Pure Aluminum Alloy Research Articles

Effect of the axial external magnetic field on copper/aluminium arc weld joining

Pure copper and aluminium alloy was joined by cold metal transfer welding with the assistance of an axial external magnetic field in this work. The results reveal that magnetic field led to a reduction of the average heat input and improved the wetting behaviour of the weld metal on the copper sheet surface. The thickness of the Al2Cu intermetallic compound layer formed at the interface was decreased from 50 µm for normal welding to 5 µm for the magnetic field-assisted welding process. The joint strength was observed to increase with the magnetic field. For a 21 mT and 10 Hz magnetic field, the maximum loading force reached up to 1.67 kN, resulting in an increase in joint strength by 33%.

Molecular dynamic simulation of edge dislocation-void interaction in pure Al and Al-Mg alloy

In this study, the interaction of edge dislocations with nano-scale voids was investigated for the face centered cubic (FCC) structure of pure aluminum and Al-Mg alloy. The effect of Mg solute atoms on the Peierls stress (required for dislocation motion) at different temperatures, and the critical resolved shear stress (CRSS) for dislocation-void interaction was investigated in this study. In addition, the influences of void diameter (1, 2 and 3nm), inter-void distance (7.5 and 15nm) in a void array, and of temperature (300K) on resolved shear stress were determined. It was found that substitutional Mg atoms was highly effective on improving the mechanical behavior of the Al lattice and on the type of dislocation-void interaction (simultaneous or separate passing of partial dislocations). In addition, it was obtained that no void-induced climbing occurred during the interactions for these systems. Higher void diameter and in particular lower inter-void spacing led to a considerable increase in the CRSS, while the latter changed the type of dislocation-void interaction. Finally, it was shown that Peierls stress was decreased for pure aluminum from 0K to 10K, while different results were obtained for Al-Mg alloy that were discussed in detail.

INVESTIGATION OF THE EFFECT OF ADDING CU ON AL ALLOYS FOR WEAR AND FRICTION PROPERTIES

In this study, Cu alloys in different ratios (2, 4, 6 and 8%) were added into the commercial purity (99.8% Al) aluminum alloys and Al-Cu alloys were prepared by sand mold casting method. In the current study, chemical composition is determined by spectrometer, density and hardness are measured, the wear and friction behavior are investigated, and finally microstructure of Al-Cu alloys is examined by optical microscopy. Wear tests were made under dry sliding, at pin-on-disk wear device and against X40CrMoV5-1 steel disc. In wear tests, 20, 40 and 60N loads, 0.5-1.5 m/s sliding speed were used, respectively. As a result, coefficient of friction of pure Al and Cu filled Al alloys increased by load and sliding speed. Wear ratio decreased with load while increased by the sliding speed. Wear rates of Cu filled Al alloy were determined about 10 -13 m 2 /N.

Determination of the critical undeformed chip thickness in micromilling by means of the acoustic emission signal

In the last decades, micromachining has gained increased relevance as an alternative method to produce miniaturized parts for a wide range of products. Nevertheless, micromachining differs considerably from conventional machining in many aspects. This work is concerned with the investigation of size effect when micromilling three distinct materials (pure nickel, electrolytic copper and AA 6262-T6 aluminium alloy). The friction coefficient between each work material and (Ti,Al)N coated tungsten carbide (cutting tool material) was determined and employed to calculate the critical chip thickness. Micromilling tests were performed and additionally to the specific cutting force, the critical chip thickness was identified using the acoustic emission signal. The findings indicate the suitability of the model based on the friction coefficient and cutting edge radius to determine the critical undeformed chip thickness. For each work material, it was found that feed rate values below the critical undeformed chip thickness led to ploughing (higher acoustic emission signal), whereas feed rate values above the critical undeformed chip thickness cause chip formation. Furthermore, the reduction in the shear plane area resulted in higher specific cutting force.

Microstructure and Mechanical Properties of Accumulative Roll-Bonded AA1050A/AA5005 Laminated Metal Composites

Laminated metal composites (LMCs) with alternating layers of commercial pure aluminum AA1050A and aluminum alloy AA5005 were produced by accumulative roll-bonding (ARB). In order to vary the layer thickness and the number of layer interfaces, different numbers of ARB cycles (4, 8, 10, 12, 14 and 16) were performed. The microstructure and mechanical properties were characterized in detail. Up to 8 ARB cycles, the ultrafine-grained (UFG) microstructure of the layers in the LMC evolves almost equally to those in AA1050A and AA5005 mono-material sheets. However, the grain size in the composites tends to have smaller values. Nevertheless, the local mechanical properties of the individual layers in the LMCs are very similar to those of the mono-material sheets, and the macroscopic static mechanical properties of the LMCs can be calculated as the mean value of the mono-material sheets applying a linear rule of mixture. In contrast, for more than 12 ARB cycles, a homogenous microstructure was obtained where the individual layers within the composite cannot be visually separated any longer; thus, the hardness is at one constant and a high level across the whole sheet thickness. This results also in a significant higher strength in tensile testing. It was revealed that, with decreasing layer thickness, the layer interfaces become more and more dominating.

IEC 61267: Feasibility of type 1100 aluminium and a copper/aluminium combination for RQA beam qualities

In the course of performance acceptance testing, benchmarking or quality control of X-ray imaging systems, it is sometimes necessary to harden the X-ray beam spectrum. IEC 61267 specifies materials and methods to accomplish beam hardening and, unfortunately, requires the use of 99.9% pure aluminium (Alloy 1190) for the RQA beam quality, which is expensive and difficult to obtain. Less expensive and more readily available filters, such as Alloy 1100 (99.0% pure) aluminium and copper/aluminium combinations, have been used clinically to produce RQA series without rigorous scientific investigation to support their use. In this paper, simulation and experimental methods are developed to determine the differences in beam quality using Alloy 1190 and Alloy 1100. Additional simulation investigated copper/aluminium combinations to produce RQA5 and outputs from this simulation are verified with laboratory tests using different filter samples. The results of the study demonstrate that although Alloy 1100 produces a harder beam spectrum compared to Alloy 1190, it is a reasonable substitute. A combination filter of 0.5 mm copper and 2 mm aluminium produced a spectrum closer to that of Alloy 1190 than Alloy 1100 with the added benefits of lower exposures and lower batch variability.

Metallurgical bond between magnesium AZ91 alloy and aluminium plasma sprayed coatings

We report on creation of metallurgic bond between AZ91 magnesium alloy and aluminium plasma sprayed coatings which has been so far observed only after additional surface treatments. High-enthalpy plasma spray process employing water-stabilized plasma torch was used to spray commercially pure aluminium and AlCr6Fe2 alloy and, thus, creating around 200 and 450μm thick coatings, respectively, with presence of aluminium oxides. For both coatings, metallurgical bond layers with thickness of around 100μm and notable for their eutectic morphology were obtained. Analyses of microstructure, elemental and phase compositions revealed that the bond layer with the commercially pure aluminium coating is dominantly Al12Mg17 while the bonding with AlCr6Fe2 alloy comprises both Al12Mg17 and Al3Mg2. Despite the presence of porosity, the coatings' polarization resistance measurements showed increased values as compared with the bare substrate. Results of adhesion tests did not confirm the deterioration of adhesion strength due to the presence of intermetallics in the bond, and more important factor was the phase composition and microstructure of the coatings. The thickness of the metallurgic bond can be thermally controlled via the substrate preheating and/or its thickness.

The effect of preheating on mechanical properties of friction stir welded dissimilar joints of pure copper and AA7075 aluminum alloy sheets

In this paper, apart from introducing brand-new warm friction stir welding (WFSW) method, the effect of preheating on the mechanical properties of dissimilar friction stir welded copper/aluminum alloy sheets was investigated. Sheets of aluminum alloy 7075 and copper both with the thickness of 5 mm were used. The utilized welding tool was made of a H-13 tool steel with a threaded cone shape. Rotational speeds (ω) of 1200–1400 rpm and travel speeds (v) of 50–100 mm/min were used for better understanding of the effect of welding parameters on heat input. The sheets were kept in furnace with temperatures of 75 and 125 °C, and welding was done afterward. At last, tensile test was done to compare the mechanical properties of the welds. The tensile test results showed 100 % increase in the strength of preheated joints in comparison with the non-preheated joints which were welded at room temperature. Considering the high thermal conductivity of both copper and aluminum, the reason of increase in strength of the joints could be related to the low temperature gradient between the weld zone and base metal because the heat gets out of the stir zone with lower steep. The maximum strength occurred for the specimen with the preheating of 75 °C, rotational speed of 1300 rpm, and travel speed of 75 mm/min.

Gradual formation of nano/ultrafine structure under accumulative press bonding (APB) process

Accumulative press bonding (APB) is a developed reuse of the oldest severe plastic deformation (SPD) process to produce nano/ultrafine grained (UFG) materials. In the present work, microstructural evolution and mechanical properties of AA1050 pure aluminum alloy have been investigated under APB technique up to 14cycles. From scanning transmission electron microscopy characterization, it was found that continuous dynamic recovery was a dominant mechanism in grain refinement, and resulted in formation of nano/ultrafine grains with average diameter of 450nm in pressing direction and 320nm in transverse direction. After 14 APB cycles, almost 10% of all grains were less than 100nm. Electron backscattered diffraction revealed that the fraction of high angle boundaries and the mean misorientation angle increased by increasing strain during APB process and reached a saturation value of ~78% and ~35°, respectively. By increasing the number of APB cycles, the tensile strength of the APB processed aluminum improved and reached 180MPa after 14cycles, which was two times higher than obtained values for initial materials, i.e. 88MPa. On the other hand, the elongation dropped abruptly at the first cycle and then increased slightly. Strengthening in APB processed aluminum was attributed to strain hardening by dislocation accumulation dominant in primary cycles, and grain refinement which was dominant in final cycles. Scanning electron microscopy observations demonstrated that failure mode in APB processed aluminum was shear ductile rupture with small elongated dimples.

Interdiffusion and Reaction between Pure Magnesium and Aluminum Alloy 6061

Using solid-to-solid couples investigation, this study characterized the reaction products evolved and quantified the diffusion kinetics when pure Mg bonded to AA6061 is subjected to thermal treatment at 300°C for 720 hours, 350°C for 360 hours, and 400°C for 240 hours. Characterization techniques include optical microscopy, scanning electron microscopy with X-ray energy dispersive spectroscopy, and transmission electron microscopy. Parabolic growth constants were determined for γ-Mg17Al12, β-Mg2Al3, and the elusive ε-phase. Similarly, the average effective interdiffusion coefficients of major constituents were calculated for Mg (ss), γ-Mg17Al12, β-Mg2Al3, and AA6061. The activation energies and pre-exponential factors for both parabolic growth constant and average effective interdiffusion coefficients were computed using the Arrhenius relationship. The activation energy for growth of γ-Mg17Al12 was significantly higher than that for β-Mg2Al3 while the activation energy for interdiffusion of γ-Mg17Al12 was only slightly higher than that for β-Mg2Al3. Comparisons are made between the results of this study and those of diffusion studies between pure Mg and pure Al [1] to examine the influence of alloying additions in AA6061.

Microstructure and mechanical properties of Al/Ti joints welded by resistance spot welding

Resistance spot welding of commercial pure titanium and aluminium alloy 6061-T6 is carried out. The microstructure and tensile shear properties of the weld joints are studied. There is a critical range of welding current at which the reaction between liquid aluminium and solid titanium changes to a reaction between liquid aluminium and liquid titanium. The microstructure in the aluminium side is a type of transition structure, which is considered to be the same microstructure that connects the columnar dendrite and equiaxed dendrite in similar aluminium alloy resistance spot welding. The welding current has the largest influence upon the tensile shear properties of the Al/Ti weld joint, while the welding time has a small effect and the electrode force has virtually no effect.

The influence of material hardness on liquid droplet impingement erosion

This paper describes the experimental study on the liquid droplet impingement erosion of metal materials to understand the influence of material hardness on the erosion rate. The experiment is carried out using a water spray jet apparatus with a condition of relatively thin liquid film thickness. The metal materials tested are pure aluminum, aluminum alloy, brass, mild steel, carbon steel and stainless steel. The liquid droplets considered are 30±5μm in volume average diameter of water, which is the same order of droplet diameter in the actual pipeline in nuclear/fossil power plants. In order to understand the influence of material hardness on the liquid droplet impingement erosion, the scanning electron microscope (SEM) observation on the eroded surface and the measurement of erosion rate are carried out in the terminal stage of erosion. The experimental results indicate that the erosion rates are expressed by the droplet velocity, volume flux, Vickers hardness and the liquid film thickness, which are fundamentals of the liquid droplet impingement erosion. The empirical formula shows that the power index for droplet velocity dependency is found to be 7 with a scattering from 5 to 9 depending on the materials, while the power index for Vickers hardness dependency is found as −4.5.

Characterisation of friction stir spot welding process based on envelope analysis of vibro-acoustical signals

The evaluation of the relationship between the vibro-acoustical signals generated by friction stir spot welding (FSSW) process with its parameters and stages such as torque, dwell time, and tool rotation speed, is developed in this work. A dissimilar lap-joint was conducted using pure copper and AA1050 H24 aluminium alloy. The vibro-acoustical signals in Z and Y directions, and torque applied by the tool during the process have been acquired by the instrument NI USB-9234. The characterisation in the time and frequency domains of the vibro-acoustical signals has been performed in order to correlate them with the stages of processing and tool torque. The analysis has confirmed that the vibro-acoustical signals were significantly affected by changes in process forces and can thus be used as a non-destructive method for process monitoring, optimisation tasks, and control of FSSW process.

Electrical resistivity measurements of Al-cast alloys during solidification

The aim of this paper was the selection of proper electrodes material regarding four–probe technique for the electrical resistivity measurements of Al–Si cast alloys. The most significant problem for electrodes is oxidation during measurements causing high contact resistance and providing incorrect results. Various materials were tested and aluminium electrodes chosen. The advantage of aluminium electrodes is that they melt within the specimen immediately after being poured and cause no interface resulting with any contact resistance. Pure aluminium and eutectic AlSi12 alloys were tested. Resistivity of Al–Si alloys is increasing with Si content. Grain refinement and modification of βSi were employed. Grain refinement has any effect on electrical resistivity. Modification of βSi phase causes decrease of electrical resistivity.

Characterization of Mechanical Properties and Microstructure of Aluminium Alloy-SiC Composites

In recent years aluminium alloys are widely used in automotive industries due to light weight, good formability, high corrosion resistance and high electrical and thermal conductivity. However, the poor mechanical and tribological properties of pure aluminium alloys limit its wider range of applications. The mechanical properties can be improved by addition of ceramic particles like SiC, Al2O3 etc. AMCs combine the metallic properties of matrix alloys (ductility and toughness) with ceramic properties of reinforcements (high strength and high modulus) and lead to higher strength in tension and compression and higher service temperature capabilities. In this study, AA 5083 alloy-SiC composites have been fabricated by Ultrasonic assisted Stir casting. Different weight % of SiC (3, 5, 8 and 10wt %) were used for synthesis of composites. SEM micrographs show uniform distribution of SiC particles with agglomeration at some places. The application of ultrasonic vibration on the composite during melting not only refined the grain structure of the matrix, but also improved the distribution of nano-sized reinforcement.

Effect of Milling Time on Structural Evolution and Mechanical Properties of Garnet Reinforced EN AW6082 Composites

The morphology, structure, and hardness variations of garnet reinforced EN AW6082 Al-alloy composites have been investigated. High-energy ball milling of EN AW6082 Al-alloy powder, with and without garnet reinforcement, was performed under argon atmosphere for various duration, i.e., up to 50 hours. The study aimed at exploring the role of alloying elements and hard reinforcement particles on the structural evolution at different stages of mechanical milling. The composite powders were characterized in terms of the morphological variation, microstructural evolution, and thermal stability. Conventional microindentation and nanoindentation measurements were carried out on the individual powders as well as composite particles to estimate the changes in the mechanical properties of the composites with milling time. The results reveal that incorporation of hard garnet particles hastens the milling effect and leads to significant improvement in hardness and modulus of unreinforced pure aluminum and aluminum alloy. This work has demonstrated the possibility of producing composites from industrial by-product, with properties better than those of aluminum alloys and aluminum-based composites.

Effect of Heat Treatment on Positron Annihilation Lifetime of an Extruded Al-12.7Si-0.7Mg Alloy

Positron annihilation lifetime can reflect the information of electronic density. Therefore this technique is very sensitive to the vacancies. Therefore positron annihilation technology (PAT) is a non-destructive testing technology for the investigation on the vacancy in pure metals and alloys. The vacancy defects of as-cast pure aluminium and the extruded Al-12.7Si-0.7Mg alloy before and after heat treatment were investigated by positron annihilation lifetime spectra. The results of positron annihilation lifetime spectra show that the lifetime of free positron annihilation in the pure aluminium alloy is 155 ps. The positron annihilation lifetime of the extruded sample is longer than the lifetime in the pure aluminium due to the formation of grain boundary and dislocation during the extrusion process. The positron annihilation lifetime of the extruded sample after heat treatment is shorter than that before the heat treatment, and it is longer than that of the pure sample.

Fabrication and Structural Studies of Porous Anodic Oxide Film on Pure Aluminium and Aluminium Alloy (AA 1100)

Pure aluminium and aluminium alloy 1100 samples were anodized by one step and two step process. The foils were anodised in 0.3 M sulphuric acid solution at constant voltage of 25V and the temperature was maintained at 20 o C. The effect of increase of exposure time in second anodization step on the structural features was studied on AA 1100. A well ordered nanoporous structure were produced. It was found that in two step anodization process the produced film have very regular hexagonal cells with uniform pores as compare to single step anodization in both Al and AA 1100. The two step anodization improves both pore diameter and uniformity. With the increase in second step anodization time the complexities of porous film increases due to formation of sub pores.

Characterization of Coatings on Grey Cast Iron Fabricated by Hot-dipping in Pure Al, AlSi11 and AlTi5 Alloys

Abstract Flake graphite cast iron was hot-dip coated with pure aluminium or aluminium alloys (AlSi11 and AlTi5). The study aimed at determining the influence of bath composition on the thickness, microstructure and phase composition of the coatings. The analysis was conducted by means of an optical microscope and a scanning electron microscope with an EDS spectrometer. It was found that the overall thickness of a coating was greatly dependent on the chemical composition of a bath. The coatings consisted of an outer layer and an inner intermetallic layer, the latter with two zones and dispersed graphite. In all the cases considered, the zone in the inner intermetallic layer adjacent to the cast iron substrate contained the Al5Fe2 phase with small amount of silicon; the interface between this phase and the cast iron substrate differed substantially, depending on the bath composition. In the coatings produced by hot-dipping in pure aluminium the zone adjacent to the outer layer had a composition similar to that produced from an AlTi5 bath, the Al3Fe phase was identified in this zone. The Al3Fe also contained silicon but its amount was lower than that in the Al5Fe2. In the coatings produced by hot-dipping in AlSi11, the zone adjacent to the outer layer contained the Al3FeSi phase. The analysis results showed that when AlSi11 alloy was applied, the growth mode of the inner layer changed from inwards to outwards. The interface between the Al5Fe2 phase and the cast iron substrate was flat and the zone of this phase was very thin. Locally, there were deep penetrations of the Al5FeSi phase into the outer layer, and the interface between this phase and the outer layer was irregular. Immersion in an AlTi5 bath caused that the inner intermetallic layer was thicker than when pure aluminium or AlSi11 alloy baths were used; also, some porosity was observed in this layer; and finally, the interface between the inner layer and the cast iron substrate was the most irregular

Development of Cerium-Rich Layers on Anodic Films Formed on Pure Aluminium and AA7075 T6 Alloy

The development of cerium-rich layers on anodized pure aluminum and AA7075 T6 aluminum alloy has been investigated using scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The surfaces of pure aluminum and AA7075 T6 were pre-treated by alkaline etching and HNO3 desmutting followed by anodizing in sulfuric acid electrolyte with and without addition of tartaric acid. The outer layer is created by immersion in a cerium (III) nitrate solution containing hydrogen peroxide. It is shown that anodizing in a mixture of sulfuric and tartaric acids prior to the immersion treatment leads to the formation of a thicker and a more uniform cerium-rich layer. The ultramicrotomed sections display the presence of cerium species within the pores of the anodic film. This treatment significantly improves the corrosion resistance of the material.