Superplastic Improvement of Aluminum 7475-T4 Industrial Sheets Using a Heat Treatment

The mechanisms of deformation and failure of age-hardenable aluminum alloys due to ultrasonic cavitation have been investigated. The results indicate that the mode and rate of erosion depend on both composition and heat treatment: increasing the hardness and strength by aging or alloying produces an increase in erosion resistance togetner with a change in failure mode. Alloys of low solute content erode in a manner similar to that of pure FCC metals namely by uniform ductile rupture across the surface. In the samples of 2 to 4.5 pct alloy content, however, material is lost preferentially from apparently random, isolated regions, leaving behind striated, flat-bottomed pits. The fracture surface of these pits resembles those of fatigue failures in aluminum alloys. These pits expand laterally to macroscopic proportions on continued caviation exposure without suffering any changes in their topographical features. Alloys of 9 to 10 pct solute content develop similar striated pits but on a microscopic scale. These different erosion mechanisms are discussed in terms of the microstructure of the alloys and their ability to absorb and attenuate the incident cavitation energy.

The mechanism of thermally induced elongation in poly(ethylene terephthalate) fiber spun at 3500 m min−1 has been examined. This partially oriented fiber has a crystalline content of about 25% and a high degree of orientation. The effect of time and tension during heat treatment was examined, and it was found that yarns that were allowed to relax during an initial brief heat treatment at 130°C subsequently elongated by up to 5% during a long heat treatment at the same temperature. Yarns that were not allowed to relax during the brief heat treatment did not elongate on subsequent heating. The morphological and mechanical changes associated with these processes have been studied using differential scanning calorimetry, X-ray diffraction (XRD), birefringence measurement, microscopy, and tensile testing. A large increase in crystallinity was observed during the brief heat treatment, but a much smaller increase took place during the long heat treatment. XRD indicated that substantial crystal reorganization occurred during both heat treatments, but c-axis growth was most significant in those materials that elongated during long heat treatment. It is proposed that it is this c-axis growth, in conjunction with conversion of disordered amorphous material into oriented crystalline material, that is responsible for the observed elongation. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 989–995, 1997

The rare–earth giant magnetostrictive materials are one kind of the most important functional materials now. The rare–earth giant magnetostrictive materials of TbFe2 and Tb0.27Dy0.73Fe1.95(R–Fe) alloys were firstly used in sonar system in military. Now, the applications of these two alloys have been developed widely in both industry and civil fields, such as magnetomechanical transducers, actuators, adaptive vibration control systems, and so on. The TbFe2 and Tb0.27Dy0.73Fe1.95 alloys both have the C15–type cubic Laves phase structure, which has strong magnetic anisotropy. This causes that the alloys exhibit different magnetostrictive properties along different crystal orientations. So, the preparation of high orientation degree magnetostrictive materials has a great of importance. In this work, it is predicted that the magnetostricive property of these two alloys can be enhanced with high magnetic field during heat treatment around their Curie and eutectic points. Therefore, a high magnetic field up to 11.5 T was imposed on these two kinds of R–Fe alloys during heat treatment at different temperatures in the experiments. Then the effects of high magnetic field on the crystal orientation, morphology and magnetostriction were analyzed in detail by XRD, metallographic microscope, and static resistance strain gauge. Also, the relationship between structure * K`W}h=dL+ 51006020, 51174056, KPe==osy3H3L+ 2011CB612206 'Jv T= }o9L+ N120409001, N120509001 ^W X: ℄A : 2013–05–28, X` ℄A : 2013–07–24 m8Nb : , ,, 1982 2m, zm DOI: 10.3724/SP.J.1037.2013.00289 9 AE` : KH0[A u TbFe2 ) Tb0.27Dy0.73Fe1.95 ,fl TO / [!)HEj _0^ K 1149 and property is discussed. The results showed that high magnetic field didn’t change the orientation of the R–Fe alloys, but the orientation degree had a great improvement after heat treatment. The phase composition of the two alloys had no change. However, the heat treatment with a magnetic field up to 11.5 T distinctly reduced the rare–earth phase of TbFe2 and obviously increased the magnetic phase. In addition, the magnetostrictive property of TbFe2 alloy increased after the heat treatment with high magnetic field. But for Tb0.27Dy0.73Fe1.95 alloy, the magnetostriction was not obviously enhanced. The reason for the improvement of the magnetostriction is that the Zeeman energy caused by high magnetic field increased the total Gibbs free energy of the system, which made the random orientation in crystals orient along the 〈113〉 direction, and enhanced the magnetostriction of the R–Fe alloys.

Microenvironment engineering for enhancing catalytic active sites for the CO oxidation reaction.

Additive friction stir deposition of multi-layer aluminum-silicon carbide metal matrix composites

The paper investigates the process of "soft" mechanochemical synthesis of the CuO/ZnO/Al2O3 composite using copper/zinc hydroxocarbonates and aluminum oxide as feedstock. Using the methods of X-ray phase and synchronous thermal analysis, the patterns occurring at the stage of mechanochemical activation and further heat treatment have been studied. The effect of the mill's energy stress on the textural properties of the composite is shown. By the method of low-temperature adsorption-desorption of nitrogen, it was found that in the process of mechanochemical synthesis, the total specific surface of the samples changes slightly, while the nature of processing has a significant effect on such textural characteristics as pore size distribution, active surface and dispersion of copper. Using the thermoprogrammable reduction method, the temperature ranges of activation of the composite for its use as a catalyst were obtained. The positive effect of mechanical activation on the formation of the composite structure, which makes it possible to use it as the main component of the catalyst for the production of ammonia, hydrogen and methanol, is shown.

NH3 plasma synthesis of N-doped activated carbon supported Pd catalysts with high catalytic activity and stability for HCOOH dehydrogenation

. Production efficiency as well as the reduction of energy consumption and waste are the main drivers for the improvement of large-scale production in chemical industry. In addition, the demand for new processes – these days especially related to the chemical energy conversion as basis for the Energiewende – are additional triggers for innovation. Catalysis, well recognized by the public e.g. in form of the 3-way automobile catalyst, plays an important role for about 90% of all processes in chemical industry. The development of new and improved catalysts is a challenge for chemists – as is the search for new structural materials for mechanical engineers. Due to the often-necessary noble and thus expensive metals (e.g. palladium) in many catalysts, structural and chemical function have been developed separately in the two communities. Recent progress in catalytically active materials allows replacing expensive noble metals in selected catalytic processes by significant cheaper elements [1]. This offers the new perspective to combine structural and chemical functionality by innovative materials. Within this area, intermetallic compounds with their peculiar combination of crystal and electronic structure [2], represent an interesting class of materials to address this vision as will be shown in the contribution.

Oxidation of oat β-glucan in aqueous solutions during processing.

The present study investigates the effect of two heat treatments on the microstructure, the tensile and the fatigue properties of a powder metallurgy tool steel that has undergone two heat treatments: quenching and multiple tempering (conventional for powder metallurgy tool steel), and quenching and multiple tempering with an intermediate cryogenic step at −80 °C (new solution). The findings of the research indicated that the new heat treatment promotes the development of a homogeneous distribution of carbides in the martensitic matrix, with an increase of about 10% in tensile strength and about 7% in elongation to failure. This combination of exceptional strength with a high degree of toughness leads to an improvement in the fatigue behaviour of the steel, which exhibits a higher unnotched and notched fatigue strength (about 15% and 25% respectively) and a lower fatigue notch factor (about 15%) compared to conventionally heat-treated steel. These results highlight that the powder metallurgy tool steel, with the new heat treatment, could be a viable option for the production not only of tools and dies, but also for high-performance automotive components, including even those with complex geometries, such as camshafts or crankshafts.

The microstructural evolution of DD9 single crystal superalloy turbine blade was studied after heat treatment. In comparison to the as-cast microstructures where the sizes of the γ′ precipitates have an obvious difference between the dendritic core and interdendritic regions, the γ′ sizes of the heat-treated microstructures tend to be uniform and more cubic. And in the heat-treated microstructures, the γ′ sizes and the related size dispersion degrees of the dendritic cores are slightly increased, while those of the interdendritic regions are obviously decreased. After all, all the γ′ sizes follow the normal distribution law. With the raise of section thickness, the γ′ sizes tend to increase and the related size dispersion degrees are enhanced during the cooling process after heat treatment, and the γ-γ′ eutectics are dissolved, left little residual eutectics and pores.

Preparation of solution-grown lozenge-shaped poly(p-phenylene terephthalamide) single crystals and their structural stabilization by heat treatment

This article investigates the effect of the higher Fe content on the formation of brittle Fe-rich needle-like phases in heat-treated secondary AlSi7Mg0.6 cast alloy. These secondary-recycled alloys contain an increased amount of impurities due to remelting of scrap. The common unwanted impurity found in these alloys is Fe. Its higher content negatively affects the structure and mechanical properties. Fe has low solubility in Al-alloys thus forming unwanted intermetallic phases such as β-Al5FeSi. Fe cannot be removed in the foundry conditions, so its content is reduced to an acceptable limit. One of the possibilities to eliminate the negative effect of high Fe content on the structure and mechanical properties is heat treatment. Heat treatment influences the size and morphology of structural components, which leads to a finer structure and thus better mechanical properties. Therefore, this study is focused on the changes in structure depending on the Fe content influenced by heat treatment applied to the secondary AlSi7Mg0.6 alloy with higher Fe content and evaluation using a scanning electron microscope, including methods of EDX analysis, and methods of deep etching.

Comparison of AlSi7Mg0.6 alloy obtained by selective laser melting and investment casting processes: Microstructure and mechanical properties in as-built/as-cast and heat-treated conditions

The nanostructured ferritic alloy 14YWT is a promising candidate for in-core use in generation IV nuclear reactors, due to a dense dispersion of insoluble, ultrafine-scale Y-Ti-O nano-oxides, which provide a high degree of irradiation tolerance and thermal stability. This study investigates the effects of heat treatment on the workability of 14YWT, along with the effect of processing history on abnormal grain structures and radial microstructural uniformity. In this study, a 14YWT rod consolidated at 850 °C was heat treated in argon at 1100 °C, 1150 °C, 1200 °C, or 1250 °C for 1 or 8 hours and changes in mechanical properties and microstructure were examined using microhardness and electron backscattered diffraction (EBSD). Two distinct types of large abnormal grains were observed, each with unique processing origins, including one with high and the other with low strain energy. Consolidation via direct extrusion resulted in radial microstructural gradients, where the center of the rod was softer with larger grain sizes and lower strain energies. These gradients persisted and intensified throughout heat treatment. Based upon this work, the recommended heat treatment for increased workability with minimal microstructural change is 1150 °C for 1 hours.