Pure Aluminum Samples Research Articles

Neutron spectra produced by 30, 35 and 40 MeV proton beams at KIRAMS MC-50 cyclotron with a thick beryllium target

Neutrons over a wide range of energies are produced by bombarding a 1.05cm thick beryllium target with protons of different energies delivered by the MC-50 Cyclotron of the Korea Institute of Radiological Medical Sciences (KIRAMS). The neutron flux Φ(En) versus neutron energy En, produced by protons of 30, 35, and 40MeV energies, was obtained by using the GEANT4 code with a data-based hadronic model. For the experimental validation of the simulated neutron spectra, a number of pure aluminum and iron oxide samples were irradiated with the neutrons produced by 30, 35, and 40MeV protons at 20 μA beam current. The gamma-ray activities of 24Na and 56Mn produced, respectively, through 27Al(n,α)24Na and 56Fe(n,p)56Mn reactions were measured by a HPGe detector. The neutron flux Φ(En) at each neutron energy from the simulation was multiplied with the evaluated cross-sections σ(En) of the respective nuclear reaction, and the summation ∑Φ(En)σ(En) was calculated over the neutron spectrum for each proton energy of 30, 35, and 40MeV. The measured gamma-ray activities of 24Na and 56Mn were found in good agreement with the activities estimated by using the summed values of ∑Φ(En)σ(En) along with other parameters in a neutron activation method.

New Theoretical Modelling of Thermo-Elastic Behaviour Using the Geometric Average: Theoretical and Numerical Investigations

For the first time, Eshelby–Kroner self-consistent model extended to thermo-elastic loading is developed using the geometric mean for performing the set average operations. A new homogenization Eshelby–Kroner self-consistent approach is developed using a geometric average during thermo-mechanical loading. The description of the material thermo-elastic behaviour is carried out through new, appropriate, geometric polarisation tensors. In this paper, the classical Eshelby–Kroner thermo-elastic model based upon the arithmetic mean is used as a reference. A discussion and comparison between both average types is also provided. In particular, the coefficient of thermal expansion of silicon carbide, identified in the range 398–998 K from the knowledge of the thermal expansion of aluminium–silicon carbide metal matrix composites and pure aluminium samples do not depend on the average type chosen for achieving the computations.

Polarization characteristics of four types of coating films by thermal spray in seawater solution

Thermal spray coating method has been known to be an attractive technique due to its relatively high coating speed. However, a high corrosion resistance of the coating film deposited by thermal spray method should be improved to prolong its lifetime. In this study, four types of coated films (DFT: 400 μm), that is, pure zinc, pure aluminum and two Al – Zn alloy ( Al : Zn = 85:15 and Al : Zn = 95:5) films were coated onto a carbon steel (SS401) with arc spraying, and the corrosion behaviors of these samples were investigated using the electrochemical method. The pure aluminum sample had the best corrosion resistance in seawater solution and alloy ( Al : Zn = 85:15) film, so called galvalume followed the pure aluminum sample, moreover, the alloy ( Al : Zn = 95:5) sample exhibited the worst corrosion resistance.

Influence of Microstructure and Composition on Optical Properties of Plasma Sprayed Al/Al2O3 Cermets

Normal hemispherical spectral reflectances of plasma sprayed Al2O3/Al cermets were acquired from visible to infrared wavelengths for several metal concentrations. Since optical response of these coatings is highly dependent on volumetric and/or surface light scattering, special attention was paid to characterization of the composition, microstructure, and surface roughness of such coatings. The roles of volumetric and surface effects are highlighted by a comparison between the spectral data measured on as-sprayed coatings and on polished coatings. As expected, reflectance rises with the metal addition, but in the transparent region of alumina, a noteworthy behavior is noticed for low aluminum concentrations. Indeed, the reflectance presents strong composition dependence and remains lower than that of the pure alumina sample. The results show that the optical properties of cermets produced by plasma spraying are controllable and therefore open the door to applications in the areas of solar energy or aerona...

A Precipitation Phenomenon of Titanium Compounds in Aluminum Melts and the Refinement Fading Mechanism of the Al-5Ti-0.62C Master Alloy

The Al-5Ti-0.62C master alloy was prepared through a method of thermal explosion in molten aluminum. The process of remelting and refining of commercially pure aluminum was conducted, and precipitation samples with different heat-treatment times were obtained. Scanning electron microscopy (SEM), X-ray diffraction (XRD), optical microscopy (OM), and other techniques were used to analyze the microstructure of the precipitates at the bottom of the samples so as to explore the fading mechanism of Al-Ti-C alloy refinement. The results showed that an obvious precipitation phenomenon of titanium compounds existed in the remelted Al-5Ti-0.62C master alloy and that there were both TiC compounds and TiAl3compounds in the precipitates; in the refined pure aluminum samples, the precipitates were mainly TiC compounds. Precipitation of titanium compounds in aluminum melting is the main cause of fading in the refinement effect of an Al-Ti-C master alloy.

Consolidated Al/Al2O3 Nanocomposites by Equal Channel Angular Pressing and Hot Extrusion

This work is aimed at producing Al-matrix nanocomposites through the powder metallurgy (PM) process. An initial study on pure aluminum powder was performed to analyze the performance of different PM techniques. In particular, Al powder was refined via high-energy ball milling and consolidated by hot extrusion and equal channel angular pressing. The latter revealed to be a very efficient procedure for powder compaction (high density and hardness of the products) and it was adopted for the production of Al-based composites reinforced with 2% and 5 wt% of Al2O3 nanoparticles. The composites exhibited higher hardness than the pure aluminum sample.

Unexpected temporal evolution of atomic spectral lines of aluminum in a laser induced breakdown spectroscopy experiment

The temporal evolution of the laser induced breakdown (LIBS) signal of a pure aluminum sample was studied under nitrogen and air atmospheres. In addition to the usual decrease of signal due to plasma cooling, unexpected temporal evolutions were observed for a spectral lines of aluminum, which revealed the existence of collisional energy transfer effects. Furthermore, molecular bands of AlN and AlO were observed in the LIBS spectra, indicating recombination of aluminum with the ambient gas. Within the experimental conditions reported in this study, both collisional energy transfer and recombination processes occurred around 1.5μs after the laser shot. This highlights the possible influence of collisional and chemical effects inside the plasma that can play a role on LIBS signals.

Analysis and Nanomold Design for Aluminum Nanoimprinting

A nano-forging process based on the potential function of an embedded atom method (EAM) and mechanism, for pure aluminum samples, was studied using molecular dynamic (MD) simulation. The effects of forging temperature and velocity were evaluated in terms of molecular trajectory, internal energy, and a radial distribution function. The simulation results clearly show that the internal energy exerted by the workpiece during the forging process rises with a decrease of forging temperature, and an increase of forging velocity also raises the internal energy. During the forging process, a special atomic structure in the (011) and (011) slip planes was observed that represents the site of dislocation generation and growth nucleation. When severe plastic deformation occurs, the density of the workpiece changes. The forged workpiece has similar distributions of atomic density after loading at different forging temperatures and velocities.

Nanostructured Al–Zn–Mg–Cu–Zr alloy prepared by mechanical alloying followed by hot pressing

Nanostructured Al–7.8wt% Zn–2.6wt% Mg–2wt% Cu–0.1wt% Zr alloy was mechanically alloyed (MA) from elemental powders and consolidated by hot press technique. The effect of the milling time and hot pressing process on microstructure was investigated by means of X-ray diffraction measurements (XRD) and analytical and scanning electron microscopy (SEM). Furthermore mechanical properties of samples with different MA time as well as pure aluminum were investigated by microhardness and compression tests. The results show that an Al–Zn–Mg–Cu–Zr homogenous supersaturated solid solution with a crystallite size of 27nm was obtained after 40h of milling time. Microstructure refinement and morphological changes of powders from flake to spherical shape were observed by increasing milling time. Phase and microstructural characterization of high density bulk nanostructured samples revealed that increasing milling time up to 40h leads to formation of MgZn2 precipitation in the alloy matrix. With increasing milling time, density of the samples and crystalline size decrease. Significant enhancement of hardness and compressive strength is observed in the aluminum alloy by increasing milling time up to 40h which is much higher than pure aluminum. Crystallite size refinement in pure aluminum samples from micro- to nanoscales resulted in 107% and 100% improvement in compressive strength and hardness, respectively. Furthermore the compressive strength and hardness of Al–Zn–Mg–Cu–Zr alloy nanostructured samples increased to 179% and 172%, respectively, compared to nanostructured pure Al, which was produced as reference specimen. 40h of MA was the optimum case for preparing such an Al alloy and more milling up to 50h led to deterioration of mechanical properties.

Trace element determination in high-purity aluminum clad samples by k 0-based internal monostandard instrumental neutron activation analysis

The k0-based internal monostandard instrumental neutron activation analysis (IM-INAA) method was applied for quantification of trace impurities in seven high purity aluminum samples used as fuel cladding in a research reactor. Samples along with BCS CRM 182 (Si–Al alloy) were irradiated in high flux reactor neutrons for 10–15 h. In situ detection efficiency, needed in concentration calculation ratio by IM-INAA, was obtained using gamma rays of activation products produced in the samples. Elemental concentration ratios obtained with respect to Fe (used as internal monostandard) were converted to absolute concentrations by determining concentration of Fe by relative method of NAA. Concentrations of ten trace elements (Sc, Cr, Co, Zn, Ga, La, Ce, Sm, W and Hf) including major element Fe were determined in this work. The method used is non-destructive in nature and does not need multielement standards. Results of IM-INAA were compared with those obtained by relative method of INAA and inductively coupled plasma atomic emission spectrometry (ICP-AES). Details of methodologies and results obtained by all methods are discussed and compared in the paper.

Nickel aluminate spinel reinforced ceramic hollow fibre membrane

Ceramic hollow fibre membranes are suitable for application in many industrial processes that involve harsh conditions such as high temperatures and concentrated organic solvents because of their high thermal and chemical stability. The major limitation of ceramic hollow fibre membrane is the brittle nature of ceramic materials, which leads to difficulty in large scale production and failure in pressurised processes. This paper presents the reinforcement of alumina (Al2O3) hollow fibre membrane by nickel aluminate spinel (NiAl2O4). The ceramic hollow fibre membrane was fabricated by the widely used phase inversion method. The NiAl2O4 phase was formed by the reaction of nickel (II) oxide (NiO) with Al2O3 during sintering. A maximum flexural strength of 156MPa was achieved by the NiAl2O4/Al2O3 hollow fibre membrane containing 16.4wt% of NiAl2O4, which was 2.3 times of that of the pure alumina sample. The 16.4wt% NiAl2O4/Al2O3 hollow fibre membrane had a porosity of 46.8%, a mean pore size of 330nm determined by a gas bubble pressure method, and a pure water flux of 597L/m2hbar at a testing pressure of 2bar. NiAl2O4/Al2O3 hollow fibre membrane could achieve a flexural strength comparable to higher-cost yittria stabilized zirconia and silicon nitride hollow fibres within the porosity range of 46.8–55.2%.

Effect of impurity levels on the structure of solidified aluminum under pulse magneto-oscillation (PMO)

The effect of pulse magneto-oscillation (PMO) treatment on the solidified structure and the cooling curves of pure aluminum samples of two grades were investigated. The PMO treatment leads to decrease in the supercooling level and to refinement of the solidified structure. The effect of the PMO treatment strongly depends on the purity level of aluminum. A model is proposed to explain the effect of the PMO treatment on the structure of solidified metals.

Characteristics Evaluation of Coating Film by Thermal Spray in Seawater Solution

Many surface protection methods have been developed to apply to constructional steels to be used under severe corrosive environments. Thermal spray coating has been known to be an attractive technique due to its relatively high coating speed. However, the high corrosion resistance of coating films deposited by thermal spray method is increasingly required to expand its application. Four types of coated films (DFT: 200um), that is, pure zinc, pure aluminum, and two Al-Zn alloy (Al:Zn=85:15 and Al:Zn=95:5), were coated onto carbon steel (SS401) with arc spraying, and the corrosion behavior of their samples were evaluated by the electrochemical method in this study. The pure aluminum sample had the best corrosion resistance when exposed to seawater solution and alloy (Al:Zn=85:15), so called galvalume and alloy (Al:Zn=95:5) samples followed the pure aluminum sample. The pure zinc sample ranked 4thin corrosion resistance in this study. Morphology of corroded surfaces of pure aluminum and alloy (Al:Zn=85:15) samples exhibited a general corrosion pattern, however, the patterns of intergranular and pitting corrosion were observed for the pure zinc and alloy (Al:Zn=95:5) samples respectively. Pure zinc sample had the smallest value of porosity ratio compared to other samples due to its heavier density. Keywords : Surface protection methods, Thermal spray, Corrosion resistance, Pure aluminum, Pure zinc, Porosity ratio

Stability of Fatigued Dislocation Wall Structure in Coarse-Grained and Ultrafine-Grained Aluminum against Monotonic Tensile Deformation

Coarse-grained (CG) and ultrafine-grained (UFG) pure aluminum samples fabricated by equal channel angular pressing (ECAP) were cyclically deformed at 77K under constant plastic strain amplitude. Monotonic tensile tests were performed at 300 and 77K soon after the fatigue tests. In spite of the increase in the tensile strength of fatigued CG Al, tensile ductility decreased remarkably in comparison to that of as-annealed CG Al. On the other hand, the ultimate tensile strength (UTS) and tensile ductility of UFG Al were much higher at 77K than those at 300K. Furthermore, UFG Al at 77K maintained high UTS and high tensile ductility even after fatigue tests. Microstructural observation has revealed that dislocation wall structure formed in fatigued CG Al persists after the monotonic tensile tests. However, dislocation wall structure formed in fatigued UFG Al disappeared during early stages of monotonic tensile tests at both 300 and 77K. These results indicate that the dislocation wall structure in UFG Al is unstable against succeeding monotonic tensile deformation. [doi:10.2320/matertrans.M2012280]

Influence of Stress on Aluminum Anodization and Pore Ordering

The influence of pre-stressing an aluminum substrate on pore ordering of a porous anodic alumina (PAA) membrane has been investigated. Samples of pure aluminum were constrained and unconstrained stressed until plastic deformation before potentiostatic anodization. Characterizations of the resulting PAA membranes were performed during and at the end of the electrochemical process. Results suggest that as the first alumina layer detaches from the substrate due to the increased electrochemical reactivity on a pre-stressed surface, a second layer grows on the pattern of the previous with an increase in pore ordering. Combining a two-step anodization into a single process can be beneficial in porous alumina membrane fabrication.

A new aluminum-based metal matrix composite reinforced with cobalt ferrite magnetic nanoparticle

A new composite with cobalt ferrite magnetic nanoparticle dispersed in an aluminum matrix has been prepared using the ball-milling technique followed by compaction and sintering. Our efforts were largely focused on investigating the contribution of cobalt ferrite to the enhancement of structural, mechanical and magnetic properties of aluminum. Incorporation of 1–10 weight (wt)% of nanosized cobalt ferrite into the aluminum matrix could affect remarkable change in mechanical properties. Enhancement of hardness value, elastic modulus, and compressive strength was observed in the case of cobalt ferrite-incorporated aluminum matrix as compared to the pure aluminum sample. Incorporation of cobalt ferrite could impart considerable improvement of magnetization value of the aluminum matrix with a saturation magnetization of 17.07 emu/g for the aluminum sample reinforced with 10 wt% of cobalt ferrite. A decrease in coercive force in the sample arising from the increase in surface effects and inter-particle interaction between the ferromagnetic cobalt ferrite and soft phases in the matrix was also observed.

Effects of initial grain size on hot deformation behavior of commercial pure aluminum

The effects of initial grain size of commercial pure aluminum on hot deformation behavior were investigated using hot compression tests. The hot compression tests were carried out on the pure aluminum samples with the initial grain sizes of 50, 150 and 450μm using various strains, strain rates and different deformation temperatures. It was found that the hot deformation behavior of used material was sensitive to deformation conditions and initial microstructure. Results indicate that the initial grain size has significant effect on the flow stress. Flow stress decreases when the grain size decreases from 450 to 50μm and when strain rate is lower than 0.05s−1. This procedure is reversed at strain rate of 0.5s−1. Furthermore, effects of other parameters like the strain rates and deformation temperatures on the flow stresses and hardening rates were investigated. It was also found that the inhomogeneity of microstructure distribution at different positions of the deformed specimens depended on the amount of deformation concentration at particular points and other processing parameters such as initial grain sizes, strain rates and deformation temperatures. In addition the geometric dynamic recrystallization (GDRX) was observed in the specimens highly strained (0.7) at elevated temperature (500°C) using polarized light microscope and sensitive tint (PLM+ST).

OBSERVATION OF THE CORROSION CHARACTERISTICS OF METALIZING FILM IN SEAWATER SOLUTION

Four types of coated films (DFT: 300um), that is pure zinc, pure aluminum, and two Al - Zn alloy ( Al : Zn =85:15 and Al : Zn =95:5), were coated onto carbon steel (SS401) with arc spraying, and the corrosion behavior of their samples were evaluated by the electrochemical method in this study. The pure aluminum sample had the high corrosion resistance when exposed to seawater solution and pure zinc and alloy ( Al : Zn =95:5) samples followed the pure aluminum sample. The other alloy ( Al : Zn =85:15), the so-called galvalume that was coated onto the carbon steel, ranked 4th in corrosion resistance in this study. The results of the porosity ratio of those samples are well matched with the electrochemical data

Analysis on Behavior of Hydrogen in Ion-Plated Pure Aluminum

An increasing interest has been being taken in hydrogen as a clean energy for solving the global environmental problems. In order to use the hydrogen in safety, investigation on the hydrogen behavior is required. Although hydrogen microprint technique (HMPT) has been known to be effective to investigate the hydrogen behavior, the low detection efficiency for hydrogen was reported. Ion-plating (IP) was reported to increase the detection efficiency in HMPT emitted from the specimen by plastic deformation. On the other hand, no such increase was found for hydrogen permeating through the specimen ion-plated with substrate heating in the previous study by the authors. In the present study, the sheet samples of pure aluminum with 99.99% purity were dehydrogenated and subjected to (a) holding in the IP chamber, (b) bombardment with Ar ions, (c) substrate heating after the bombardment and (d) holding in air. Hydrogen behavior in these samples has been investigated by means of thermal desorption spectroscopy (TDS). The amount of desorbed hydrogen was evidently larger in the conditions of (a) and (b) than in (d). However, the amount of desorbed hydrogen was decreased by the substrate heating (c) to the same level as in (d).

Identification of the C 2∏–X 2Σ + band system of AlO in the ultraviolet galvanoluminescence obtained during aluminum anodization

The first galvanoluminescence spectrum in the ultraviolet region obtained during anodization of high purity aluminum samples annealed at temperature above 525 °C is presented. An intense broad peak with the maximum at about 31,900 cm −1 is assigned to the transitions (some of them heretofore unobserved) between vibrational levels of the C 2∏ → X 2Σ + spectral system of AlO, partly overlapped with the A 2Σ + → X 2∏ system of OH.