Mechanical Properties Of Aluminum Alloys Research Articles

Determination of scrap/supply probability curves for the mechanical properties of aluminium alloys in hot extrusion using a neural network-like approach

In this paper a neural network-like approach that accounts for the different uncertainties in the hot extrusion of AA6082 alloys is given. The results, presented in the form of scrap/supply curves, suggest the use of a probabilistic approach in the process of hot extrusion. The proposed approach considers both the epistemic and aleatory uncertainties and takes into account all the available influential input variables. The use of the CAE neural network, which is a special type of probabilistic neural network, is proposed as a powerful tool in the design and partial optimization of the hot-extrusion processes in real, industrial aluminium production. It was found that mechanical properties and the yield can be additionally optimized by reducing the epistemic uncertainties, which consequently requires more accurate measurements and more reliable control of the production processes.

Phase and structure characteristics of recycled AlZn10Si8Mg cast alloy

The contribution describes effect of the temperature (20-400°C) on structure and mechanical properties (Brinell hardness and bending impact toughness) of the recycled AlZn10Si8Mg cast alloy. AlZn10Si8Mg cast alloy are used for engine and vehicle constructions, hydraulic unit and mould making without heat treatment. Improved mechanical properties are strongly dependent upon the morphologies, type and distribution of the phases, which are in turn a function of alloy composition and cooling rate. A combination different analytical techniques (light microscopy upon black-white and colour etching, scanning electron microscopy (SEM) upon deep etching, energy dispersive X-ray analysis (EDX) and HV 0.01 microhardness measurement) were therefore been used for the identification of the various phases. It is therefore necessary to study their structure and impact of intermetallic phases on the mechanical properties of aluminium alloys. The paper evaluates change of absorbed energy of impact at different temperature and the effect of structural change and hardness change in alloy during the test. The experiment was realized out using Charpy hammer and Brinell hardness tester.

Effect of Holding Time Before Solidification on Double-Oxide Film Defects and Mechanical Properties of Aluminum Alloys

Double-oxide films (bifilms) have been held responsible for the variability in mechanical properties of aluminum castings. It has been suggested that the air entrapped inside a bifilm can react with the surrounding melt, leading to its consumption, which might improve the mechanical properties of the castings. In this work the effect of holding the melt before solidification on the distribution of mechanical properties, and by implication on entrained double oxide films, was investigated for several different aluminum alloys. The Weibull moduli of plate castings were determined under tensile conditions, and their fracture surfaces were examined for evidence of oxide films. The results suggested the occurrence of two competing mechanisms during the holding treatment: (1) the consumption of air inside the bifilms by reaction with the surrounding molten metal that may lead to improvements in mechanical properties and (2) the accompanying diffusion of hydrogen into the bifilms, which would be expected to have a deleterious effect on properties.

Modeling of Microporosity Size Distribution in Aluminum Alloy A356

Porosity is one of the most common defects to degrade the mechanical properties of aluminum alloys. Prediction of pore size, therefore, is critical to optimize the quality of castings. Moreover, to the design engineer, knowledge of the inherent pore population in a casting is essential to avoid potential fatigue failure of the component. In this work, the size distribution of the porosity was modeled based on the assumptions that the hydrogen pores are nucleated heterogeneously and that the nucleation site distribution is a Gaussian function of hydrogen supersaturation in the melt. The pore growth is simulated as a hydrogen-diffusion-controlled process, which is driven by the hydrogen concentration gradient at the pore liquid interface. Directionally solidified A356 (Al-7Si-0.3Mg) alloy castings were used to evaluate the predictive capability of the proposed model. The cast pore volume fraction and size distributions were measured using X-ray microtomography (XMT). Comparison of the experimental and simulation results showed that good agreement could be obtained in terms of both porosity fraction and size distribution. The model can effectively evaluate the effect of hydrogen content, heterogeneous pore nucleation population, cooling conditions, and degassing time on microporosity formation.

Effect of deformation and recrystallization conditions on tensile behavior of aluminum alloy 7075

Data on the effect of cold strain and annealing temperature on tensile mechanical properties of aluminum alloy 7075 are presented. The coefficients of linear correlation between the values of hardness, rupture strength, and yield strength are determined for all the tested degrees of cold strain and recrystallization temperatures.

High-temperature mechanical properties of aluminium alloys reinforced with titanium diboride (TiB2) particles

The physical and mechanical properties of metal matrix composites were improved by the addition of reinforcements. The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys (6061 and 7015) at high temperatures were studied. Titanium diboride (TiB2) particles were used as the reinforcement. All the composites were produced by hot extrusion. The tensile properties and fracture characteristics of these materials were investigated at room temperature and at high temperatures to determine their ultimate strength and strain to failure. The fracture surface was analysed by scanning electron microscopy. TiB2 particles provide high stability of the aluminium alloys (6061 and 7015) in the fabrication process. An improvement in the mechanical behaviour was achieved by adding TiB2 particles as reinforcement in both the aluminium alloys. Adding TiB2 particles reduces the ductility of the aluminium alloys but does not change the microscopic mode of failure, and the fracture surface exhibits a ductile appearance with dimples formed by coalescence.

Desarrollo y caracterización de un material compuesto de matriz de aluminio 6061 y partículas de TiB<sub>2</sub>

The incorporation of ceramic particles has been one of the ways developed to improve the mechanical properties of aluminium alloys during the last years. The main objective of this work has been to develop the manufacturing process of the reinforced aluminium alloy and analyse its mechanical properties and microstructure. Details about an innovative MMC manufacturing process and the results obtained in the development of a new family of TiB2- reinforced aluminium alloys for forging and extrusion applications are presented. It has been observed that the considered manufacturing process, consisting in the fabrication of particles by SHS and their incorporation into the selected alloy, is a feasible process to manufacture reinforced alloys that can be subsequently extruded or forged. The final result is the development of a material suitable for extrusion and forging applications and that presents an improvement of fatigue and tensile properties of the matrix alloy.

Nature of reverse anisotropy for aluminum alloy sheets

Reverse anisotropy of the mechanical properties of aluminum alloys containing scandium that causes formation of shear bands during cold rolling is studied. Bands reduce longitudinal properties but have no effect on transverse properties. The possibility of obtaining isotropic sheets without shear bands is discussed.

A combined experimental and finite element approach for determining mechanical properties of aluminium alloys by nanoindentation

Aluminium alloys for the aerospace industry are often clad by roll-bonded aluminium to improve corrosion resistance. The clad layer is of the order of 100 μm in thickness and it is difficult to determine the mechanical properties of this layer by conventional mechanical testing techniques. Nanoindentation is ideally suited to determining the elastic and plastic properties of such layers and here we report on a combined approach using experimental nanoindentation and finite element analysis to extract yield stress and strain hardening exponent for an Al-clad system. The approach used was calibrated against results for an Al 2024-T351 alloy, where conventional mechanical testing data was available. For the Al 2024-T351, a forward analysis was used for extraction of load–displacement curves at different indentation depths with the help of elastic–plastic properties obtained from tensile testing. For a ∼100 μm clad layer of pure aluminium on Al 2024-T351, reverse analysis was used for extraction of elastic–plastic properties from a single indentation test. A yield stress of 110–120 MPa and a value of 0.075–0.1 for the work hardening exponent was obtained for the Al cladding. Nanoindentation properties including maximum load of indentation, contact depth, area of contact and pile-up obtained from the forward and reverse analyses showed excellent agreement with the experimental results.

Sequence effects of twist extrusion and rolling on microstructure and mechanical properties of aluminum alloy 8112

Recently severe plastic deformation processes have been the essence of metal forming researches to produce ultrafine-grained materials. Twist Extrusion (TE) is one of the most unprecedented methods developed in recent years, but remained in laboratory scales. The main reason for this matter refers to some deficiencies like microstructure heterogeneity occurring after TE. However, employing conventional forming techniques could make TE industrial and, moreover, reduce the bulk structure grain size. Using a conventional forming process such as rolling after twist extrusion has been suggested by this paper. T.E process of Al 8112 samples was carried out using a twisted die with 60° die angle and the samples were processed through rolling subsequently. The results demonstrated that implementation of rolling not only reduced heterogeneity but also decreased the grain size and, consequently, enhanced the bulk strength.

Effects of retrogression heating rate on microstructures and mechanical properties of aluminum alloy 7050

The effects of the retrogression heating rate (340 °C/min, 57 °C/min, 4.3 °C/min) on the microstructures and mechanical properties of aluminum alloy 7050 were investigated by means of hardness measurement, tensile properties testing, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that the retrogression heating rate significantly affects the microstructures and mechanical properties of the alloys treated by retrogression and re-aging (RRA) process, and it is found that the medium rate (57 °C/min) leads to the highest mechanical properties. The strengthening phases in the matrix are mainly the fine dispersed η' precipitates and GP zones, and the grain boundary precipitates are coarse and discontinuous η phases.

Electrochemical properties in a seawater environment of 5456-H116 aluminum alloy subjected to optimal friction stir processing

The mechanical properties of aluminum alloy may be enhanced by modifying the microstructure of the metal by friction stir processing (FSP). Previous studies have demonstrated that the mechanical characteristics of 5456-H116 Al alloy subjected to FSP, at 250 rpm and 15 mm min−1 using a full screw probe, are similar to those of the original alloy. In the present work, the same alloy was processed under these optimal conditions, and the range of favorable protection potentials with regard to hydrogen embrittlement and stress corrosion cracking was determined to lie between −1.3 and −0.7 V (versus Ag/AgCl). The electrochemical behavior of the specimens subjected to FSP was superior to that of the original 5456-H116 Al alloy.

Nitriding of 6061T6 aluminium by plasma immersion ion implantation at low energy

It is not easy, in general, to improve the mechanical properties of aluminium alloys by traditional nitriding methods. By contrast, plasma immersion ion implantation (PIII) has been successfully used for hardening and in wear resistance improvement. The present work sets out to investigate the formation of AlN on 6061T6 aluminium samples by the PIII process at low energy (2–6 keV) with ion doses in the order of 10 18 ions/cm 2 and from nitrogen–argon mixtures at different concentrations (N70–Ar30, N50–Ar50 and N30–Ar70) maintained at ∼400 °C sample temperatures. The outcome was evaluated by X-ray diffractometry, scanning electron microscopy, Vickers microhardness tests and profilometry.

Effects of Die Temperature of SSS Die Casting on the Microstructure and Mechanical Properties of ADC12 Aluminum Alloy

In the present paper, the effects of different die temperatures on microstructures and mechanical properties of aluminum alloy ADC12 at Super Slow Speed (SSS) die casting have been investigated, in order to optimize the die-casting process and its parameters. The results show that under SSS experimental condition, the density of castings is higher than that of general die castings. Die temperature has the best value, when the die temperature is 150 °C, smaller dendrites are distributed in the hardened surface layer, and the eutectics structure of and Si changes from needle-like structure into herringbone structure. The properties of the die casting are significantly influenced by the die temperature, the optimum die temperature is 150 °C.

Nitriding of 6061T6 aluminium by plasma immersion ion implantation at low energy

It is not easy, in general, to improve the mechanical properties of aluminium alloys by traditional nitriding methods. By contrast, plasma immersion ion implantation (PIII) has been successfully used for hardening and in wear resistance improvement. The present work sets out to investigate the formation of AlN on 6061T6 aluminium samples by the PIII process at low energy (2–6 keV) with ion doses in the order of 10 18 ions/cm 2 and from nitrogen–argon mixtures at different concentrations (N70–Ar30, N50–Ar50 and N30–Ar70) maintained at ∼400 °C sample temperatures. The outcome was evaluated by X-ray diffractometry, scanning electron microscopy, Vickers microhardness tests and profilometry.

Structure and mechanical properties of aluminum alloy 6061 subjected to equal-channel angular pressing in parallel channels

It is shown that a uniform ultrafine-grained structure in alloy 6061 can be formed already after four cycles of treatment by equal-channel angular pressing in parallel channels (ECAP-PC). Along with grain refinement, in the process of an ECAP-PC treatment there occurs in the alloy a dynamic strain aging, which results in the formation of nanodimensional particles of a strengthening phase Mg2Si. It has been established that the alloy in the UFG state demonstrates a considerably higher level of strength and better plasticity in comparison with the material after a standard strengthening treatment.

Work- and Age-Hardening Behaviour of a Commercial AA7108 Aluminium Alloy

Understanding and prediction of the mechanical properties of aluminium alloys are of great importance with respect to e.g. strength requirements and forming operations. In the 7xxx alloying system several mechanisms influence the hardening behaviour of the alloys, e.g. particle size and distribution, dislocation density, and alloying elements in solid solution. This work is an experimental study of work- and age-hardening considering a commercial AA7108 alloy in the as-cast and homogenized condition. Tensile specimens have been exposed to a solution heat treatment and a two-step age-hardening treatment with varying time at the final temperature. The tensile data for the different tempers have been evaluated in elucidation of already existing models based on the one-parameter framework by Kocks, Mecking, and Estrin. The particle size has been further investigated in the transmission electron microscope for one under- and one over-aged condition and the influence of particles on work-hardening behavior has been discussed.

An investigation on the effect of intensive shearing on the grain refinement of A5754 aluminium alloy

Grain refinement of aluminium alloys has been an established method of improving mechanical properties of aluminium alloys. A5754 wrought aluminium alloy offers a number of attractive superior properties, however, refinement of this alloy and other wrought alloys is still a matter of concern. A novel technique is introduced for the refinement of wrought and cast alloys, using A5754 alloy as a model material. This method not only provides fine and uniform microstructure throughout the products but it also offers possibilities of industrial applications. This technique eliminates the problems associated with chemical grain refinement and introduces physical refinement as a better option for achieving fine grain sizes.

A comparison of continuous SPD processes for improving the mechanical properties of aluminum alloy 6111

Microstructure evolution, mechanical properties, formability, and texture development were determined for AA6111 samples processed by asymmetric rolling (ASR) with different roll friction, velocity, or diameters, conventional rolling (CR), and equal-channel-angular pressing (ECAP). Highly elongated or sheared grain structures were developed during ASR/CR and ECAP, respectively. ASR led to improvedr-values and formability compared with CR primarily as a result of the development of moderate shear-texture components analogous to those developed during ECAP of billet material. ASR based on different roll diameters gave the best combination of strength, ductility, and formability.

Effect of growth restricting factor on grain refinement of aluminum alloys

Grain structure is an important and readily observable feature in aluminum alloy castings. Depending on the constitutional and heat-flow conditions in a solidified aluminum alloy, various morphologies are possible. Grain refining is one of the predominant techniques in controlling the quality of castings. It plays a vital role in improving metallurgical characteristics and mechanical properties of aluminum alloys. Fine equiaxed grains ensure remarkable benefits. There are a number of techniques to achieve fine equiaxed grain structure, but grain refinement by the addition of grain refiners referred to as inoculation is the most popular due to its simplicity. Grain refinement has been studied extensively by researchers for several decades, not only for developing efficient grain refiners but also for achieving an understanding of the mechanism of grain refinement. In spite of its commercial importance, benefits and numerous scientific studies in this area, the grain refinement of aluminum and its alloys is still a controversial subject. Solute elements like titanium segregate to the inoculants/melt interface affecting the dendrites and also affect the constitutional undercooling at the solid–liquid interface. This segregating power of an element is quantified by the growth restricting factor (GRF). In the present investigation, the effect of GRF on grain refinement of aluminum-silicon alloys was studied by the addition of Al-5Ti-1B master alloy. It is evident from this investigation that the growth rate of grains is inversely proportional to the GRF.