Heat-treatable Aluminum Alloys Research Articles

Shoulder Related Temperature Thresholds in FSSW of Aluminium Alloys.

Friction Stir Spot Welding (FSSW) is assumed as an environment-friendly technique, suitable for the spot welding of several materials. Nevertheless, it is consensual that the temperature control during the process is not feasible, since the exact heat generation mechanisms are still unknown. In current work, the heat generation in FSSW of aluminium alloys, was assessed by producing bead-on-plate spot welds using pinless tools. Coated and uncoated tools, with varied diameters and rotational speeds, were tested. Heat treatable (AA2017, AA6082 and AA7075) and non-heat treatable (AA5083) aluminium alloys were welded to assess any possible influence of the base material properties on heat generation. A parametric analysis enabled to establish a relationship between the process parameters and the heat generation. It was found that for rotational speeds higher than 600 rpm, the main process parameter governing the heat generation is the tool diameter. For each tool diameter, a threshold in the welding temperature was identified, which is independent of the rotational speed and of the aluminium alloy being welded. It is demonstrated that, for aluminium alloys, the temperature in FSSW may be controlled using a suitable combination of rotational speed and tool dimensions. The temperature evolution with process parameters was modelled and the model predictions were found to fit satisfactorily the experimental results.

Plastic behavior-dependent weldability of heat-treatable aluminum alloys in friction stir welding

The quality of friction stir welding joints is intimately related to the correct mixing of the stirred material. The material flow is strongly dependent on the plastic behavior of the welded alloy. For this reason, the friction stir weldability depends on the structure, microstructure, and chemical composition of the base material. In this work, in-plane forces and acoustic emission signals were monitored while welding two heat-treatable aluminum alloys. The force evolutions suggested possible continuous and intermittent material flow during friction stir welding depending on the welding parameters. The differences observed in the in-plane forces were corroborated by acoustic emission, confirming the modification in the material flow phenomenology. Therefore, differences observed in aluminum alloys’ friction stir weldability are due to the plastic behavior at high temperature and medium-high strain rate. The higher the deformability of the aluminum alloys, the wider the weldability window in friction stir welding because of continuous material flow in an extended range of process parameters.

Experimental Investigation on Tensile Properties and Yield Strength Modeling of T5 Heat-Treated Counter Pressure Cast A356 Aluminum Alloys

In the present study, experimental investigations on microstructures and tensile properties of an counter-pressure cast (CPC) A356 aluminum alloy under different T5 heat treatment conditions were conducted in the temperature range of 160–200 ∘C for 1–48 h. As the T5 heat treatment time increased, both tensile and yield strength of the CPC A356 alloy either continuously increased at 160 ∘C until 48 h of heat treatment time or increased until the maximum strength values were achieved and then decreased, showing peak aging behavior at 180 and 200 ∘C. Changes in microstructural aspects, such as size and aspect ratio, of the eutectic Si, Mg and Si distribution in the α-Al grain and the stability of intermetallic compounds were found to be negligible during the T5 heat treatments employed in the present study. From high resolution-transmission electron microscope (HR-TEM) analysis, nanosized needle-like β″ precipitates were identified in the specimens, showing a significant increase in strength after the T5 heat treatment. Based on the measured tensile properties and observed microstructure changes, a yield strength model was proposed to predict yield strengths of CPC A356 alloys at arbitrary T5 heat treatment conditions. The calculation results of the model showed good agreement with the experimental data obtained in the present study. From the model calculations, the optimal T5 heat treatment time or temperature conditions were suggested.

Multistep anodization of 7075 – T6 aluminum alloy

This study successfully demonstrated the overall advantages of multistep anodization of heat-treated wrought aluminum alloy AA7075-T6 that is a widely used in aerospace, automotive and fracture-critical applications. The coating properties and morphology are studied in detail for four anodization regimes: a conventional R1 with a constant electric current and R2, R3, R4 with raising the current in two, four and eight steps, respectively. Whereas processes R1 and R2 form coatings with the atomic Al/O ratio of 0.53 that is smaller than 0.67 for oxide Al2O3, R3 and R4 create coatings with the Al/O ratio of 0.83. Due to a higher level of infused oxygen, coatings built in R1 and R2 have burns and powdery appearance, while coatings formed in processes R3 and R4 form exhibit smooth solid-like surfaces. Compared to R1 and R2, R3 and R4 increase the overall growth rate of oxides by 23.4% and 25.6%, respectively, reduce the pore size by 94% and 45% respectively and decrease by 8.4% the amount of a transferred electric charge per one micrometer of the layer thickness. Process R4 creates coatings that are 74.0% more resistant to abrasion, 14.6% harder and 25.4% thicker than coatings formed in R1. As no specialized equipment is required, presented regimes of multistep anodization are well suited for large-scale manufacturing.

Flexural buckling performance of concrete-filled aluminium alloy tubular columns

The use of aluminium alloys as a structural material has recently increased because of their advantageous properties such as high strength-to-weight ratio and corrosion resistance. However, due to their low Modulus of Elasticity, instability is a major concern for aluminium alloy structural members subjected to compression. One of the ways to improve the performance of aluminium alloy hollow sections on this count is to have concrete infill within them. Past research studies have demonstrated the potential of concrete-filled aluminium tubular (CFAT) stub columns and beams to have improved structural performance, but there is still no reported research on CFAT slender columns. This paper presents an experimental and numerical investigation on the structural response of square and rectangular CFAT members under axial compression. A series of 18 tests were carried out, including 9 CFAT and 9 bare aluminium tubular (BAT) columns for reference purpose. The columns had pin-ended boundary conditions allowing rotation about the minor axis. The tubes were made of 6082-T6 heat-treated aluminium alloy and filled with concrete. The experimental failure modes, ultimate strengths and load versus mid-height lateral displacement curves are reported. Finite element models were developed and validated against the test results. A parametric study was subsequently conducted to study the buckling behaviour for a range of cross-sections and concrete strengths. The test and numerical results were utilised to assess Eurocode design equations for Class A aluminium alloy columns. It was shown that the current codified equations underestimate the actual strength of BAT slender columns and a new buckling curve improving the design accuracy is proposed. In absence of design provisions for CFAT columns, the design methodology of European standards for composite steel-concrete members with the material properties of steel replaced by those of aluminium is adopted. Finally, on the basis of the results of this study a design buckling curve suitable for CFAT columns is proposed.

Precipitation-dependent corrosion analysis of heat treatable aluminum alloys via friction stir welding, a review

Although the various advantages of novel Friction stir welding (FSW) process; the weld surfaces are subjected to various serious problems such as lower corrosion resistance, high susceptibility to stress corrosion cracking and poor joint fatigue strength due to complex material flow and severe plastic deformation during the welding process. Corrosion behaviour of friction stir welded (FSWed) precipitate strengthening Al alloys have significant impact on metallurgical and electrochemical properties of structures. In FSW of precipitate strengthening Al alloys the localized heat input and severe plastic deformation creating appreciable changes in microstructure and modifies the microchemistry and metallurgical characteristics of precipitates. The heterogeneous distribution of precipitates and precipitate free zones (PFZs) along the grain boundaries leads to variation in electrochemical behaviour across the weld zones and hence increasing the susceptibility of weld surface to various corrosion attacks such as intergranular corrosion, pitting corrosion, exfoliation corrosion, stress corrosion cracking and galvanic corrosion. However, the corrosion resistance of FSWed joints can be improved either by reducing the size or redissolve the coarsened precipitates within the joint or modifying the microchemistry by controlling the size, location and distribution of precipitates which largely determine the corrosion rate of the weld surfaces. Consequently, it is imperative to address the influence of material modifications during FSW on corrosion behaviour of weld surface. This review paper addresses the precipitate dependent corrosion behaviour of FSWed joints of heat treatable/precipitate strengthening Al alloys and the various effective methods either to reduce or eliminate the effect of corrosion attack in FSWed joints of heat treatable Al alloys.

Microstructure evolution and mechanical properties of low-silicon cast aluminium alloys with varying Mn contents

ABSTRACT The influences of Mn level (0–0.8 wt%) on the microstructure and mechanical properties of as-cast and T6 heat-treated low-silicon cast aluminium alloys were investigated. The results indicated that the addition of 0.5% Mn completely transformed the needle-like β-Fe phase in as-cast condition into a small-sized π-Fe phase, and the π-Fe phase was fully dissolved after T6 heat treatment. The as-cast and T6 heat-treated alloys with 0.5% Mn achieved the best combination of strength and ductility. However, an excess addition of Mn reduced the mechanical properties due to the occurrence of coarse π-Fe phase (as-cast state), α-Al(Fe, Mn)Si phase (T6 heat-treated state) and eutectic Si. With the increase of Mn content from 0 to 0.8%, the fracture modes of the as-cast alloys changed from intergranular + cleavage fracture to intergranular + quasi-cleavage fracture; The fracture modes of the T6 heat-treated alloys underwent a transition from intergranular + cleavage fracture to quasi-cleavage fracture and then to intergranular + cleavage fracture.

Behaviour of Heat Treated Aluminium Alloy under Hardness Test

Currently, Aluminium (Al) 6061 material is used in various industrial application and Automobile sector. Al 6061 gives good formability and excellent mechanical properties. This paper is mainly focused on the behaviour of the heat-treated aluminium alloy-6061 under the various test such as hardness test, impact test and other industrial applications. Based on the outcomes of Heat treatment, the quality of the Aluminium alloy-6061 is also compared with that of Aluminium alloy-5083, 6063. Hence, this paper helps in future research, which is based on the behaviour of the Heat-treated aluminium alloy under Hardness test.

Effects of particulate reinforcements on the hardness, impact and tensile strengths of AA 6061-T6 friction stir weldments

Due to loss of structural strengthening at temperatures beyond 250°C, heat-treated aluminium alloys (e.g. AA 6061-T6) weldments are usually characterized with poor mechanical properties including hardness, tensile and impact strengths. In this work, friction stir weldments of AA 6061-T6 reinforced with the additions of SiC, B4C and Al2O3 particles at the joints were produced and investigated for improved hardness, tensile strength and impact strength over the unreinforced weldment. The results showed that the entire reinforced welded joint exhibited improved hardness because of the enhanced metal matrix grain refinement and inherent high hardness of the reinforcement particles. B4C particle addition produced hardest joint of about 81% of the base metal hardness (∼114 HV0.3). The impact energies of the SiC (16.9 J), B4C (16.5) and Al2O3 (12.2 J) reinforced weldments are closer to that of the base metal (18.6 J) compared with the unreinforced weldment (9.6 J). The reinforced weldments showed no significant improvement over the tensile strength of the unreinforced weldment. B4C and SiC reinforcements produced the highest improvements in the hardness (at the joint) and impact strength of the AA 6061-T6 friction stir weldments, respectively.

Formation of Phases and Microstructures in Al-8Si Alloys with Different Mg Content.

Mg-containing high-silicon aluminum alloy is a heat-treatable aluminum alloy that is now widely used in the aerospace and automotive industries because of its high specific strength, high wear resistance and corrosion resistance, low thermal expansion coefficient, and low cost. More attention has been paid to optimizing the microstructure to increase the performance of this type of aluminum alloy. In the present work, the solidification processes of Mg-free and Mg-containing (0.33–1.32%) Al-8Si alloys were analyzed by the experimental results combined with the thermodynamic calculation. The results showed that α-Al, Si, and Al5FeSi were in the Mg-free Al-8Si alloy ingots, while the Al5FeSi phases in alloys with Mg additions were transformed into π phases (Al8Mg3FeSi6) by the reaction L+Al5FeSi→α-Al+Si+Al8Mg3FeSi6. There was a binary eutectic reaction of L→α-Al+Al5FeSi when the Mg content exceeded 0.51% and the Fe content was higher than 0.17%. With the increase of Mg content, the volume of Mg2Si was gradually increased while the divorced eutectic phenomenon of the quaternary eutectic structure (α-Al+Si+Mg2Si+Al8Mg3FeSi6) was weakened and the eutectic structure was significantly refined.

Aluminium alloy cross-sections under uniaxial bending and compression: A numerical study

The current study numerically investigates the structural behaviour of aluminium alloy square and rectangular hollow cross-sections under compression and uniaxial bending. Material and geometric nonlinear responses were carefully considered within finite element modelling. Geometric imperfections were also included through the execution of an initial eigenvalue buckling analysis. A thorough parametric study was carried out over a range of width-to-thickness ratios used in practice. Different initial loading eccentricities were examined generating various ratios of compressive axial load and bending moment at failure. The relatively new 6082-T6 heat-treated aluminium alloy, which is increasingly employed in structural applications owing to its high strength, was selected for this study. Based on the obtained numerical capacities, the EN 1999-1-1 design interaction curves were assessed providing rather conservative predictions, particularly for the stockiest cross-sections. The simplified Continuous Strength Method was, also, evaluated exhibiting slightly more accurate with less scattering strength provisions.

Numerical study of concrete-filled aluminium alloy tubular columns under eccentric compression

Concrete-filled aluminium tubular (CFAT) columns have numerous benefits, such as aesthetic appearance, less self-weight and good corrosion resistance, over conventional concrete-filled tubular columns. A limited body of research exists for CFAT columns, and the research on the behaviour of CFAT columns under eccentric loading is rather rare. Therefore, the present study aims at investigating the eccentric compressive response of CFAT columns by means of numerical analysis. The numerical models were developed considering nonlinear behaviour of the materials. The models were validated against experimental data obtained from concentric compression tests of CFAT columns. The columns used in the experiments were 6082-T6 heat-treated aluminium alloy square tubes filled with 30 MPa cube strength concrete. The validated models were used to study the influence of different loading eccentricities on the behaviour of CFAT columns. The results are discussed in terms of ultimate strengths and load-lateral displacement responses. A comparison is drawn between the column capacities obtained from the numerical analysis and calculated by European standards. It is found that the design formulae provided in Eurocode are conservative for the eccentrically loaded CFAT columns.

Effect of heat treatment on mechanical properties of forged aluminium alloy AA2219

Aluminum alloy is used in most of the engineering applications. In most of the automotive sector AA2219 alloy is using. It is necessary to study the heat treatment process for improving the strength of material. In this research the effect of heat treatment of aluminum alloy were discussed. AA2219 aluminum alloy was heat treated by age hardening and preheating using Owen. In this result both the process were compared. The mechanical properties tensile strength and elongation % were compared to find an optimal solution. Taguchi is a smart optimization tool for reducing the no of trials. Orthogonal (L9) method is adopted in this research to identify the results. The optimized condition for tensile and elongation percentage revealed that maximum tensile strength at 474.8 MPa and 10.81% elongation. Better properties states that the model is adequate for machining. Scanning electron microscopic images were compared for both heat treated alloy.

Investigation of heat generation during submerged friction stir welding on 6061-T6 aluminum alloy

Friction stir welding (FSW) is a prominent solid state welding process that is widely used to obtain excellent joints in heat-treatable aluminum alloys. Submerged Friction Stir Welding (SFSW) is a new distinction of the popular friction stir welding. The aim of this paper is to study the heat generation (kJ) based on torque in submerged friction welding process on 6061-T6 aluminum alloy. Torque (M) is one of the most significant factors in friction stir welding process because it is directly related to the co-efficient of friction (µ), power (kW) and heat input of the process. In this work, friction stir welding was carried out on aluminium 6061-T6 alloy under normal and submerged conditions at the different rotational speeds (800 rpm, 1000 rpm and 1200 rpm). The water head is also differed from 10 to 20 mm in case of submerged friction stir welding process. Torque (Nm) was measured during the welding while the co-efficient of friction, power (W) and heat generation (kJ) were calculated later.

Material Evolution of Heat-Treated Aluminum Alloy 6101 Quenched in Different Media

The goal of this study was to investigate the changing characteristics of Heat-Treated Aluminum Alloy 6101 quenched in various media. The research methodology of this research includes performing heat treatment on the Aluminum Alloy 6101 samples at various temperatures, specifically 250℃, 350℃ and 450℃ as well as carrying out quenching processes of the samples using Brine and Water as the main quenchants, and then allowing some samples to cool in the furnace and the rest to be normalized in air, after which mechanical tests (hardness and impact test) will then be carried out on the samples, followed by the microstructural analysis of the alloy. The study concluded that Aluminum Alloy 6101 should be heated to 250°C to achieve the greatest positive effect on its hardness properties, and the air was found to be the best cooling medium. It was also established that Brine Solution used as a quenching media has no significant effect on the hardness property of Aluminum Alloy 6101. Furthermore, the findings revealed that 350°C is the best temperature for increasing the Impact Absorbed Energy (IE) and Impact Strength (IS) of Aluminum Alloy 6101, and that cooling in the furnace also increases the IE and IS.

Effects of plasma nitriding on mechanical, tribological and corrosion properties of friction stir welded joints of Al 2024

The Friction stir welding (FSW) is extensively used to connect Aluminium alloys components in space and aircraft industries. Al 2024is heat-treatable aluminium alloy Al 2024has copper as the primary alloying element which has good mechanical strength and fatigue resistance. Its common application is in aircraft for making various components. In this paper, Plasma Nitrided Al 2024 was joined by Friction stir welding at varying RPM and varying welding speed using cylindrical pin tool and experiment was carried out on different samples (without plasma nitriding on both plates with Plasma Nitriding in one plate& without Plasma nitriding on other plate with Plasma Nitriding process on both plates). The effect of Plasma Nitrided surface hardening treatment on the Al 2024 was done to test the tensile strength, impact strength, wear strength and corrosions of FSW welded joints. The result showed that Plasma Nitriding of Al 2024 improved tensile strength, impact strength, wear resistances and corrosion resistances properties of FSW welded joints.

Microstructure and Properties of As-Cast and Heat-Treated 2017A Aluminium Alloy Obtained from Scrap Recycling

The continuous increase in the consumption of aluminium and its alloys has led to an increase in the amount of aluminium scrap. Due to environmental protection, and to reduce the costs of manufacturing aluminum in recent years, a lot of research is devoted to recycling of aluminum alloys. The paper presents the results of research concerning the possibility of manufacturing standardized alloy 2017A from commercial and post-production scrap by continuous casting. Obtained from recycling process ingots were subjected to analysis of chemical composition and intermetallic phase composition. Based on the results of light microscopy (LM), scanning electron microscopy + electron dispersive spectroscopy (SEM + EDS), and X-ray diffraction (XRD) the following phases in the as-cast state were identified: θ-Al2Cu, β-Mg2Si, Al7Cu2Fe, Q-Al4Cu2Mg8Si7, and α-Al15(FeMn)3(SiCu)2. During solution heat treatment most of the primary precipitates of intermetallic phases, like θ-Al2Cu, β-Mg2Si, and Q-Al4Cu2Mg8Si7, were dissolved in the solid solution α-Al, and during natural and artificial aging they precipitate as strengthening phases θ-Al2Cu and Q-Al4Cu2Mg8Si7 with high dispersion. The highest hardness—150.3 HB—of 2017A alloy was obtained after solution heat treatment from 510 °C and aging at 175 °C. In the static tensile test the mechanical (Rm and Rp0.2) and plastic (A5) properties were determined for 2017A alloy in the cast state and after T4 heat treatment. The highest strength properties—tensile strength Rm = 450.5 MPa and yield strength R0.2 = 268.7 MPa with good relative elongation A5 = 14.65%, were obtained after solution heat treatment at 510 °C/6 h/water quenching and natural aging at 25 °C for 70 h. The alloy manufactured from recycled scrap is characterized by relatively high mechanical properties.

Mechanical Properties and Microstructural Characterization of Dissimilar Friction Stir Welded AA5083 and AA6061 Aluminium Alloys

Solidification is one of the major issues that was faced during the fusion welding of dissimilar non-heat treatable and heat treatable aluminium alloys. To overcome this issue Friction Stir Welding played a very vital role, since it is a solid state welding process. In the current study, dissimilar friction stir welding was carried out between non heat-treatable aluminium alloy AA5083-H111 and heat-treatable aluminium alloy AA6061-T6. The microstructural analysis and the mechanical properties of the dissimilar friction stir welded aluminium alloy AA5083-H111 and AA6061-T6 have been investigated. Both optical microscopy and scanning electron microscopy was used to evaluate the microstructural features. The elemental analysis was carried out using SEM-EDX. The tensile properties are studied using Universal Testing Machine. Hardness at various zones of the welded joints was measured using Vicker’s Hardness Testing Machine. The mechanical properties of the friction stir welded joints were correlated with the microstructure of the dissimilar welded joints.

Influence of rotational speed on the dissimilar friction welding of heat-treated aluminum alloys

Union of dissimilar alloys by means of welding processes is often challenging than union of like material or alloys. The trivial distinction in mechanical, metallurgical and formation of alloys lead in major changes in the welded joints. Friction welding can be implemented effectively to unite a much wide variety of dissimilar materials. It efficiently resolves so many complex issues in front of contemporary manufacturing, like recuperating quality, dipping costs and safeguarding the environs. It produces the high strength joints compared to fusion welding process. The properties of the welded joints contingent on the right assortment of the welding parameters. In this investigation, the effect of rotational speed on mechanical properties was assessed by tensile, microhardness tests and weld flash appearance of friction welded joint of aluminium alloy 6063-O and aluminium alloy 6063-T6.

A NEW AND RELIABLE STATISTICAL APPROACH WITH EFFECTIVE PROFILING OF HARDNESS PRESERVING SAMPLES IN TIG-WELDING, THERMAL TREATMENT AND AGE-HARDENING OF ALUMINUM ALLOY 6061

Light metals and alloys are highly fascinated by aircraft industries due to their good strength-to-weight ratio, which is the prime requirement for aviation’s designers. Assembling of aircrafts components is often carried out using tungsten inert gas (TIG) welding, which is more acceptable for heat treatable aluminum alloys. We focus on the viable use of TIG welded assemblies of 6061 aluminum alloys to homogenize its hardness properties by heat treatment. Investigation proceeds by perceiving the effect of different precipitation hardening conditions on Aluminum alloy through their micro and macro-structural behavior and microhardness analysis. The statistical examination was conducted to evaluate the integrity of heat treated samples. A new and efficient measure – the coefficient of reliability – is introduced to outline the best hardness preserving samples. The statistical analysis shows the effectiveness of the coefficient of reliability to outline the best samples. The experimental results show that the samples aged at 175oC for 12 hours preserve the hardness profile of the welded alloy. The result is also verified from the mean hardness, coefficient of reliability and standard deviation values and in agreement with literature.