Aluminum Clad Research Articles

Iconic Campus of the Zayed University Abu Dhabi

AbstractThe Emirate of Abu Dhabi is planning for the post‐oil era, so education plays a central role in its Master Plan 2030. The new building complex of the Zayed University, intended for 6,000 students, is located in the future Capital District directly on the important connecting road between the Abu Dhabi international airport and the old town peninsular.Hamburg architects BRT’s (Bothe Richter Teherani) symbolism‐rich design moulds the 100.000 m2 GFA ensemble of buildings in the central area into a huge sculpture. The linking element is a jointless free‐form roof of 8,000 tonnes of steel with aluminium cladding whose shape and lightness echoes the traditional Arabic chador.A very short time for design and construction required close cooperation within the international team set up by a main contractor. The project required mastering of numerous engineering challenges, different design philosophies, difficult interfaces between design and construction works on a huge construction site with up to 8,000 workers running in parallel to the design works.

Cover Picture: Steel Construction 2/2012

AbstractThe Emirate of Abu Dhabi is planning for the post‐oil era, so education plays a central role in its Master Plan 2030. The new building complex of the Zayed University, intended for 6,000 students, is located in the future Capital District directly on the important connecting road between the international airport Abu Dhabi and the peninsular old town. Hamburg architects BRT Bothe Richter Teherani symbolism‐rich design moulds the 100.000 m2 GFA ensemble of buildings in the central area into a huge sculpture. The linking element is a jointless free‐form roof of 8,000 t of steel with aluminum cladding whose shape and lightness echoes the traditional Arabic chador, pp. 108‐116. (Photo: Al Habtoor

Investigation on friction stir lap welding of aluminium to aluminium clad steel sheets

In this work, the feasibility of friction stir lap welding an aluminium alloy (Al-5083) to the aluminium clad steel sheet was studied. The welded joints were characterised by various methods including shear–tensile test and optical microscopy and scanning electron microscopy. The results indicated that sound and defect free joints were obtained. The fracture loads of the samples reached up to 94% compared with that of the steel base metal. Moreover, the joint strength linearly increased with the decrease in thickness of the aluminium layer roll bonded on the steel sheet. It was also shown that welding rotation and travel speed variation did not considerably impact the fracture loads in the studied range.

Application of Fractal Geometry to the Problems of Prediction of the Residual Service Life of Aircraft Structures

The deformation pattern of the surface of clad aluminum alloys is regarded as an indicator of the degree of accumulated fatigue damage. We demonstrate the possibility of application of the methods of fractal geometry to the analysis of the optical images of deformation patterns. We study a series of procedures used for the calculation of fractal dimensions and propose their complex application to the problems of prediction of the residual service life of aircraft structures according to the state of the deformation pattern.

Nanoporous Waveguide Sensor with Optimized Nanoarchitectures for Highly Sensitive Label-Free Biosensing

Label-free optical biosensors have attracted much attention, and nanoporous metal-oxide membranes with uniform pore structure and diameter are promising candidates for platforms of label-free optical biosensors. However, development of such sensors with high sensitivity still remains challenging. In this paper, we report on the remarkably enhanced sensitivity of a label-free nanoporous optical waveguide (NPWG) sensor composed of a porous anodic alumina (PAA) waveguiding film and an aluminum cladding film. The enhanced sensitivity was achieved by engineering nanostructures and tuning optical properties of the PAA film. Careful tuning of the porosity, pore density, thickness, and refractive index of the PAA film could significantly improve the sensitivity of the NPWG sensor toward adsorption of bovine serum albumin (BSA) onto the PAA surface, and the optimized sensor responded to the adsorption of BSA with an extraordinarily large red shift (>300 nm) of a waveguide mode due to the large adsorption capacity of the PAA film and the inherently high sensitivity of the waveguide mode. The Fresnel calculations suggested that the potential sensitivity of the NPWG sensor was much higher than that of the conventional surface plasmon resonance (SPR) sensors.

Corrosion Protection of Light Alloys Using Low Pressure Cold Spray

Corrosion attack of aluminum- and magnesium-based alloys is a major issue worldwide. This study provides a report on the electrochemical behavior of several types of protective metal coatings obtained by low pressure cold spray (LPCS) and describes the performance of the latter’s corrosion resistance properties. In this manner several metal feedstock compositions were cold sprayed on AA2024-T3 Alclad substrate. Electrochemical methods, such as open circuit potential and potentiodynamic polarization, were used in combination with materials characterization techniques to assess the performance of LPCS protective coating layers. All sprayed samples were tested in the accelerated corrosion salt spray chamber for a time period of up to 500 h to obtain corrosion kinetics data, and with specific attention being focused on the characterization of the coating’s microstructural and mechanical properties. The overall conclusion of this study is that the LPCS process could be utilized to deposit corrosion protection coatings of light alloys as well as to repair aluminum and aluminum cladding structures during overhaul maintenance schedule in industry.

Effects of annealing process on interface and mechanical properties of silver clad aluminum wires

The billet was prepared by putting the aluminum bar into the silver tube, and the silver clad aluminum wire was fabricated through cold hydrostatic extrusion and subsequent drawing. The effects of annealing parameters on the interface and properties of the wires were investigated. The results showed that when the annealing temperature was below 150°C and annealing time was less than 30min, no new phase was observed obviously, while new phase could be observed when the temperature reached above 200°C. The results of energy spectrum analysis showed that new phase were mainly Ag3Al electronic compound (μ phase) which was hard brittle phase with the β-Mn structure. The effects of annealing temperature and time on the interface were different: for any annealing time in this study, the width of the interface rose markedly with the increase of annealing temperature, while annealing time had no significant effect on the width of interface when the temperature was low. Only when the temperature was comparatively high, the increment rate of width of the interface gradually increased with the rise of annealing time. The width of interfaces was 5∼7μm, 7∼9μm and 10∼12μm after annealing treatment under the temperature of 150°C, 200°C and 300°C respectively for 30minutes. If the annealing temperature was lower than 200°C, the main way was that silver diffused towards aluminum, but when the annealing temperature was up to 300°C, the reverse diffusion occurred. When annealing temperature was 150°C or 200°C, the tensile strength of composite wire decreased after increased with the increment of annealing time, while when it was 300°C, the tensile strength always increased. The elongation percentage of composite wire had an adverse change compared to that of tensile strength. The reason for the change of mechanical properties of composite wire is mainly that mechanical properties was synthetically influenced by three mechanisms called annealing softening, diffusion phase transformation of interface and alloying of sheath and core because of their interdiffusion. Annealing softening produced dominant effect in lower annealing temperature and shorter annealing time condition, while the other two mechanisms had main effect in higher annealing temperature and longer annealing time condition.

Theoretical Account for the Bimetallic Bonding of the Copper Clad Aluminum Wire by Clad-Drawing at Room Temperature

By analysis of the theoretical calculation, it is obvious that the bimetallic bonding of the copper clad aluminum wire by clad drawing at room temperature is the action results of collective gravitation of a great lot of two metal surface atoms reciprocally by outside force. The interatomic potential energy of the closer atoms of two metal surfaces is obvious lower, so as to change for electron within the distance. The interdiffusion of the bimetallic surface atoms by clad drawing at room temperature, is good for improving the bond strength, but is not necessary.

Recovery Behaviour at the Inter-Alloy Region of a Cold Rolled Clad Aluminum Alloy

This study examines the recovery behaviour of the inter-alloy region between a core AA6XXX clad with AA3003 after 72% rolling reduction. Sample coupons were heated isochronally or isothermally, at different temperatures or times, respectively, to probe the recovery kinetics of x-ray peak broadening, x-ray macro-texture, and micro-hardness from the cold rolled state. The inter-alloy region had a strong β-fibre typical of rolled Al. The recovery of the {220} and {311} x-ray line profiles were observed between anneals. The full width half maximum was determined from a pseudo-Voigt fit of the profiles to obtain the defect-related information. Distinct changes in the peak shape and microhardness were observed above 80°C (start of recovery), which goes on all the way to 300°C due to recovery, and beyond 300°C both hardness and peak width drop rapidly (recrystallization start), the latter behaviour being closer to AA3004. Modified Williamson-Hall analysis confirms that recovery is due to dislocation annihilation.

Effect of primary cladding on properties of alumina nanocrystal coating during hard anodising

The aim of the present paper is to investigate the effects of aluminium matrix composition and existence of primary cladding over the 2024 aluminium alloy on the cover layer properties during hard anodising. Three types of aluminium with different chemical compositions were selected and anodising process was done. X-ray studies showed that the generated coating crystals are at nanometre scale and this phenomenon was confirmed by TEM. The sample with primary cladding has the best hardness characteristic and wear resistance while because of some defects, 2024 aluminium alloy has the lowest qualities among other samples. Furthermore, from the aspect of energy, the primary clad aluminium was the most economical.

Interfacial Microstructure and Bonding Strength of Copper Cladding Aluminum Rods Fabricated by Horizontal Core-Filling Continuous Casting

Copper cladding aluminum (CCA) rods with a diameter of 30 mm and a sheath thickness of 3 mm were fabricated by horizontal core-filling continuous casting (HCFC) technology. The microstructure and morphology, distribution of chemical components, and phase composition of the interface between Cu and Al were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive spectrometer (EDS). The formation mechanism of the interface and the effects of key processing parameters, e.g., aluminum casting temperature, secondary cooling intensity, and mean withdrawing speed on the interfacial microstructure and bonding strength were investigated. The results show that the CCA rod has a multilayered interface, which is composed of three sublayers—sublayer I is Cu9Al4 layer, sublayer II is CuAl2 layer, and sublayer III is composed of α-Al/CuAl2 pseudo eutectic. The thickness of sublayer III, which occupies 92 to 99 pct of the total thickness of the interface, is much larger than the thicknesses of sublayers I and II. However, the interfacial bonding strength is dominated by the thicknesses of sublayers I and II; i.e., the bonding strength decreases with the rise of the thicknesses of sublayers I and II. When raising the aluminum casting temperature, the total thickness of the interface increases while the thicknesses of sublayers I and II decrease and the bonding strength increases. Either augmenting the secondary cooling intensity or increasing the mean withdrawing speed results in the decrease in both total thickness of the interface and the thicknesses of sublayers I and II, and an increase in the interfacial bonding strength. The CCA rod with the largest interfacial bonding strength of 67.9 ± 0.5 MPa was fabricated under such processing parameters as copper casting temperature 1503 K (1230 °C), aluminum casting temperature 1063 K (790 °C), primary cooling water flux 600 L/h, secondary cooling water flux 700 L/h, and mean withdrawing speed 87 mm/min. The total thickness of the interface of the CCA rod fabricated under the preceding processing parameters is about 75 μm, while the thicknesses of sublayers I and II are about 1.1 and 0.1 μm, respectively.

The Effect of Aluminum Clad on the Electrochemical Properties of the Similar Weld of Friction-Stir Welding of 2524

Microstructures, static weight loss and potentiodynamic polarization curves were carried out on the Friction-stir welds of Al clad 2524 alloy with the thickness of 1.35 mm. The results indicated that the microstructures of the Nugget had been remarkably reshaped. A dynamical recrystallization took place on the zone of the weld nugget and an equiaxed grain structure formed. The static weight loss and potentiodynamic polarization curves results indicated that the resistance of corrosion of the base material (with aluminum clad) was superior to that of its weld, but the anti-corrosive ability of the weld was superior to that of the base material without aluminum clad.

Application of a strip-yield model to predict crack growth under variable-amplitude and spectrum loading – Part 2: Middle-crack-tension specimens

In previous work, fatigue-crack-growth tests were conducted on middle-crack tension, M( T), and compact, C( T), specimens made from the same D16Cz (clad) aluminum alloy sheet. These tests were conducted over a wide range of stress ratios ( R = P min/ P max = −0.5 to 0.75) to generate crack-growth-rate data from threshold to near fracture. These tests were used to generate the effective stress-intensity factor range (Δ K eff ) against rate curve using a crack-closure model. The analyses collapsed the rate data from both specimen types into a fairly narrow band over many orders of magnitude in rates using proper constraint factors. Constraint factors were established from single-spike overload and the constant-amplitude tests. Herein, the life-prediction code, FASTRAN, which is based on the strip-yield model concept, was used to calculate the crack-length-against-cycles under constant-amplitude (CA) loading and the single-spike overload (OL) tests; and to predict crack growth under variable-amplitude (VA) loading and simulated aircraft loading spectrum tests on the M( T) specimens. The calculated crack-growth lives under CA and an OL tests were generally within ±20% of the test results, but slower crack growth under the double-shear fatigue mode, rather than single shear, may be the reason for some of the larger differences. The predicted crack-growth lives for the VA and Mini-Falstaff spectrum tests were also short by 25–45%. A modified model with some assumed notch constraint effects matched the spectrum tests quite well. Issues on the crack-starter-notch effects under spectrum loading are discussed, and recommendations are suggested on avoiding these notch effects.

Application of a strip-yield model to predict crack growth under variable-amplitude and spectrum loading – Part 1: Compact specimens

Fatigue-crack-growth tests were conducted on compact, C( T), specimens made of D16Cz (clad) aluminum alloy under constant-amplitude loading, a single spike overload, and simulated aircraft spectrum loading. Constant-amplitude tests were conducted to generate crack-growth-rate data from threshold to near fracture over a wide range of stress ratios ( R = P min/ P max = 0.1–0.75) using the new compression pre-cracking test methods. Comparisons were made between test data generated on the C( T) specimens with test data from the literature on middle-crack-tension, M( T), specimens machined from the same sheet. A crack-closure analysis was used to collapse the rate data from both specimen types into a narrow band over many orders of magnitude in rates using proper constraint factors. The constraint factors were established from constant-amplitude (CA) and single-spike overload tests. The life-prediction code, FASTRAN, which is based on the strip-yield model concept, was used to calculate crack-length-against-cycles under CA loading and a single-spike overload (OL) test, and to predict crack growth under simulated aircraft spectrum loading tests on C( T) specimens. The calculated crack-growth lives under CA loading were generally within about ±25% of the test results, but slower crack growth under the double-shear fatigue mode, unlike the single-shear mode (45 o slant crack growth), may be the reason for some of the larger differences. The predicted results under the single-spike overload and the Mini-Falstaff+ spectrum were within 10% of the test data.

Effect of Melt Treatment on Forming and Brazing Characteristics of 4343/3003/4343 Aluminum Clad Sheet

In this study, it was aimed to investigate the effects of grain refining of 3003 core alloy on forming and brazing characteristics of 4343/3003/4343 aluminum clad sheet. Ti inoculation level was changed up to 0.1wt% by adding Al-10Ti master alloy into 3003 aluminum melt as grain refiner. The three-layer aluminum clad sheets of 0.7 mm thickness were fabricated by hot roll bonding process. The forming and brazing characteristics were evaluated by measuring FLD (forming limit diagram), bonding strength and sagging resistance.

Comparison of liquid impingement results from whirling arm and water-jet rain erosion test facilities

► Correlation of whirling arm and water-jet erosion test rigs. ► Use of roughness measurements as a method to compare high velocity liquid impact tests. ► Development of a laboratory scale whirling arm rain erosion test rig. ► Inspection of eroded surfaces by scanning electron, confocal and optical microscopy. A laboratory-scale Whirling Arm Rain Erosion test Rig (WARER) has been designed, developed and commissioned at the University of Limerick. The facility is capable of impact speeds of 178 ms −1 and a rainfall rate of 25.4 mm h −1 . Circular samples of 27 mm diameter (nominal) and a maximum thickness of 2 mm can be accommodated. The facility was developed to test the resistance of leading edge aircraft materials to the repeated impact of rain droplets in flight. A challenging feature of the design was to enclose the whirling arm within a chamber so that it could be operated in an open-plan laboratory. A design problem that arose was the effect of aerodynamic heating of the air within the chamber. This led to a warming of the water and consequently a change in the droplet formation, which in turn caused problems relating to the repeatability of the tests. A cooling system was thus incorporated to keep the temperature of the water droplets below the established threshold of 20 °C. Calibration testing has been undertaken by conducting back-on-back testing of samples with a previously developed water-jet facility at EADS IW, Munich. This Pulsating Jet Erosion Test rig (PJET) is capable of 225 ms −1 droplet speed. Multiple impacts are produced on the sample at numerous locations, each location having an increased number of impacts. The impact frequency is equivalent of 25 mm h −1 rain fall. Clad aluminium alloy (AA2024-T3) was used with the soft AA1230 clad layer being removed during testing. Post impact evaluations were carried out using Confocal Laser Scanning Microscopy (CLSM) and surface roughness measurements. A cumulative erosion-time curve was produced from the WARER samples.

Resumption of JRR-4 and characteristics of neutron beam for BNCT

The clinical trials of Boron Neutron Capture Therapy (BNCT) have been conducted using Japan Research Reactor No. 4 (JRR-4) at Japan Atomic Energy Agency (JAEA). On December 28th, 2007, a crack of a graphite reflector in the reactor core was found on the weld of the aluminum cladding. For this reason, specifications of graphite reflectors were renewed; dimensions of the graphite were reduced and gaps of water were increased. All existing graphite reflectors of JRR-4 were replaced by new graphite reflectors. In February 2010 the resumption of JRR-4 was carried out with new graphite reflectors. We measured the characteristics of neutron beam at the JRR-4 Neutron Beam Facility. A cylindrical water phantom of 18.6 cm diameter and 24 cm depth was set in front of the beam port with 1cm gap. TLDs and gold wires were inserted within the phantom when the phantom was irradiated. The results of the measured thermal neutron flux and the gamma dose in water were compared with that of MCNP calculation. The neutron energy spectrum of the calculation model with new reflector had little variation compared to that with old reflector, but intensities of the neutron flux and gamma dose with new reflector were rather smaller than those with old reflector. The calculated results showed the same tendency as that of the experimental results. Therefore, the clinical trials of BNCT in JRR-4 could be restarted.

Investigation on the bond strength of Al-1100/St-12 roll bonded sheets, optimization and characterization

Al-1100/St-12 aluminum clad steel sheets were produced using roll bonding process at different reductions in thickness and with various supplemental annealing treatments. Experiments were conducted by applying the Taguchi method to obtain optimum condition for maximizing the joint strength. The joint strengths of the bi-layer sheets were evaluated by peel test. The Al/Fe intermetallic phases at the joint interface and the peeled surfaces were examined using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) and Vickers microhardness test were performed to characterize the intermetallic compounds. The results indicate that at the optimum condition of 0.50 reduction in thickness, 450 °C annealing temperature and 90 min annealing time, the bond strength reaches to the base aluminum sheet strength. In comparison to the reduction in thickness and annealing time, the annealing temperature has the most influence on the joint strength changes. In general, raising the annealing temperature up to 450 °C, increases the joint strength. However, annealing treatment at 500 °C reduces the strength due to the formation of brittle Al/Fe intermetallic layer at the bond interface. Additionally, increasing the reduction in thickness improves the joint strength.

A New Technology for Producing Bimetal Rods

This paper studied a new technology for producing copper cladding aluminium robs. The Horizontal Core-filling Casting equipments for producing copper clad aluminium rod were designed, and the interfacial compounds and the primary phase were analysized by backscattered electron image and electron probe micro-analyzer, and X-ray diffraction unit. The results showed that middle seam region was white eutectic microstructure and a-Al structure, where the eutectic takes on chrysanthemum distribution and the sharp or the edge of chrysanthemum was CuAl2. The dark region in the middle seam region was a-Al.

The Property Research on High-entropy Alloy AlxFeCoNiCuCr Coating by Laser Cladding

High-entropy alloys have been found to have novel microstructures and unique properties. The main method of manufacturing is vacuum arc remelting. As in situ cladding laser cladding has capability of achieving a controllable dilution ratio, fabricating highentropy alloy by laser cladding is of great significance and potential for extensive use. In this study, a novel AlxFeCoNiCuCr high-entropy alloy system was manufactured as the thin layer of the substrate by laser cladding; also high temperature hardness, abrasion performance, corrosion nature of the AlxFeCoNiCuCr high-entropy alloy were tested under the different ratio of aluminum. This study shows higher aluminum clad exhibit higher hardness, better abrasion resistance and corrosion resistance.