching properties of slag by promoting the synthesis of C₁₂A₇ and inhibit the synthesis of Q phase.

Abstract: Compression tests of Mg-13Al-3Ca-3Zn-1Nd-0.2Mn Magnesium alloy as-extruded had been performed in the compression temperature range from 200°C to 400°C and the strain rate range from 0.001 s−1 to 10 s−1 and the flow stress data obtained from the tests were used to develop the power dissipation map, instability map and processing map. The most unsuitable zones in the power dissipation map including 200°C - 315°C and 0.01s^-1 - 0.1s-1 zone, 315°C - 400°C and 0.001s^-1 - 0.01s^-1 zone and 340°C - 360°C and 0.32 s^-1 - 0.56 s^-1 zone. The most unsuitable zones in the instability map are 310°C - 400°C, 0.001s^-1 to 0.56 s^-1 zone and 330°C - 400°C, 1s^-1 to 10 s^-1 zone. The most suitable temperature range is 330°C - 400°C and most optimal strain rate ranges are 1 s^-1 - 10 s^-1 and 0.001s^-1 - 0.56 s^-1.