Characteristics Of Aluminum Alloys Research Articles

Experimental and finite element study of steady state micro-cutting characteristics of aluminum alloy (2A12)

This paper studies the micro-cutting characteristics of aluminum alloy (2A12) based on a series of orthogonal experiments and finite element method (FEM) simulations. An energy-based ductile failure law was proposed in the FEM simulation. The simulated cutting forces and chip morphology were compared with experimental results. The simulation result indicates that there is a close relationship between the cutting force and cutting heat. The micro-cutting force decreases as the heat flux vector increases. Both the cutting heat and the micro-cutting force need a finite time to achieve a steady state. It is observed that with the cutting speed of 169.95 m/min and uncut chip thickness of 6 μm, the heat flux vector in the workpiece increases to a stable value after 0.06 ms; meanwhile, the principal cutting force decreases to a steady state correspondingly, i.e., the micro-cutting process achieves the steady state. It is concluded that the steady state micro-cutting simulation can reflect the cutting process accurately.

Study on Hydrogen Fluctuations in Aluminum Melt under CAP Process

Hydrogen is the only gas that is appreciably soluble in aluminum and its alloy. Its solubility is small but the effect is significant on the mechanical properties and finishing characteristics of aluminum alloys. In order to remove hydrogen from the aluminum melt and shape intricate castings, a new process, Casting under Adjusted Pressure (CAP for short), was invented. An interesting hydrogen fluctuation phenomenon has been found in the CAP process. The hydrogen concentration within the molten aluminum changes with cyclic vacuuming-pressurizing programs for CAP process. The experimental results indicate that the relative humidity of compressed air exerts a significant influence on the hydrogen concentration of aluminum melt. The hydrogen concentration is maintained between 0.10 and 0.15 ml/100gAl by using compressed air with relative humidity 80-85%. Under the condition of dry compressed air, the hydrogen concentration can be maintained at a level as low as 0.05-0.08 ml/100gAl, which is beneficial to obtain high air-tightness aluminum alloy castings. In addition, the experiment shows that magnesium concentration has no obvious influences on CAP process.

Effect of Material Property Changes on the Performance of Al Rolling Mills

The industrial production of aluminium strip comprises a rather long process chain. One of the characteristics of aluminium alloys is that a number of final strip properties are influenced considerably already at very early process stages. Since it is practically impossible to run large variations of controlled process changes on an industrial mill experimentally, Through Process Modelling (TPM) has been in focus of research and has developed into a valuable tool to design process chains with a view to achieving desired properties. Metallurgical models in combination with (plasto-) mechanical/thermal models trace variables of state through the process chain down to the final operation. However, there are further important properties of the product, which may be generated as consequence of the total production history. Predominant examples are the strip profile and flatness and the product surface. These properties do not only result from the processes settings, they may also have a strong back-effect on the process performance itself. As a consequence they may also affect the metallurgical properties. This paper shows representative computations of in-dustrial aluminium rolling process steps to evaluate the interactions of different mechanisms taking place in the rolling processing chain, with a special attention to profile/flatness, surface and metal-lurgical properties.

Experimental Characteristics of Aluminum Alloys in Dry End Milling

This paper describes the cutting characteristics of aluminum alloys in dry end milling experimentally. The tested materials are A1050, A2017, A2024, A5025 and A7075. The cutter is a flat end mill of Co-cemented High Speed Steel with the diameter of 20 mm. Through the experimental results of side milling, the following three aspects have been found out. Firstly, as to the machining error, A1050 showed smaller machining error than 15 μm in the cutting speed rage from 62.8 m/min to 251.3 m/min. Other Aluminum alloys showed greater values. Secondly, as to the cutting force, those of aluminum alloys except A2017 were generally proportional to their material hardness. The cutting forces of A1050 and A5052 were constant over the whole range of cutting speed. Thirdly, as to the machined surface roughness, A7075 showed the smallest surface roughness among the all materials with its arithmetical mean roughness Ra under 0. 2 µm and with its maximum height of profile Rz under 1 μm. The machined surface roughness of A2017 varied widely. Through the visual inspection of machined surface, A2017 and A2024 showed picked surface as generated by a built-up edge. This document explains and demonstrates how to prepare your camera-ready manuscript for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. The text area for your manuscript must be 17 cm wide and 25 cm high (6.7 and 9.8 inches, resp.). Do not place any text outside this area. Use good quality, white paper of approximately 21 x 29 cm or 8 x 11 inches (please do not change the document setting from A4 to letter). Your manuscript will be reduced by approximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc.

A study of the joint effect of scandium and chromium on the structure and mechanical properties of aluminum and its alloys with magnesium

The kinetics of aging and mechanical properties of aluminum alloys of the Al-Cr-Sc system bearing about 0.4% Sc and up to 0.8% Cr and mechanical properties of alloys of the Al-4.5% Mg-Cr-Sc system with about 0.4% Sc and up to 0.3% Cr are studied. The effect of scandium and chromium additives on the structure and strength characteristics of aluminum alloys is determined. The hardness and the electric resistivity of the alloys are measured in the process of aging at 350°C for up to 64 h.

Ambient Pressure Dependence of Laser-Induced Impulse onto Polyacetal

L ASER ablation can be usefully employed to generate a propulsive impulse on an object not only in the atmosphere but also in vacuum [1–3]. Larson et al. [4] proposed a launch vehicle propelled by repetitively pulsed laser ablation. Several authors [5–9] show that favorable propulsion performance in the atmosphere can be achieved with a polymer material, polyacetal, which is commercially named “Delrin” or is abbreviated as “POM.” The ablated gas from this material does not contain much air pollutant. Targeting space applications, the laser-ablative-propulsion performance of metals and polymers at low ambient pressures has been intensively investigated [10–17]. For many kinds of metals and polymers, Cm ranges from 10 to 100 N-s=J, and depends strongly on the characteristics of the laser pulse. According to measurements byGregg andThomas [10], metallic materials have an optimum laser intensity that maximizes Cm. Phipps et al. [12] formulated experimental Cm characteristics of aluminum alloys and several polymers in terms of the intensity, width, andwavelength of the laser pulse.Cm can be further increased by utilizing the so-called “volume absorber” [13] or layered target [14]. Recent measurements by D’Souza and Ketsdever [17] of Cm for polyacetal at low ambient pressure using a frequency-doubled Nd:YAG pulsed laser showed peak of 110 N-s=J at a laser intensity of the order of 10 W=cm. Several authors investigated the influence of ambient pressure on Cm [18,19]. Pakhomov et al. [18]measured the impulse generated on an aluminum surface irradiated by a CO2 laser pulse whose pulse width was 200 ns; Cm decreased monotonically with decreasing ambient pressure. In Dufresne et al.’s surface-pressure measurement [19], the ambient-pressure dependence of Cm for aluminum was quite sensitive to the laser pulse width. For polymer materials, Beverly and Walters [20] measured the CO2-laser-induced shock pressure in cellulose acetate and polymethylmethacrylate. The peak shock pressures exhibited the complex dependence on the ambient pressure. The ablative impulse dependence of materials other than aluminum warrants further investigations. To quantitatively evaluate the feasibility of laser-ablativepropulsion systems, the propulsive performance of polyacetal over a wide range of ambient pressure needs to be known. In the present paper, the influence of the ambient pressure on the impulse characteristics of polyacetal is investigated experimentally using a transversely excited atmospheric (TEA) CO2 pulse laser.

Determination of flow curves at high strain rates using the electromagnetic forming process and an iterative finite element simulation scheme

The aim of this approach is to determine material characteristics of aluminium alloys at very high strain rates, in the form of a relationship between yield stress, plastic strain and strain rate. To achieve high strain rates up to 10 4 s -1 the electromagnetic forming process (EMF) is applied, where a pulsed magnetic field is used to form materials with a high electrical conductivity in process times between 20μs - 50μs. The forces resulting from the magnetic field and acting on the specimen, which in the considered setup is a tube, can be approximated as a time and location dependent pressure distribution. To compute the associated flow curve array, where the strain rate represents the third dimension, a new method will be proposed that combines an on-line measurement technique with iterative finite element simulations. During the electromagnetic compression of the specimen, the radial displacement of one significant point at the inner tube surface is measured on-line. These measured data are compared to the numerical results during the whole forming process and the deviations will be computed. Based on these differences an automated modification of material data is realised until the experimental data and the numerical solutions fit well. The advantage that EMF is a contactless forming process can be used to determine material characteristics without any influence of friction. Additionally, in contrast to other testing methods the assumption of a mean strain rate over the process time is not needed, because the evaluation is carried out by means of finite element simulations.

Influence of coating thickness and sand fineness on mold filling in the lost foam casting process

The effects of coating thickness and sand fineness on the mold filling characteristics of aluminum alloy 319 have been investigated. Experiments have been conducted with strip patterns and transparent molds have been used to visually record the flow behavior. The results indicate that a higher fill time is observed in thicker coatings and finer sands. Typical flow velocities are on the order of 80 mm/s and 90 mm/s for sands with AFS numbers of 80 and 20 respectively. By comparison, when a completely impermeable mold is used, the flow velocity is reduced to about 20 mm/s. Under normal casting conditions, the gases formed at the metal front are eliminated rapidly into the sand, so that there is no substantial gas layer ahead of the flowing melt. A gas layer may build up at the metal front if the permeability of the mold medium is not adequate and eventually the gas bubbles may escape by penetration through the liquid metal. Factors affecting polymer degradation may have strong effect on mold filling while parameters associated with the elimination of degradation products may control defect formation.

Tribological Behavior of Aluminum Alloys Implanted with Nitrogen, Titanium Then Acetylene

The composition depth profiles, structure and ball-on-disk frictional characteristics of aluminum alloys 2024 plasma-based ion implanted with nitrogen, titanium and nitrogen then acetylene were investigated. The layers implanted with nitrogen then with nitrogen and titanium and finally with acetylene included three zones: a top DLC (diamond-like carbon) zone, a C, Ti and N coexisting intermediate zone which undergoes chemical changes forming TiC, Ti(C,N), TiN, (Ti, Al)N and AlN second phases, and the bottom zone of the substrate. The micro-hardness and nano-hardness of these layers are HK7.8 GPa and 22 GPa, respectively. The layers showed lower friction coefficient and higher wear resistance. The Raman spectra for worn tracks after sliding for different numbers of cycles showed that when the loading was 1 N after sliding 10,000 cycles, a slight graphitization phenomenon of the DLC film is found. If the loading was 20 N, the graphitization phenomenon of the DLC film is more obvious after sliding 2000 cycles. The SEM morphologies of the wear tracks showed that when the load was 1 N, after sliding 7200 cycles the wear is from rubbing and abrasive wear. When the load was 20 N, after sliding 2000 cycles, delamination wear is dominant. Scheduled for Presentation at the 58th Annual Meeting in New York City April 28–May 1, 2003

150 非定常波センシングシステムによるアルミニウム合金の衝撃特性の検討(OS5-4 動的材料変形)(OS5 材料の衝撃強度・損傷に関する最近の知見)

150 非定常波センシングシステムによるアルミニウム合金の衝撃特性の検討(OS5-4 動的材料変形)(OS5 材料の衝撃強度・損傷に関する最近の知見)

Friction and Wear Characteristics of Aluminum Alloy Impregnated Carbon Composite

Pin-on-disk unidirectional sliding friction and wear experiments for an aluminum alloy impregnated carbon composite in contact with a bearing steel were carried out at various levels of contact load in wet and dry air. The aluminum alloy impregnated carbon composite exhibits better friction and wear characteristics than the matrix materials, aluminum alloy and graphite in wet air. The coefficient of friction and wear rate decrease, especially at high loads in wet air. Graphite, together with metallic and oxidative wear particles, adheres to the disk sliding surface of the bearing steel, resulting in the formation of compacted, uniform surface films. The films prevent metal-to-metal contact, achieving a good sliding friction and wear condition.

Metallurgical characteristics of A5083-O aluminium alloy welded by high energy density welding

Summary Since electron beam welding and laser welding have a higher energy density than GTA and GMA welding, both methods allow higher speed welding. The cooling rates estimated in the present research study range between around 500–800°C/sec and around 300–1500°C/sec under the welding conditions respectively adopted in electron beam welding and laser welding. The results of line electron probe microanalysis (EPMA) suggest that magnesium segregates near the dendrite boundaries and that the maximum content tends to decrease from around 14 to 10 mass% as the cooling rate increases. The minimum content at the dendrite cores exhibits the reverse trend. The dissolved amount of magnesium in the weld metal is estimated from the relationship between the lattice parameter and the magnesium content by the X-ray diffraction method. In laser welding, the estimated dissolved amounts of magnesium are around 0.3–0.5 mass% less than in the base metal and tend to increase with an increasing cooling rate. This phenomenon is due to the distribution of magnesium in the dendrites, the dissolved amount becoming almost the same as in the base metal when the weld metal is subjected to homogenising heat treatment. The metallurgical characteristics of aluminium alloy weld metal produced by laser welding are much the same as those produced by electron beam welding, because the cooling rate in the weld metals is much the same.

Mechanical properties and fracture of aluminium casting alloys

This paper treats the mechanical properties and fracture characteristics of aluminium alloys in relation to their microstructure. Microstructural features controlling the mechanical behaviour are discussed emphasising the role of the constituent phases with the aim of drawing attention to the importance of these characteristics with respect to structural integrity. This review concentrates on those microstructural parameters that can alter the resistance to fracture of aluminium alloys. There is extended discussion dealing with the effects of porosity, structure fineness, second phase particles (eutectic–silicon) size, morphology and spacing on the mechanical behaviour and fracture. It also gives the reader information about stages of the fracture process.

Mechanisms governing deformation and damage during elevated-temperature fatigue of an aluminum-magnesium-silicon alloy

The cyclic deformation and fracture characteristics of aluminum alloy 6061 are presented and discussed. The specimens were cyclically deformed using fully reversed tension-compression loading under total strain-amplitude control, over a range of temperatures. The alloy showed evidence of softening to failure at all test temperatures. The degree of softening during fully reversed deformation increased with test temperature. The presence of shearable matrix precipitates results in a microstructure that offers a local decrease in resistance to dislocation movement, causing a progressive loss of strengthening contributions to the matrix. At elevated temperatures, localized oxidation and embrittlement at the grain boundaries are exacerbated by the applied cyclic stress and play an important role in accelerating crack initiation and subsequent crack propagation. The fracture behavior of the alloy is discussed in light of competing influences of intrinsic microstructural effects, deformation characteristics arising from a combination of mechanical and microstructural contributions, cyclic plastic strain amplitude and concomitant response stress, and the test temperature.

Prediction of stable crack growth using continuum damage mechanics

This paper examines the application of uncoupled continuum damage mechanics to the prediction of stable crack growth in engineering materials. The formulation of predictive damage methodology and the implementation into a finite element code is presented. This approach is validated by predicting the crack growth characteristics of engineering alloys using the uniaxial stress-strain curve as the sole source of material parameters. Validation is performed for existing stable crack growth test data for 2219-T87 aluminum alloy. The methodology having been validated, the approach is used to explore the influence of material constraint (e.g., plane stress, plane strain, and axisymmetry) on the crack growth characteristics of aluminum alloys. Thoughts regarding strain coupling are presented.

Effect of Microstructure on the Hot Deformation Characteristics of Aluminium Alloys

Effect of Microstructure on the Hot Deformation Characteristics of Aluminium Alloys

The deformation characteristics of SiC particulate-reinforced aluminium alloy 6061

The deformation characteristics of aluminium alloy 6061 reinforced with particulate SiC have been investigated using experimental and numerical methods. The materials investigated contained 0, 5, 10, 20% by volume and 3, 10, 30 μm by size of SiC particulates. The matrix microstructure was systematically heat treated to natural aged (NA), peak aged (PA) and over-aged (OA) conditions. In order to set up a comparative materials database, the microstructural characteristics of the unreinforced matrix material with identical fabricating and processing history were examined. The tensile strength and stiffness of the composites increased with increasing particle volume fraction for heat treatments provided that it was over a limiting value. The PA specimens had the highest tensile strength, but the NA specimens had the greatest elongation to failure and the largest ratio of tensile to yield strength. Good agreement was obtained between experimental results and model predictions of mechanical properties.

Characteristics of aluminum alloy microplastic deformation in different structural states

The solution to the problem of improving the mechanical properties (including cyclic strength) of structural materials is largely dependent on our knowledge of the laws governing the development of microplastic deformations in them. The effect of heat and mechanical treatment on the elastoplastic properties and fatigue resistance of the commercial aluminum alloys AK4-1 and D16 is analyzed.

Natural aging characteristics of aluminium alloy 6061 reinforced with SiC whiskers and particles

The aging response at room temperature of aluminium alloy 6061 was compared with that of its composites containing SiC whiskers or particles. Materials were solutionized for 2 h at two different temperatures (529 and 557°C), quenched in cold water and naturally aged for up to 90 days. The improvement in mechanical characteristics was checked by means of hardness measurements. The microstructural features of aged samples were studied by differential scanning calorimetry. Both aluminium alloy and its composites showed the same aging sequence. Natural aging resulted in the progressive formation of primitive Guinier-Preston zones. Composites, when solutionized at 529°C, showed different aging kinetics from the aluminium alloy used as a matrix. In fact, in the case of composites such a temperature was not sufficient to allow complete solution of the alloying elements. This resulted in a lower aging rate. On the contrary, composites solutionized at 557°C showed the same kinetic behaviour as alloy 6061. Hence the driving force of the natural aging process depends on the concentration of alloying elements in the supersaturated solid solution only. The high density of dislocations close to the interface between the matrix and the ceramic reinforcement did not accelerate the aging response, contrary to what happens during artificial aging of composite materials.

プラズマ粉体肉盛溶接法によるアルミニウム合金表面への炭化物複合化

Effect of carbide addition on the surface characteristics of aluminum alloy 5083 has been investigated with the plasma transferred arc welding process (DCSP) of NbC, TiC or SiC powder. Optimum overlaying conditions under which bead appearance is superior and porosities in overlaid metal are lesser are determined. Moreover some characteristics of overlaid metal containing carbide are evaluated under these optimum conditions. The results are summarized as follows: (1) The maximum area fraction of carbide in overlaid metal is about 40% for NbC and TiC, and about 30% for SiC, (2) Vickers hardness of overlaid metal containing carbide is in the range between 111 and 141hgf/mm2, (3) Abrasive resistance of overlaid metal at higher sliding speed is remarkably improved by the addition of carbide although that at lower sliding speed is not almost improved, (4) In the 180 degree bend test, cracks appear not in the boundary layer between overlaid and base metals but only in overlaid zone, meaning that the boundary layer is sound enough for ductility.