The fatigue properties of pressure diecast zinc-aluminium based alloys

The fatigue behaviour of the cold chamber pressure-die-cast alloys: Mazak3, ZA8, ZA27, M3K, ZA8K, ZA27K, K1, K2 and K3 was investigated at temperature of 20°C. The alloys M3K, ZA8K and ZA27K were also examined at temperatures of 50 and 100°C. The ratio between fatigue strength and tensile strength was established at 20°C at 107 cycles. The fatigue life prediction of the alloys M3K, ZA8K and ZA27K was formulated at 20, 50 and 100°C. The prediction formulae were found to be reasonably accurate. All of the experimental alloys were heterogeneous and contained large but varying amounts of pores. These pores were a major contribution and dominated the alloys fatigue failure. Their effect, however, on tensile failure was negligible. The ZA27K possessed the highest tensile strength but the lowest fatigue strength. The relationship between the fracture topography and the microstructure was also determined by the use of a mixed signal of a secondary electron and a back-scattered electron on the SEM. The tensile strength of the experimental alloys was directly proportional to the aluminium content within the alloys. The effect of copper content was also investigated within the alloys K1, K2, ZA8K and K3 which contained 0%, 0.5%, 1.0% and 2.0% respectively. It was determined that the fatigue and tensile strengths improved with higher copper contents. Upon ageing the alloys Mazak3, ZA8 and ZA27 at an ambient temperature for 5 years, copper was also found to influence and maintain the metastable Zn-Al (αm) phase. The copper free Mazak3 upon ageing lost this metastable phase. The 1.0% copper ZA8 alloy had lost almost 50% of its metastable phase. Finally the 2.0% copper ZA27 had merely lost 10% of its metastable phase. The cph zinc contained a limited number of slip systems, therefore twinning deformation was unavoidable in both fatigue and tensile testing.

The creep properties of a series of zinc-rich zinc-aluminium alloys

The compressive creep behaviour of six sand cast zinc-rich alloys: No3 and No5, corresponding to BS 1004A and BS 1004B, respectively, alloy No2, ILZRO,.16 and two newer alloys ACuZinc5 and ACuZinc10 was investigated. The total creep contraction of the alloys was found to be well correlated using an empirical equation. On the basis of this equation, a parametrical relationship was derived which allowed the total creep contraction to be related to the applied stress, the temperature and the time of test, so that a quantitative assessment of compressive creep of the alloys could be made under different testing conditions. The primary creep and secondary creep rates were found for the alloys at different temperatures and stresses. Generally, the primary creep contraction was found to increase with copper content, whereas secondary creep rates decreased in the order No3, ACuZinc10, ACuZinc5 and No2. ILZRO.16 was tested only at the highest stress and two higher temperatures. The results showed that ILZRO.16 had higher creep resistance than all the other alloys. Thus, based on the above empirical equation, alloy No2 was found to have a substantially better total creep resistance than alloys No3 and No5, and slightly better than ACuZinc5 and ACuZinc10 for strains up to 1%. Both ACuZinc alloys had higher creep strength than commercial alloys No3 and No5. Alloy No5 had much higher creep resistance than alloy No3 under all conditions. The superior creep resistance of alloy No2 was considered to be due to the presence of small precipitates of -phase in the zinc matrix and a regular eutectic morphology. The stress exponents and activation energies for creep under different testing conditions were found to be consistent with some established creep-controlling mechanisms; i.e. dislocation climb for alloy No3, dislocation climb over second phase particles for alloys No5, No2, ACuZinc10, controlled by lattice diffusion in the zinc-rich phase. The lower creep resistance of alloy No3 was mainly due to the lower creep strength of copper-free primary particles having greater volume than eutectic in the microstructure. Alloys No5, ACuZinc5 and ACuZinc10 showed much better creep resistance than alloy No3, based on the precipitation-hardening due to the presence of small -phase precipitates. The primary dendrites in both ACuZinc alloys however were not of much benefit in improving the creep resistance of the alloys.

Efeito da moagem de alta energia na densificação e microestrutura do compósito AI2O3-Cu

The Cu-Al2O3 composite ceramic combines the phase of alumina, which is extremely hard and durable, yet very brittle, to metallic copper phase high ductility and high fracture toughness. These characteristics make this material a strong candidate for use as a cutting tool. Al2O3-Cu composite powders nanocrystalline and high homogeneity can be produced by high energy milling, as well as dense and better mechanical structures can be obtained by liquid phase sintering. This work investigates the effect of high-energy milling the dispersion phase Al2O3, Cu, and the influence of the content of Cu in the formation of Cu-Al2O3 composite particles. A planetary mill Pulverisatte 7 high energy was used to perform the experiments grinding. Al2O3 powder and Cu in the proportion of 5, 10 and 15% by weight of Cu were placed in a container for grinding with balls of hard metal and ethyl alcohol. A mass ratio of balls to powder of 1:5 was used. All powders were milled to 100 hours, and powder samples were collected after 2, 10, 20, 50 and 70 hours of grinding. Composite powders with compact cylindrical shape of 8 mm diameter were pressed and sintered in uniaxial matrix resistive furnace to 1200, 1300 to 1350 °C for 60 minutes under an atmosphere of argon and hydrogen. The heating rate used was 10°C/min. The powders and structures of the sintered bodies were characterized by XRD, SEM and EDS. Analysis TG, DSC and particle size were also used to characterize the milled powders, as well as dilatometry was used to observe the contraction of the sintered bodies. The density of the green and sintered bodies was measured using the geometric method (mass / volume). Vickers microhardness with a load of 500 g for 10 s were performed on sintered structures. The Cu-Al2O3 composite with 5% copper density reached 61% of theoretical density and a hardness of 129 HV when sintered at 1300 ° C for 1h. In contrast, lower densities (59 and 51% of the theoretical density) and hardness (110 HV and 105) were achieved when the copper content increases to 10 and 15%.

Micronutrient contents in healthy and Crinipellis perniciosa infected tissues of Theobroma grandiflorum.

Micronutrient contents in leaf and branch tissues of cupuassu plants (Theobroma grand iflorum) infected by Crinipellis perniciosa, the causal agent of witches' broom disease, were determined to support further studies on the effect of nutritional status in the disease progress. Lower contents of boron and manganese and higher content of copper were found in infected leaf tissues. There was not any statistical difference in the copper content of branch tissues, even though higher copper content was found in healthy branches than in healthy leaf tissues. No changes in contents of iron and zinc in healthy of infected tissues were detected.

Effect of copper, cadmium and Cu.Cd mixture on amino acid content in the poslarvae of penaeid shrimp, Penaeus monodon and P. penicillatus

This study document effects of short-term (96h) sublethal levels of copper, cadmium and their mixture on the amino acid composition of postlarvae of the penaeid shrimp, P.monodon and P.penicillatus . All experimental conditions were kept constant, temperature between 25-27•C and salinity 21-22 ppt. The estimated LD50 for Cu was 200 ug/L, for Cd 177.5 ug/L and for Cu.Cd mixture 250ug/L. In P. penicillatus at the same concentration of each metal, there was significant reduction in amino acid content, which was 8.01% higher than the control. Almost similar reduction in some amino acids was observed in P.monodon. At the maximum concentration of 400 ug/L, cadmium caused higher reduction in amino acid composition than did copper. Thus, amino acid composition may be regarded as a sensitive biochemical indicator of Cu and Cd toxicity because of the effect of these metals on protein synthesis, a signal of physiological stress in marine organisms subjected to heavy metal pollution.

Peroxidase activity and total phenol content in citrus cuttings treated with different copper sources

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of tartrate content on aging and deposition condition of copper-tin electrodeposits from a non-cyanide acid bath

The effect of the presence of tartrate additive on the chemical stability of a Cu-Sn acid bath was evaluated. It was observed that this additive hinders decomposition of the Cu/Sn deposition bath with storage time, since the decrease in electrochemical efficiency was attenuated. In addition, it was observed that optimal galvanostatic deposition with or without tartrate occurs at approximately 11 mA cm(-2). However, in the presence of tartrate the deposition charge was lower, leading to lower energy consumption. SEM analysis showed that the tartrate added to the plating bath caused a marked change in the morphology of the Cu/Sn films obtained gal vanostatic ally. (C) 2002 Elsevier B.V. B.V. All rights reserved.

An Investigation into the Precipitation of Copper from Mine Water, using Sulfur Dioxide to Reduce the Ferric Ion Content

The experiments which were preformed showed that sulfur dioxide would reduce the ferric ion content of the mine waters to a very low figure. The reduction in the ferric ion content would improve the efficiency of the precipitation process, and also increase the recovery of copper.

Electronic structure of copper nitrides as a function of nitrogen content

he nitrogen content dependence of the electronic properties for copper nitride thin films with an atomic percentage of nitrogen ranging from 26 ± 2 to 33 ± 2 have been studied by means of optical (spectroscopic ellipsometry), thermoelectric (Seebeck), and electrical resistivity measurements. The optical spectra are consistent with direct optical transitions corresponding to the stoichiometric semiconductor Cu3N plus a free-carrier contribution, essentially independent of temperature, which can be tuned in accordance with the N-excess. Deviation of the N content from stoichiometry drives to significant decreases from − 5 to − 50 μV/K in the Seebeck coefficient and to large enhancements, from 10− 3 up to 10 Ω cm, in the electrical resistivity. Band structure and density of states calculations have been carried out on the basis of the density functional theory to account for the experimental results.

Characterization of Copper Covetic Bulk and Films: Copper with High Carbon Content

Incorporation of carbon nanostructures in metals is desirable to combine the strongly bonded electrons in the metal and the free electrons in carbon nanostructures that give rise to high ampacity and high conductivity, respectively. Carbon in copper has the potential to impact industries such as: building construction, power generation and transmission, and microelectronics. This thesis focuses on the structure and properties of bulk and thin films of a new material, Cu covetic, that contains carbon in concentrations up to 16 at.%. X-ray photoelectron spectroscopy (XPS) shows C 1s peak with both sp2 and sp3 bonded C measuring up to 3.5 wt.% (16 at.%). High resolution transmission electron microscopy and electron diffraction of bulk covetic samples show a modulated structure of ≈ 1.6 nm along several crystallographic directions in regions that have high C content suggesting that the carbon incorporates into the copper lattice forming a network. Electron energy loss spectra (EELS) from covetics reveal that the level of graphitization from the source material, activated carbon, is maintained in the covetic structure. Bulk Cu covetics have a slight increase in the lattice constant, as well as <111> texturing, or possibly a different structure, compared to pure Cu. Density functional theory calculations predict bonding between C and Cu at the edges and defects of graphene sheets. The electrical resistivity of bulk covetics first increases and then decreases with increasing C content. Cu covetic films were deposited using e-beam and pulsed laser deposition (PLD) at different temperatures. No copper oxide or any allotropes of carbon are present in the films. The e-beam films show enhanced electrical and optical properties when compared to pure Cu films of the same thickness even though no carbon was detected by XPS or EELS. They also have slightly higher ampacity than Cu metal films. EELS analysis of the C-K-edge in the PLD films indicate that graphitic carbon is transferred from the bulk into the films with uniform carbon distribution. PLD films exhibit flatter and higher transmittance curves and sheet resistance two orders of magnitude lower than e-beam films leading to a high figure of merit as transparent conductors.

Synthesis and spectroscopic characterization of copper zinc aluminum nanoferrite particles

Copper doped zinc aluminium ferrites are synthesized by the solid-state reaction route is cubic crystalline with unit cell parameter varying from 8.39 to 8.89 Å. TEM pictures clearly indicating that fundamental unit is composed of octahedral and tetrahedral blocks and joined strongly shown in (a). EPR spectra is compositional dependent at lower Al/Cu concentration EPR spectra is due to Fe3+ and at a higher content of Al/Cu the EPR spectra is due to Cu2+. Absence of EPR spectra at room temperature indicates that the sample is perfectly ferromagnetic. EPR results at low temperature indicate that the sample is paramagnetic, and that copper is placed in the tetragonal elongation (B) site with magnetically non-equivalent ions in the unit cell having strong exchange coupling between them. This is shown in (b). (a) TEM image of ferrite with x = 0.15. (b) EPR spectrum of ferrite with x = 0.75.

Copper-capped carbon nanocones on silicon : plasma-enabled growth control

Controlled self-organized growth of vertically aligned carbon nanocone arrays in a radio frequency inductively coupled plasma-based process is studied. The experiments have demonstrated that the gaps between the nanocones, density of the nanocone array, and the shape of the nanocones can be effectively controlled by the process parameters such as gas composition (hydrogen content) and electrical bias applied to the substrate. Optical measurements have demonstrated lower reflectance of the nanocone array as compared with a bare Si wafer, thus evidencing their potential for the use in optical devices. The nanocone formation mechanism is explained in terms of redistribution of surface and volumetric fluxes of plasma-generated species in a developing nanocone array and passivation of carbon in narrow gaps where the access of plasma ions is hindered. Extensive numerical simulations were used to support the proposed growth mechanism.

Nanostructured copper oxide semiconductors : a perspective on materials, synthesis methods and applications

The oxides of copper (CuxO) are fascinating materials due to their remarkable optical, electrical, thermal and magnetic properties. Nanostructuring of CuxO can further enhance the performance of this important functional material and provide it with unique properties that do not exist in its bulk form. Three distinctly different phases of CuxO, mainly CuO, Cu2O and Cu4O3, can be prepared by numerous synthesis techniques including, vapour deposition and liquid phase chemical methods. In this article, we present a review of nanostructured CuxO focusing on their material properties, methods of synthesis and an overview of various applications that have been associated with nanostructured CuxO.

XANES and EXAFS of copper compounds: Studies of copper carboxylates with metal-metal bonds and of the complex formed byPseudomonas aeruginosa

X-ray absorpion near edge structure (xanes) of copper compounds with copper in 1+, 2+ and 3+ states has been studied. Extended x-ray absorption fine structure (exafs) has been employed to determine bond distances and coordination numbers in several model copper compounds. Employing bothxanes andexafs, the structure of the copper complex formed by the micro-organismPseudomonas aeruginosa has been shown to be square-planar with the Cu-O distance close to that in cupric glucuronates and cupric acetylacetonate.exafs has been shown to be useful for studying metal-metal bonds in copper carboxylates.