Microstructure Of Aluminum Alloy Research Articles

Effect of Pressure on Microstructure and Cooling Curves of A356 Aluminum Alloy During Solidification

During solidification process of metals and alloys in die casting, the cooling rate of molten material and also freezing time are affected by the heat transfer coefficient of metal/mold interface which is not constant at whole casting time. Therefore, determination of the cooling curves and the heat transfer coefficient is a crucial step in optimization of casting process by simulation because the resultant microstructure of cast components is affected by cooling rate. In the present study, the effect of applied pressure on cooling curves and microstructures of A356 aluminum alloy was investigated using a specially designed apparatus. Results showed that the cooling curves obtained from the central axis of cylindrical sample clearly represent the solidus and liquidus temperatures which can be used for determination of freezing time. It was observed that the solidification time decreases with increasing applied pressure. Also, the side thermocouples showed a temperature drop at the moment of applying pressure in which its magnitude increases with the increase in applied pressure. Moreover, the metallographic examinations showed that the microstructure of as-cast samples is refined with the increase in pressure. Also, the heat transfer coefficient obtained from experiments was used in the simulation of casting process and the simulated cooling curves were matched carefully with the experimental curves.

Texture and microstructure evolution of A390 aluminum alloy during ECAP

The current work focused on the effect of equal channel angular pressing (ECAP) process on microstructure and texture evolution of A390 aluminum alloy. The alloy successfully processed up to four ECAP passes in route A at 400 °C. The ECAP die, has a circular cross-section channel with a diameter of 12 mm, an inner corner angle, ϕ, of 110° and an outer corner angle, Ψ, of 70°. The microstructural observation and macro-texture from ED–TD plane characterized by optical microscopy (OM) and x-ray diffraction (XRD). Microstructural observation revealed the extensive grain refinement of the aluminum matrix and second phase particles fragmentation were obtained after the first two ECAP passes. In addition, the particle stimulated nucleation (PSN) mechanism activated during the first pass. The variations of fiber textures such as C, A, B and A*1Ѳ and ideal simple shear textures such as {111}〈110〉, {112}〈110〉, {100}〈110〉, and {111}〈112〉 components were evaluated in both sides of samples. The results showed that the ECAP process developed the {001}〈310〉 component and weakened the {100}〈001〉 and {011}〈100〉 components. Three new components including {113}〈121〉, {021}〈112〉, and {221}〈012〉 created during ECAP process.

Fracture behaviour of laser-welded 2219-T6 aluminium alloy under pulsed Lorentz force

Electromagnetic forming is a high-speed forming technology, using pulsed Lorentz force to make sheet metal deformed. The fracture behaviour of material during electromagnetic forming is a significant scientific issue in the development of this technology. In the current work, experimental methods are used to investigate the properties and microstructure of laser-welded 2219-T6 aluminium alloy and the fracture behaviour of the weld joint under pulsed Lorentz force. The results indicate that the hardness, strength, ductility, impact toughness of the laser-welded joint are all worse than that of the base metal because of the inhomogeneity of the microstructure and the existence of coarse brittle eutectic phases. This leads to the ductile fracture of laser-welded joint at the initial stage, followed by the sparking and partially melting breaking phenomena, under the pulsed Lorentz force. The molten structure is also observed on the fracture surface of the weld joint after electromagnetic tensile test rather than mechanical high-speed tensile test. During the fracture process under pulsed Lorentz force, local short circuits occur at the ductile crack tip of the weld joint due to the eddy current effect, resulting in the melting of the weld metal. The percentage reduction of area and the dimple sizes in the fracture morphology of the specimen under the conditions of high-speed deformation are larger than that under the condition of quasi-static tensile test, indicating the slight improvement in ductility of the laser-welded joint under high-speed deformation due to the inertial effect and the adiabatic temperature rise from the plastic work. Particularly, the above indicators are even larger under electromagnetic tensile test, revealing extra very slight increase in ductility compared with mechanical high-speed tensile test because of the body force and the additional temperature rise resulting from the Joule heat.

Revealing the evolution of microstructure, mechanical property and corrosion behavior of 7A46 aluminum alloy with different ageing treatment

Mechanical property and corrosion behavior of 7A46 aluminum alloy under peak-ageing (T6), double-ageing (DA) and pre-ageing (PA) followed by double-ageing (PA-DA) are systematically investigated. The hardness and strength of aged 7A46 alloy follows an order of T6>PA-DA > DA and the rank of corrosion resistance is PA-DA > DA > T6. The small size and dispersed distribution of matrix precipitates (MPs) lead to the high hardness and strength of T6 alloy, and low hetero-phase potential differences and less formation probability of corrosion galvanic couples enhance the corrosion resistance of PA-DA alloy. Intergranular corrosion (IGC) test results reveal that considerable potential differences promote the formation rate and the quantity of corrosive-batteries between the matrix and grain boundary precipitations (GBPs) or precipitate-free zones (PFZs). The exfoliation corrosion (EXCO) rate and the weight gain trend of corrosion products are related to the oxide film formation rate and corrosion products accumulation. Localized anodic dissolution and hydrogen embrittlement can induce the stress cracking corrosion (SCC).

Effect of strain path during cold rolling on the microstructure, texture, and mechanical properties of AA2024 aluminum alloy

In this study, the effect of strain path during asymmetric cold rolling process on the microstructure, texture, and mechanical properties of AA2024 aluminum alloy was investigated. Optical microscopy (OM), scanning electron microscopy (SEM), and x-ray diffraction (XRD) were employed to characterize the microstructures and textures. The results showed that the average grain size of cold-rolled samples decreased compared to the as-received AA2024 alloy due to the occurrence of dynamic recrystallization (DRX). The number of DRX grains in the cross-rolled sample was larger than the unidirectional and reverse rolled samples owing to the higher stored strain energy and recrystallization rate of the cross-rolled AA2024. By performing the asymmetric cold rolling in all strain paths, the hardness increased due to increasing the stored strain energy and decreasing the grain size. The hardness and tensile strength of unidirectional and cross-rolled samples was equal. The presence of stronger hard orientations such as [111]∣∣RD in the unidirectional rolled sample compensated its higher grain size and lower stored energy. The overall intensity of components especially hard orientations of cross-rolled sample was much lower than other samples. On the other hand, some new and soft orientations, i.e. [313]∣∣ND and [323]∣∣TD, developed during cross rolling. These resulted in the production of an isotropic AA2024 sheet via asymmetric cross rolling. The fracture mode of deformed samples was a combination of ductile and brittle ruptures owing to increasing the stored strain energy and decreasing the ductility caused by asymmetric cold rolling. However, the contribution of ductile fracture in the cross-rolled sample was higher than the unidirectional and reverse rolled samples.

Application of hot forming cold die quenching for facilitating equal channel angular pressing of AA2024 aluminum alloy

The effect of one pass hot forming cold die quenching (HFQ) in equal channel angular pressing (ECAP) on the evolution of hardness, tensile properties and microstructure of AA2024 aluminum alloy is investigated. Since AA2024 is a heat treatable aluminum alloy, it is sensitive to the cooling process applied before deformation or aging. Therefore, samples are considered in air cooled (AC) and water quenched (WQ) conditions and the results are compared with those obtained in HFQ-ECAP. In addition, hardness and tensile properties are investigated in as-deformed and aged conditions to understand the response of the alloy to aging. It is found that distribution of precipitates, hardness and tensile properties in the aged samples significantly depend on the cooling process prior to deformation. Significant increases in hardness (24 and 22%) and strength are observed when the WQ and HFQ samples are aged after one pass ECAP. However, an effective precipitation hardening is not achieved when AC cooling is applied. In addition, much more effective strengthening and precipitation hardening with respect to AC samples are observed by utilizing HFQ. Maximum hardness (201 Hv), yield strength (YS) (446 MPa) and ultimate tensile strength (UTS) (558 MPa) are achieved in the WQ sample after ECAP and aging treatment. Similar properties are achieved in HFQ-ECAP samples after aging treatment which respectively equal 190 Hv, 446 MPa and 560 MPa for hardness, YS and UTS. Indeed, due to its very similar achieved mechanical properties, the HFQ-ECAP is found as an effective way to replace WQ-ECAP of AA2024 alloy.

PENGARUH KUAT ARUS PADA PENGELASAN PADUAN ALUMINIUM 6061 DENGAN MENGGUNAKAN METODE LAS TIG TERHADAP KEKERASAN DAN STRUKTUR MIKRO

<em>The objective of research was to find out the effect of current on microstructure and hardness value in Aluminium Alloy 6061 before (raw material) and after welding using Tungsten Inert Gas (TIG) welding method with filler rod ER4043. This research uses experiment methods. Technique of analyzing data used was a descriptive comparative research. The instruments used for testing microstructure and hardness were Olympus Metallurgical Microscope and Vikers Hardness Tester. Base on the result of research, it could be concluded that the result of microstructure testing showed the reduced Mg<sub>2</sub>Si phase width after welding. In raw material, the Mg<sub>2</sub>Si phase seemed to diffuse surrounding the α-Al phase surface, but the result of welding using TIG welding method with current of I00 A, 110 A, and 115A showed that Mg<sub>2</sub>Si phase reduced in each specimen, so that α-Al phase was very dominant. The hardness value of hardness result showed the different hardness level. The specimen with current of 110A had higher hardness level of 65.4 VHN than the specimen with current of 100 A (55.7 VHN) and 115 A (55.9 VHN). The result of hardness testing on raw material was 120.4 VHN. This research showed that the welding using varying current changed microstructure and affected the hardness value of Aluminum Alloy 6061.</em>

Influence of extrusion parameters on microstructure, texture, and second-phase particles in an Al-Mg-Si alloy

The extrusion parameters greatly influence the microstructures of aluminum alloys, and further determine the mechanical properties of the final products. In this work, using a self-designed experimental device, a series of extrusion experiments was conducted to investigate the influence of the extrusion parameters on the microstructure, crystallographic texture, and second-phase particles in the Al-Mg-Si aluminum alloy (AA6N01), which is widely applied in the bodies of high-speed trains. Firstly, the billet discard in the press container was taken out for analyzing the material flow and microstructural evolution during the extrusion process. The results showed that continuous dynamic recrystallization occurred, and the initially coarse equiaxed grains in the as-homogenized billet evolved gradually into fine equiaxed grains at the die exit due to their dynamic recovery and dynamic recrystallization. More importantly, coarse grain layers were observed on the surface of the extruded profiles under specific extrusion conditions (460 °C/48 mm/min and 520 °C/48 mm/min). Then, the textures on the surface and at the center of the profiles were analyzed under different extrusion conditions by electron backscatter diffraction. The results showed that the textures of all the extruded profiles were mainly along <100> and <111 > , but the texture intensity was higher at the profile's center than that on the surface under the same extrusion condition. Finally, the second-phase particles in the as-homogenized billet and as-extruded profiles were compared and analyzed. The Fe-rich particles were broken under deformation conditions and their sizes decreased during the extrusion process. However, they were all still distributed on the grain boundaries after deformation, and the composition and content remained unchanged. The Mg2Si particles served as the main strengthening phase in AA6N01, and they were greatly aggregated as the extrusion temperature increased and the extrusion speed decreased.

Effect of Erbium Addition on the Microstructure and Mechanical Properties of Aluminium Alloy

The effect of rare earth metal erbium (Er) modification on the microstructure and mechanical properties of aluminium alloys (A380) were investigated using Optical Microscope (OM), Scanning Electronic Microscope (SEM) attached with Electron Dispersive Scanning (EDS), Vicker’s hardness test and Ultimate Tensile Test (UTS). The results show that the addition of Er reduces the size of the silicon particle and improve mechanical properties of the aluminium alloy. In addition, by adding 0.1 wt. % of Er, the mean area (μm2) and aspect ratio value decreased. The coarse plate like existed in the unmodified alloy transformed into fine particle and short rod. The mechanical properties were investigated by using tensile test and Vicker’s hardness test. The ultimate tensile strength test shows that the tensile and the elongation increased 1.32 % and 9.1 % with 0.1 wt. % Er content of the aluminium alloys, respectively. The hardness improved from the addition of 0.1% Er aluminium A380 alloy.

Study of microstructure and mechanical properties of A713 aluminium alloy having an addition of grain refiners Al-3.5 Ti-1.5C and Al-3Cobalt

Abstract Aluminium die casting manufacturing is a prominent for mass production with economical, which is also a challenging with many casting defects which are influenced by many process parameters. The mechanical and microstructural properties of the die cast parts contributes significantly in determining the final quality of the die cast alloy. In the present research work, tensile and hardness test are carried out to study the influences on the mechanical properties of an A713 alloy without and with Al-3.5 Ti-1.5C and Al-3Cobalt as grain refiners. Mechanical properties such as tensile strength and micro hardness were observed which has shown an increase in the case of A713 alloy where grain refiners such as Al-3.5Ti-1.5C and Al-3Cobalt were added as compared to that of without grain refinement. In addition of 0.1 wt% of Al-3.5Ti-1.5C to A713 alloy there was a transition from coarser grains to finer grain structure with an average grain size of 16.6 µm. The finest grain structure was obtained with an addition of 1.0 wt% Al-3.5Ti-1.5C having an average grain size of 15.0 µm. From the SEM it was established that due to the absence of Al-3.5Ti-1.5C the image shows coarser columnar α-Al dentritic like arrangements with non-modified platelets. The addition of 0.1 wt% Al-3.5Ti-1.5C and 1.0 wt% Al-3.5Ti-1.5C with the A713 alloy the grain structure of the alloy shows transition from coarse to fine equiaxed grains.

Effect of rare earth elements on the microstructure and properties of a die-cast aluminum alloy

Abstract The effects of the rare earth elements Ce, La and Sm on the microstructure and mechanical properties of a die-cast aluminum alloy were studied. First, the optimal percentage content of the main elements in the alloy was determined by a single factor and by orthogonal experiments based on the composition range of ADC12 aluminum alloy. The results showed that the optimal percentage content of the main elements in ADC12 die-cast aluminum alloy were 11 wt.-% Si, 2.5 wt.-% Cu, 0.5 wt.-% Mn and 0.3 wt.-% Mg. The tensile strength was 285 MPa and the fracture strain 2.23 %. Then, three rare earth elements of varied contents were added to the above-mentioned aluminum alloy. The tensile strength and elongation of the alloy were increased through the addition of rare earth elements. The comprehensive mechanical property of the alloy was best when Ce, La and Sm levels were at 0.6, 0.4 and 0.2 wt.-%, respectively, in the single factor test. Sm had the largest influence on the comprehensive mechanical properties of the alloy, followed by Ce and La which had the least influence.

Achieving special mechanical properties with considering dwell time of AA5052 sheets welded by a simple novel friction stir spot welding

In this study, a new method was proposed to remove the keyhole with the title of "protrusion friction stir spot welding", and the effect of the tool dwelling time on microstructure and mechanical properties of aluminum alloy 5052 sheets was investigated. Welding was carried out at different dwelling times of 3–18 s at a tool rotational speed of 800 rpm. Macrostructure and microstructure examinations indicated that this new method has the ability to create a non-defect metallurgical joint with a homogeneous and fine grain structure. The results of the micro hardness test showed the hardness reduction of the SZ from 57.4 HV to 48.15HV with increase in the too dwelling time (3–18 s). The tensile properties of the welding samples were evaluated using a tensile shear test. The results showed a reduction in maximum failure load from 4384.6 N to 3331 N with increase in the tool dwelling time (from 3 to 18 s). With considering dwelling time and sheets thickness, the welds produced by the present work illustrated better load capacity than other techniques.

Effect of Friction Stir Processing on Microstructure and Mechanical Properties of AlSi10Mg Aluminum Alloy Produced by Selective Laser Melting

Friction stir processing (FSP) was successfully applied to AlSi10Mg alloy produced by selective laser melting. The microstructure, microhardness, and room-temperature tensile property of the FSPed AlSi10Mg alloy were investigated. The results showed that FSP eliminated the pores of the AlSi10Mg alloy and achieved the microstructural refinement, homogenization, and densification. The grain size was refined from 13.6 μm to 2.3 μm, and relative density increased from 93.3% to 99.6%. An increase in rotation speed led to the enhancement in the density; however, it slightly affected the grain size in this study. The Si particles were homogenously dispersed in the Al matrix, which resulted in uniform distribution of microhardness. FSP led to the increase in the elongation of the AlSi10Mg alloy by 298%, while ultimate tensile strength decreased by only 8%. The Orowan and dislocation strengthening mechanisms were responsible for the loss of strength. FSP has the advantage of acquiring good ductility while maintaining high strength.

Anisotropy of microstructure and properties of high strength hot-extruded processed aluminum alloy

The microstructure and properties of high strength aluminum alloy under extrusion—hot pressing—solid solution-aging treatment were studied by XRD analysis, hardness and conductivity test, tensile test, intergranular corrosion and exfoliation corrosion test. At the same time, the influence of hot compression technology on the properties of the compressed surface was investigated. The results show that there is anisotropy between the properties of aluminum extrusion-hot pressed material, the hardness and conductivity in the Z direction are higher than those in the X and Y directions, and the tensile strength and plasticity are better than those in the Y direction, among which the strength is increased by about 122 MPa and the elongation by about 6.17%. The corrosion resistance also exists in the anisotropy, in which the Z direction has the best intergranular corrosion resistance and the corrosion depth is 167.46 um, the Y direction has the best exfoliation corrosion resistance and the grade reaches PC grade. The thermal compression process is beneficial to improve the plasticity, electrical conductivity and exfoliation corrosion performance of the compressible surface material, but reduces the hardness, tensile strength and inter-granular corrosion performance.

Characterization of the Role of Squeeze Casting on the Microstructure and Mechanical Properties of the T6 Heat Treated 2017A Aluminum Alloy

In this study, the effects of squeeze casting process and T6 heat treatment on the microstructure and mechanical properties of 2017A aluminum alloy were investigated with scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), differential scanning calorimetry (DSC), and microhardness and tensile tests. The results showed that this alloy contained α matrix, θ-Al2Cu, and other phases. Furthermore, the applied pressure and heat treatment refines the microstructure and improve the ultimate tensile strength (UTS) to 296 MPa and the microhardness to 106 HV with the pressure 90 MPa after ageing at 180°C for 6 h. With ageing temperature increasing to 320°C for 6 h, the strength of the alloy declines slightly to 27 MPa. Then, the yield strength drops quickly when temperature reaches over 320°C. The high strength of the alloy in peak-aged condition is caused by a considerable amount of θ′ precipitates. The growth of θ′ precipitates and the generation of θ phase lead to a rapid drop of the strength when temperature is over 180°C.

Microstructure, Mechanical Properties (Strength and Hardness) and Wear Behavior of Chilled Aluminum Alloy (LM-13) Reinforced with Titanium Carbide (TiC) Metal Matrix Composites

This paper deals with the production of aluminum alloy (LM-13) reinforced with titanium carbide (TiC) chilled composites subject to different chilling rates to study the effect of chilling on microstructure, mechanical and tribological behavior. Metallic and non-metallic chills (25 mm thick) were used in this investigation. The specimens taken from casting blocks were tested for their microstructure, strength, hardness and wear behavior. It was found in the present investigation that chilling rate and addition of TiC reinforcement (3 to 12 wt% in steps of 3 wt%) have improved both mechanical properties (strength and hardness) and wear resistance of the composite developed. Out of the chills used, copper chill was found to be good in improving mechanical properties because of its high Volumetric Heat Capacity (VHC). It is concluded from the above investigation that type of chill and hence chilling rate, reinforcement content have an effect on mechanical properties wear behavior.

The Influence of Microstructure of Al-Si Alloy and Microarc Oxidation Modes on Corrosion Resistance of the Formed Coatings

The influence of the initial microstructure of high-silicon aluminum alloy and modes of process microarc oxidation (MAO) on the corrosion resistance of the formed coating has been studied. MAO-layers were formed on samples of AK12D alloy in the initial coarse-grained state and after a strong plastic deformation by torsion. Investigated thickness, microhardness, porosity and corrosion resistance of the coatings. It is established that the characteristics of MAO layers depend largely on the microstructure of the base material, the chemical composition of the electrolyte and the electrical parameters of the MAO process. It is established that severe plastic torsion deformation of the AК12D alloy samples before MAO leads to an increase in coating thickness in ∼2 times. Microhardness of coatings decreases by 1.5-3.0 times and the corrosion resistance deteriorates by 5.9-11.7 times on samples with fine-grained structure. These indicators depend on the modes of the MAO process.

Review of Friction Stir Processing of Aluminium Alloys

An advancement to the principles of friction stir welding is the friction stir processing, a technique for modifying the surface, which involves the modification of the local microstructure by refining the microstructure and through localized plastic deformation of the specimen material. The tool that is involved in the process consists of a rotating tool which has a shoulder and pin inserted into the single piece of material. The area which needs to be examined with this process is traversed by this tool in a desired direction. When the shoulder of the tool and the workpiece comes into contact with each other, with the tool traversing at a particular travelling speed and an optimal rotational speed, friction is developed between the two surfaces. This in turn increases the heat of the material to a limit where the material undergoes plastic deformation. Hence when such an exposure occurs localized plastic deformation and the thermal property increase leads to a drastic change in the local microstructure. Various properties have been examined when the material undergoes friction stir processing which involves the production of nanograin, the surface hardness increases followed by the the fatigue strength, wear property and tensile strength of the material. This review paper focuses mainly on the change in microstructure and mechanical properties of Aluminium alloys and their composites and the effect of FSP process through the study of the current trend and the development of FSP to various parameters.

Evaluation of Microstructure and Formability of Rheocasting Aluminum Alloy by Inclined Cooling Plate

Evaluation of Microstructure and Formability of Rheocasting Aluminum Alloy by Inclined Cooling Plate

Investigations and optimization of friction stir welding process to improve microstructures of aluminum alloys

This work mainly focus on finding the optimal conditions for improving the efficiency of the dissimilar welded joints that were prepared using the friction stir welding (FSW) process. To carry out ...