Structure Of Aluminum Alloys Research Articles

Effect of the laser surface treatment on structure and mechanical properties of AlZn10Si8Mg cast alloy

The laser surface melting/hardening is method which provides increasing mechanical properties of secondary (recycled) Al-Si cast alloys for automotive industry. Improvement of mechanical properties and structure of secondary aluminium alloys can often significantly increase the lifetime of casting and reduce costs for fuel and reduction of environmental loading. Self-hardening Al-alloys (Al-Zn-Si-Mg alloys) introduce an innovative class of light Al-alloys. AlZn10Si8Mg alloy is used for engine and vehicle constructions, hydraulic unit and mould making without the need of heat treatment because this alloy is self-hardened. For this study, a laser beam of Nd: YAG laser, BLS 720, with laser power 50 and 80 W, was used. The final microstructure of Al- alloys depend on the laser process parameters. The laser beam action on the surface of the experimental alloy has changed the microstructure of the material. Melting area is alpha-phase with much fine columnar dendrites morphology without the presence of Si-particles and intermetallic phases. In the transition area, grain refinement of eutectic Si (finer and rounder Si particles) as the modify action of the laser was observed. By increasing the laser power the microhardness of surface layers decreases. In the surface layer (after the 80 W laser beam action), cracks due to uneven heat transfer of the material were observed.

The effect of nickel on shaping the structure of Al-Cu-Mn alloys

This study investigated the effect of nickel on shaping the structure of aluminum alloys of the Al-Cu-Mn type in the “as-cast” condition and after heat treatment according to the T6 procedure. The aluminum alloys of type Al-5%Cu-1%Mn, containing nickel in a range of up to 1.9%, were taken into consideration in this work. Experiments were carried out for thin-walled thickness casting (g = 5 mm) and for reference casting with a wall thickness of g = 35 mm. Metallographic investigations of both the macro- and micro-structure were conducted to estimate the secondary dendrite arm spacing (SDAS), average diameter (dav) of the primary α (Al) grains, and surface fraction of the interdendritic phases (f). Moreover, the degree of dissolution of these interdendritic phases during the solution treatment process was determined. An SEM-EDS analysis was conducted, from which it follows that the addition of nickel at the level of 0.5% changes the un-dissolved particles from a needle-like β-Fe shape to blocky and coagulated. Higher additions of nickel starting from 0.88%) give rise to as many as four phases with higher copper content, the deficit of which results in the smaller strengthening effect of α (Al) dendrites.

Experimental study on the effect of welding parameters and tool pin profiles on the IS:65032 aluminum alloy FSW joints

The friction stir welding (FSW) process was relatively new welding process applied in this research work to join 5mm thick IS:65032 aluminum alloys. IS:65032 aluminum alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio and good corrosion resistance. Compared to the fusion welding processes that are routinely used for joining structural aluminum alloys, friction stir welding (FSW) process is an emerging solid state joining processes in which the material that is being welded does not melt and recast. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. In this investigation, an attempt has been made to understand the effect of rotational speed, welding speed and tool pin profiles on the tensile strength and weld joint efficiencies were studied. Three different tool pin profiles (taper cylindrical,taper triangular and taper square) have been used to fabricate the joints at three different rotational speeds i.e., 1000, 1300 and 1600 rpm and three different welding speeds i.e., 60, 80 and 100 mm/min. The results have been evaluated and compared with each other.

Quantitative Characterization of Hypoeutectic Aluminum–Silicon–Copper As-Cast Alloy Microstructures

Abstract There are only two kinds of qualitative methods for the estimation of aluminum alloy structures: (1) bar charts (degree of eutectic fineness, porosity content, etc.), and (2) atlases of microstructures, mainly for rejection (overheating, for example). In this paper, the development of quantitative methods for the characterization of hypoeutectic Al-Si-Cu as-cast alloy microstructures using panoramic image analysis is described. As-cast and solution-annealed Al-6Si-2Cu alloy microstructures were studied. Parameters for monitoring the quality of the structure of this alloy were proposed. New algorithms for automatic estimation of eutectic fineness and its volume fraction were developed. Correlations among different microstructural parameters were found and interpreted using thermodynamic simulation. The grade of porosity according to GOST 1583-93 versus pore volume fraction, calculated by ASTM E1245, was defined. Bar charts for estimation of the average length of eutectic silicon particles were proposed. The eutectic modification grade, according to the American Foundry Society chart for microstructure control of hypoeutectic alloys, versus both the length and the elongation of eutectic silicon particles was determined. The relationships between alloy hardness and tensile elongation versus the proposed microstructural parameters for Al-6Si-2Cu alloy were defined. These relationships describe various grades of hypoeutectic Al-Si-Cu alloys in both the as-cast and as-solution-annealed conditions.

Tensile Stress Analyses through Digital Image Correlation of Single Lap Joints of High Strength Steel and Aluminum Alloy Using Adhesive Bonding

Structural adhesives methods for joining multi material sheets have been focus of studies and researches for the last years. The most common and widely known type of test is the tensile test of single lap joints (SLJ). However, there are opportunities for analyzing the mechanical performance of such method in SLJ with materials of different properties, such as ductile structural aluminum alloys and high strength steels. It’s also known that the stress state of SLJ, when stressed longitudinally, generates secondary forces. One of them is known as cleavage force which initially leads to the failure of bonded joints. The aim of this work is to analyze the stress state of similar and dissimilar materials SLJ submitted to tensile stresses and also the influence of some variables, such as overlap length, adhesive film thickness and adherend yield limit, over the stress strength of the samples. As adherend materials it was selected the structural aluminum alloy AA 5083 H111 and the high strength steel DP600. At the end of this work it is expected to understand the proper stress state of the SLJ when using similar and dissimilar materials, identifying stress concentrators that bring the structure to fail, using the Digital Image Correlation (DIC) method. It was discovered that the yield strength associated with the overlap length highly influences the SLJ strength, by leading it to a close to pure adhesive shear stress state.

Microstructural features of Sc- and Zr-modified Al-Mg alloys processed by selective laser melting

Selective Laser Melting (SLM) is an additive manufacturing technology that offers significant potential for lightweight applications in space, aerospace, and automotive industries as well as in mechanical engineering. Structural aluminium alloys are therefore of special interest. Scalmalloy® is a scandium-modified Al-Mg alloy which displays exceptional properties when processed by SLM. These properties are predominately related to a generally very fine grained microstructure. However, the fine grained microstructure interspersed with coarser grained regions. Microstructural analyses indicate that the temperature regime and the particle precipitation behaviour are responsible for the duplex grain structures. In melt pool areas close to the pool base, numerous Al3(Sc,Zr), Al-Mg-oxides and mixed particles act as nuclei for Al matrix solidification, leading to the formation of a very fine grained microstructure. In hot melt pool areas with T>800°C the majority of particles dissolve and growth of coarse columnar grains takes place. Better understanding of the formation mechanisms for these two distinct different structures will help pave the way towards newly designed alloy compositions for the SLM process.

Environmentally Assisted Cracking Measurements in Structural Aluminum Alloys Under Accelerated Test Conditions

Environmentally assisted cracking (EAC) of aluminum alloys in corrosive atmospheres is an important maintenance and safety issue for U.S. Department of Defense assets. EAC initiation and propagation of cracks is influenced by the complex interactions of load, environment, and alloy properties. Traditional environmental fracture testing conducted under immersion or constant humidity conditions may produce results that are different than measurements collected under thin electrolyte layers or droplets formed during atmospheric exposure. In addition, most standard methods do not provide instantaneous measures of crack velocity that can be used to identify specific environmental conditions that promote cracking. Improved assessment of EAC susceptibility and the conditions that promote cracking of aluminum alloys has been accomplished with an autonomous, in situ measurement system that can be used in accelerated corrosion test chambers and outdoor exposure sites. Continuous measurements of crack length through...

Finite Element Simulation of Shear Strain during High-Ratio Differential Speed Rolling of Aluminum Alloy 5083

High-ratio differential speed rolling (HRDSR) is a process of severe plastic deformation (SPD) that can be used to improve the structure and properties of aluminum alloys. The mechanism of SPD during HRDSR comes from its large equivalent strain, which is composed of compressive strain and additional shear strain. Plastic strain control of aluminum alloys are of importance for improvement of sheet microstructure and properties. This paper presents the results of the finite element simulation of shear strain during high-ratio differential speed rolling of aluminum alloy 5083. Four deformation routes UD, TD, RD and ND were simulated. By the route UD the sheet was not rotated between two deformation steps, while by the other three cases it was rotated with 180° degrees. By the route RD the rotation axis was the rolling direction, by the route TD the transverse direction and by the route ND the normal direction. The effect of rolls velocity ratio, friction coefficient and deformation route on the shear strain and the effective strain of Al 5083 was found. The results of investigation can be used to optimize the high-ratio differential speed rolling process to improve microstructure and mechanical properties of aluminum sheets.

Finite Element Simulation of Heat Transfer during Cryogenic Asymmetric Sheet Rolling of Aluminum Alloys

Aluminum and its alloys are widely used as structural materials in aerospace, automotive and other industries due to low density and high specific strength. Efficient way to increase strength and other properties of aluminum alloys is to form an ultra fine grain structure using severe plastic deformation methods. Cryogenic asymmetric sheet rolling under liquid nitrogen temperature is a process of severe plastic deformation that can be used to improve the aluminum alloys structure and properties. Prediction of sheet temperature during plastic deformation is very important. The temperature of sheet is changed due to the conversion of mechanical work of deformation into heat through sliding on contact surfaces. This paper presents the results of the finite element simulation of heat transfer during cryogenic asymmetric sheet rolling of aluminum alloy 6061. The effect of thickness reduction, rolling velocity and friction coefficient on the deformation heating and temperature field of aluminum alloy 6061 was found. The results of investigation could be useful for the development of the optimal treatment process of aluminum alloys by cryogenic severe plastic deformation to obtain the ultra fine grain structure and high strength properties.

Influence of Severe Plastic Deformation on Mechanical Properties and Structure of Aluminium Alloys

Influence of Severe Plastic Deformation on Mechanical Properties and Structure of Aluminium Alloys

Welding Distortion Prediction in 5A06 Aluminum Alloy Complex Structure via Inherent Strain Method

Finite element (FE) simulation with inherent deformation is an ideal and practical computational approach for predicting welding stress and distortion in the production of complex aluminum alloy structures. In this study, based on the thermal elasto-plastic analysis, FE models of multi-pass butt welds and T-type fillet welds were investigated to obtain the inherent strain distribution in a 5A06 aluminum alloy cylindrical structure. The angular distortion of the T-type joint was used to investigate the corresponding inherent strain mechanism. Moreover, a custom-designed experimental system was applied to clarify the magnitude of inherent deformation. With the mechanism investigation of welding-induced buckling by FE analysis using inherent deformation, an application for predicting and mitigating the welding buckling in fabrication of complex aluminum alloy structure was developed.

Quasi-static axial crushing experiment study of foam-filled CFRP and aluminum alloy thin-walled structures

Thin-walled aluminum alloy (Al alloy) structure, carbon fiber reinforced plastics (CFRP) tube, aluminum foam (Al foam) and polyurethane foam (PU foam) all can be used as good energy absorbers in automobile, aviation and other industries for their light weight and high energy absorption capacity. In order to clarify the advantages of the design modes, this article studies the crushing behaviors of circular, hexagonal and square CFRP and Al alloy tapered tube and their foam-filled structures subjected to quasi-static axial compression, analyzes and compares the collapse modes and force–displacement curves of these investigated structures as well as calculates the energy absorption (EA) and the specific energy absorption (SEA) of these investigated structures. Experimental results show that the CFRP tapered tubes have higher SEA than that of the Al-alloy tapered tubes and the circular CFRP tubes filled with PU foam have better energy absorption capacity than that of the square and hexagonal structures. In addition, the SEA of the CFRP tube filled with PU foam is 30% higher than that of the Al alloy tube filled with Al foam. Therefore this article leads to a conclusion that PU foam-filled CFRP tapered tube is a potential structure for energy absorber and light weight design.

Vibration influence on structure and density of aluminum alloys

The results of study on aluminum alloys of grade AK9M2 AK12M2 are provided. Alloy crystallization time for alloys AK9M2 AK12M2 decreases, the intensity of reduction depends on the vibration amplitude. For alloys AK9M2 and AK12M2 the optimal amplitude is 2^2.2 mm, allowing a dense cast alloy with a fine grain structure to be obtained. Density of samples from AK12M2, cut from the bottom part, is slightly increases with the rise of the vibration amplitude.

Structure and Properties of High-Strength Aluminum Alloy 1933 Rolled Plates

Results are given for metallographic and x-ray diffraction analysis of the structure, degree of recrystallization, and preferred crystallographic orientations, and also mechanical and corrosion properties through the thickness of 100 mm thick rolled plates of high-strength aluminum alloy 1933, considered in this study as an alternative to forgings.

The Effect of Laser Surface Treatment on Structure and Mechanical Properties Aluminium Alloy ENAC-AlMg9

Abstract In this work, the influence of a high power diode laser surface treatment on the structure and properties of aluminium alloy has been determined. The aim of this study was to improve the mechanical and tribological properties of the surface layer of the aluminium alloy by simultaneously melting and feeding tungsten carbide particles into the molten pool. During the process was used high-power diode laser HPDL. In order to remelt the aluminium alloy surface the HPDL laser of 1.8, 2.0 and 2.2 kW laser beam power has been used. The linear laser scan rate of the beam was set 0.5 cm/s. In order to protect the liquid metal during laser treatment was used argon. As a base material was used aluminium alloy ENAC-AlMg9. To improve the surface mechanical and wear properties of the applied aluminium alloy was used biphasic tungsten carbide WC/W2C. The size of alloying powder was in the range 110-210 µm. The ceramic powder was introduced in the remelting zone by a gravity feeder at a constant rate of 8 g/m.

Will Aluminium Structures Last Forever?

This paper provides an overview of the main issues related to the durability of aluminium alloy structures. In particular, the main corrosion pathways are considered, in relation to alloy type, microstructural features, thermomechanical treatments and environmental characteristics. The strategies for corrosion mitigation are also discussed, with particular focus on the tailoring of anodizing treatments for enhanced durability.

Influence of the Space Orientation of Joints in the Process of Welding on the Strength and Cyclic Crack Resistance of Welded Joints

We study the regularities of influence of the space orientation of a joint (at angles of 0, 30°, 45°, and 90° to the horizontal plane) for different rates of consumable-electrode pulse-arc welding (23, 40, and 57 m/h) of the sheets of AMg5M structural aluminum alloy 4 mm in thickness with the use of a ZvAMg6 filler wire on the physicomechanical properties of welded joints. It is shown that, by varying the heat input into the welded metal and the rate of crystallization of the metal in the bath, we can perform welding without using backing (forming) elements. The optimal characteristics of cyclic crack resistance of the weld metal of these welded joints are obtained in the case of orientation of joints at an angle of 30° to the horizontal plane. The preliminary monitoring of the properties of these welded joints can be performed by the nondestructive eddy-current testing method according to the specific electric conductivity of the metal.

Interacted buckling failure of thin-walled irregular-shaped aluminum alloy column under axial compression

Interacted buckling behaviors and ultimate strength of thin-walled aluminum alloy columns with irregular-shaped cross section were studied using a verified Finite Element Model (FEM). Six interacted buckling failure modes were studied, which were: (1) the interaction of Local bucking and sectional Yielding (LY); (2) the interaction of Local and Global buckling (LG); (3) the interaction of Distortional buckling and sectional Yielding (DY); (4) the interaction of Distortional and Global buckling (DG); (5) the interaction of Local bucking, Distortional bucking and sectional Yielding (LDY or DLY); and (6) the interaction of Local, Distortional and Global buckling (LDG). The load-axial displacement curve, the deflection-axial displacement curve, the development of the axial stress at different positions in the section at mid-span, the out-of-plane displacement at failure along the column length and the axial stress distribution at failure across the section at mid-span were presented. The local buckling and distortional buckling were detected by the turning points on the load-axial displacement curves. The out-of-plane displacement along the column length at failure was used to illustrate the failure mode of the column. Ultimate strengths and failure modes of 174 columns failed by interacted buckling failure modes were investigated by both FEM and current design approaches. For the ultimate strength of the columns under DY failure mode, the results predicted by North American specification for the design of cold-formed steel structural members of American Iron and Steel Institute (AISI) were higher than FEM simulation results. The ultimate strength predicted by American Aluminum Design Manual (AA), Direct Strength Method (DSM), European Code (EN1999) and Chinese Design Specification for Aluminum Alloy Structures (GB50429) were lower than FEM simulation results, no matter what kind of failure modes the column encountered. Mean values of PAA/PFEA, PEC9/PFEA and PGB/PFEA were 0.81, 0.79 and 0.74. DSM could precisely predict the Global buckling (G), LG and DY failure modes. However, for the columns failed by LY, DG, LDY and LDG, they were LG, G, DY and LG when predicted by DSM, respectively. The applicability of DSM to thin-walled aluminum alloy columns with irregular-shaped cross section should be investigated further.

Composite repairs to bridge steels demystified

This paper examines crack growth associated with carbon fibre reinforced plastic (CFRP) repairs to cracked bridge steels and boron epoxy composite and fibre metal patch repairs to cracked aluminium alloy structures. It is first shown that the da/dN versus ΔK curves associated with bridge steels is very similar to that seen in the high strength aerospace steel D6ac. The importance of 1st ply failure, which was first observed on a boron epoxy repair to the F-111 D6ac steel wing pivot fitting, and how to alleviate this failure mechanism is then discussed as is the common design approach whereby after patching the repair is designed to have a ΔK beneath the ASTM long crack threshold ΔKth. It is shown that crack growth in bridge steels repaired with CFRP patches and in aluminium alloy structures repaired with either boron epoxy or glare patches exhibit a near linear relationship between the log of the crack length and the number of cycles. We then show that crack growth in these repairs can be represented by the same simple master curve relationship that has been found to hold for cracks growing in both operational aircraft and full scale fatigue tests. These findings are important since they suggest that the methodology used by the Royal Australian Air Force to certify structural modifications to operational aircraft may also be applicable to composite repairs/modifications to steel bridges, which are generally experience significantly lower stresses.

Effect of Intensive Plastic Deformation on Microstructure and Mechanical Properties of Aluminum Alloys

In work it was studied the influence of intensive plastic deformation on structure and mechanical properties of aluminum alloys. Intensive plastic deformation was carried out by using equal-channel angular extrusion. It is shown that the most efficient angle of intersection of the channels is the angle of Φ=120°, which ensures defect-free parts at the highest possible level of accumulated strain (e=8). It is established that the intensive milling grain structures in aluminum alloys AMG6 and AMC occurs at ECAE-12 passes, while the intersection angle of the channels of 120°. After ECAE-12 in aluminum alloys the grain refinement reaches to the size of ∼⃒1.0-1.5 gm. It is determined that as a result of equal channel angular pressing, the microhardness of alloy AMG6 increases almost 4 times in comparison with the initial state, the microhardness of alloy AMC increases by almost 4.5 times in comparison with the initial state. It is shown that ECAE-12 mass loss is reduced to 5.4 and 5.6 mg, which shows an increase in wear-resistance of aluminum alloys AMG6 and AMC 13-14 %.