Microstructure Of Aluminum Alloy Research Articles

Effect of Heat Treatment on Microstructure and Mechanical Properties of A380 Aluminum Alloy Deposited by Cold Spray

The microstructure and mechanical properties of cold-sprayed bulk A380 alloy were investigated after heat treatment at various conditions, using optical and electron microscopy and tensile and hardness tests, respectively. The results revealed that heat treatment increased the strength and ductility of the cold-sprayed A380 alloy deposits compared with as-sprayed state. Heat treatment showed two different effects on the mechanical properties of the deposits. On the one hand, it resulted in effective diffusion at interparticle boundaries that altered the particle bonding mechanism from pure mechanical interlocking to metallurgical bonding. Thus, the strength and ductility of the material were greatly enhanced. On the other hand, interparticle diffusion during high-temperature heat treatment resulted in growth of the Si phase and pores, which ultimately reduced the strength and elongation of the alloy. This observation was consistent with the hardness results, which showed a decreasing trend with increase of the heat treatment temperature.

Microstructure and mechanical properties of an AA6060 aluminum alloy after cold and warm extrusion

Severe plastic deformation techniques can produce ultrafine-grained aluminum alloys with high strength and ductility, but further processing often requires costly and/or time-consuming machining. In this study, we investigate the potential of an alternative processing route that operates below recrystallization temperature and that can produce fine-grained materials. Cast billets of the age hardening aluminum alloy AA6060 were solution annealed and then extruded at room temperature or at 170°C (which corresponds to the aging temperature of the alloy, and allows for simultaneous forming and aging). The materials were then subjected to an aging treatment. Electron microscopy and mechanical testing were performed to characterize the resulting microstructural features and mechanical properties. Both extruded profiles exhibit similar, strongly graded microstructures with submicron-sized grains in the highly deformed surface layers, and a mixture of coarse and fine grains in the center regions. Despite different processing routes (i.e., cold vs. warm extrusion), both materials are characterized by similar mechanical properties in terms of maximum hardness, strength and ductility; these results are discussed in the light of the relevant microstructural deformation and precipitation mechanisms.

Evaluation of Microstructure, Mechanical Properties and Corrosion Resistance of Friction Stir-Welded Aluminum and Magnesium Dissimilar Alloys

Microstructure, mechanical properties and corrosion resistance of dissimilar friction stir-welded aluminum and magnesium alloys were investigated by applying three different rotational speeds at two different travel speeds. Sound joints were obtained in all the conditions. The microstructure was examined by an optical and scanning electron microscope, whereas localized chemical information was studied by energy-dispersive spectroscopy. Stir zone microstructure showed mixed bands of Al and Mg with coarse and fine equiaxed grains. Grain size of stir zone reduced compared to base metals, indicated by dynamic recrystallization. More Al patches were observed in the stir zone as rotational speed increased. X-ray diffraction showed the presence of intermetallics in the stir zone. Higher tensile strength and hardness were obtained at a high rotational speed corresponding to low travel speed. Tensile fractured surface indicated brittle nature of joints. Dissimilar friction stir weld joints showed different behaviors in different corrosive environments, and better corrosion resistance was observed at a high rotational speed corresponding to low travel speed (FW3) in a sulfuric and chloride environments. Increasing travel speed did not significantly affect on microstructure, mechanical properties and corrosion resistance as much as the rotational speed.

Three-dimensional characteristics of Fe-rich intermetallics in gravity-cast Al-6Si alloys

Fe-rich intermetallics, especially β-Fe phase, usually forming in the microstructure of cast aluminum alloys, are very detrimental to mechanical properties. In the present work, the effects of Fe content on phase transformation and microstructures were analyzed using a 3D X-ray microscope. Based on the high-resolution 3D X-ray computed tomography, the 3D characteristics of Fe-rich intermetallics and micropores in the gravity-cast Al-6Si alloys with different Fe contents were investigated. In addition, the effect of intermetallics on the microporosity was discussed. The results show that with increasing the Fe content from 0.10wt.% to 0.60wt.%, the volume fraction of Fe-rich intermetallics and the volume of the largest size Fe-rich intermetallic increased, and the 3D morphology of intermetallics changed from fine flake to network aggregation. As the Fe contents increased, the shrinkage pores were characterized, which were rather complex due to the micropores promoted by the intermetallics interactions.

Microstructure and mechanical properties of low-pressure spray-formed Zn-rich aluminum alloy

Microstructure and mechanical properties of low-pressure spray-formed Zn-rich aluminum alloy

The effects of heat treatment on the microstructure and cyclic behavior of A7N01-T4 aluminum alloy

Multi-level tension-compression tests were carried out on A7N01-T4 samples undergoing a series of non-isothermal heat treatments beforehand. Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were performed to analyze the evolution of precipitations. Thermal cycles have significant influence on its plastic constitutive relation. In an interval of peak temperature from 350°C to 450°C, the alloy re-precipitates a large number of non-shearable η′ and η precipitates and mainly presents kinematic hardening characteristic due to the anisotropy induced by Orowan Loop Helped Reverse Bypass (OHRB) mechanism. Strengthening precipitates grow coarser below this interval and decompose into aluminum matrix over this interval, which are in favor of the dislocation shearing and interaction, and lead to an isotropic hardening behavior of the alloy.

Assessment of refining effectiveness of self-prepared nano-(TiNb)C/(NbTi)/Al complex powder inoculation on A356 alloy

Inoculation plays an effective role to refine the microstructure of as-cast aluminium alloys, which strongly depend on the effectiveness of the inoculants. In this work, a new concept of nano-(TiNb)C/(NbTi)/Al complex powder as an inoculant for refining the as-cast aluminium alloys was proposed, and the nano-(TiNb)C/(NbTi)/Al complex powder was prepared by mechanical alloying (MA) method, furthermore, the refining effectiveness of inoculation on A356 alloy was investigated. Results show that the nano-(TiNb)C/(NbTi)/Al complex powder consists of three phases of α-Al, nano-(TiNb)C and (NbTi) solid solution. The nano-(TiNb)C/(NbTi)/Al complex powder as an inoculant have higher refining effectiveness as well as good recyclability on the microstructure of cast A356 alloy, and improve the mechanical properties, especially the ductility.

Effect of Water Cooling on the Microstructure and Mechanical Properties of 6N01 Aluminum Alloy P-MIG-Welded Joints

In-process water cooling was applied to 8-mm-thick 6N01 aluminum alloy joined using the pulsed metal-inert gas (P-MIG) multi-pass welding method. The influence of the cooling conditions on the microstructure and mechanical properties of the welded joints were mainly discussed. Compared with natural cooling, under water cooling, the peak temperature decreased and the cooling rate increased substantially, leading to a decrease in the partially melted zone of the welded joint. The columnar grain sizes adjacent to the fusion boundary were much more elongated under water cooling than under natural cooling. In addition, when water cooling was performed, the width of the softened zone was approximately 6 mm smaller than that with natural cooling, and the overall microhardness of the welded joint was improved. The tensile and nominal yield strengths of the welded joint were approximately 11 and 7 MPa higher under water cooling than under natural cooling, respectively. The fracture surface morphology of the welded joints exhibited typical ductile fracture. Thus, water cooling can optimize the microstructure and improve the mechanical properties of the 6N01 alloy P-MIG-welded joint.

Effect of the Pressure on Microstructure of A380 Aluminum Alloy Prepared by Squeeze Casting

Effects of the solidification pressure on microstructure and mechanical properties of A380 alloy have been experimentally investigated. The obtained results show that the microstructures of the A380 aluminum alloy is fined, the porosity is decreased and the mechanical properties is improved remarkably with the increase of the solidification pressure. When the squeeze pressure increases from 0 MPa to 75MPa, the size of dendrite arm space decreases from 914 μm to 313 μm, reduced by 66%; the eutectic tissue volume fraction increases from 22.5% to 41.36%; the porosity decreases from 4.91% to 1.23%; the secondary dendrite spacing decreases from 39 μm to 18 μm; the size of needle-like β-Al5FeSi phase decreases significantly, and a few Chinese script α-Fe phases was observed in the grain boundary.

Influence of orbital shaking on microstructure and mechanical properties of A380 aluminium alloy produced by lost foam casting

Using vibration for refining microstructure and improve mechanical properties of aluminium alloys castings are in the interest of researchers for many years. Within the framework of these studies mechanical, ultrasonic and electromagnetic vibration applications were carried out. Results of these processes can be summarized as grain refining and changing the dendritic structure into globular. Accordingly increasing in density and mechanical properties were reported. In this work, orbital shaking technique was used alternatively to conventional mechanical vibration in lost foam casting (LFC) of A380 aluminium alloy. In the experiment castings, effects of shaking movement and speed during pouring were investigated. First of all orbital shaking movement has not damage LFC parts and any shape disorder was not occurred. Optical microstructure observations show that, the increase in shaking speed, decrease secondary dendrite arm spacing (SDAS) and partial dendrite arm fractures were determined at 150 rpm shaking. Density and hardness of as cast specimens were increased with shaking and rising shaking speed as well.

The Effect of Lanthanum Addition on the Microstructure and Mechanical Properties of A390 Aluminium Alloy

Aluminium alloys are widely used in the industries and for biomedical applications, because when compared with other materials they provide a high strength-to-weight ratio, better wear resistance, less density, and low coefficient of thermal expansion. However, these alloys possess some limitations in terms of the interactive effects of additives. Therefore, the target of this research is to study the influence of Lanthanum addition of 0.5, 1.0, and 1.5 wt% on the microstructure and mechanical properties of hypereutectic Al–Si alloy. Optical microscopic test, FESEM spectroscopy, XRD, and mechanical properties testing, such as tensile, impact, and hardness test were carried out for characterization purposes. The result indicates the formation of intermetallic compounds, while the value of the secondary dendrite arm spacing became smaller with increasing La addition. The optimum modification of A390 alloy eutectic structure was at 1.0 wt% of La, which improved the ductility from 0.7 to 1.8% and a recorded increase in tensile strength from 100 to 150 MPa.

Effect of ECAP process on structure and hardness of AlMg3 aluminium alloy

Purpose: In the present study, the effect of ECAP die and number of ECAP pressings on the structure evolution and hardness of AlMg3 aluminium alloy was investigated. Design/methodology/approach: Commercial AlMg3 aluminium alloy in the as-cast condition was processed by Equal Channel Angular Pressing method through route A using two different ECAP dies – conventional and modified with additional twist angle. Samples were processed at ambient temperature up to four passes. The investigation was carried out at ambient temperature. Two different ECAP dies were used to investigate the effect of design modification on the possibility of grain refinement to sub-micrometer size. Findings: The experimental results showed that the modification of ECAP die provides to additional grain refinement and introduces a greater amount of plastic strain into the material which results in greater increase in the properties of the investigated material. Research limitations/implications: The presented investigation results were carried out on samples, not on final products. Practical implications: Current research is moving towards to develop high strength materials with increased mechanical properties and refined microstructure that are known as ultra-fine-grained materials, compared to well-known with coarse-grained microstructure. Originality/value: The paper focuses on the investigation of microstructure evolution using mainly polarised light microscopy that reveals shear, micro-shear and slip bands that refine the microstructure of aluminium alloys. In addition, to evaluate the grain size of as ECAPed specimen, EBSD investigation was carried out.

Effect of scandium on microstructure and mechanical properties of high zinc concentration aluminum alloys

This study investigated the effect of Sc addition on the microstructure and mechanical properties of a high-Zn-concentration Al (Al–49Zn) alloy. The addition of 0.5Sc obviously refined the Al grains and Zn phases in the Al–49Zn alloy during solidification. It also suppressed the Al grain coarsening and Zn dissolution in the Al–49Zn alloy during heat treatment because of the pinning effect of nanoscale Al3Sc precipitates and Sc atoms. Given its refined structure and high thermal stability, the Al–49Zn–0.5Sc alloy showed high hardness and mechanical stability after heating.

Evolution of microstructure and mechanical properties of A356 aluminium alloy processed by hot spinning process

The evolution of microstructure and mechanical properties of A356 aluminum alloy subjected to hot spinning process has been investigated. The results indicated that the deformation process homogenized microstructure and improved mechanical properties of the A356 aluminum alloy. During the hot spinning process, eutectic Si particles and Fe-rich phases were fragmented, and porosities were eliminated. In addition, recrystallization of Al matrix and precipitation of AlSiTi phases occurred. The mechanical property testing results indicated that there was a significant increase of ductility and a decrease of average microhardness in deformed alloy over die-cast alloy. This is attributed to uniform distribution of finer spherical eutectic Si particles, the elimination of casting defects and to the recrystallized finer grain structure.

Effect of friction stir welding on microstructure and corrosion behavior of LF6 aluminum alloy

The LF6 aluminum alloy plates were joined by friction stir welding method. The tool rotational (1180 rpm) and transverse speed (0.56 mm s−1) were kept constant during welding of 4 mm thick plates. The microstructural features, hardness and tensile properties of the welded samples were determined to evaluate the structural integrity in comparison with the base metal. The electrochemical behavior of base metal (BM), thermo-mechanically affected zone (TMAZ) and weld nugget zone (WNZ) was also investigated by potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5% NaCl solution. The microstructural study revealed significant grain refinement and agglomeration of β (Mg2Al3) intermetallic precipitates in the WNZ. The relatively higher hardness and a decrease in the ductility (3%) also assured the formation of precipitates β precipitates in the WNZ welded samples. The fracture surface of welded sample also revealed the existence of β precipitates within the elongated dimples which may be considered as the crack initiation sites. The relatively lower corrosion rate (23.68 mpy) and higher charge transfer resistance (403 Ω cm2) of BM compared to WNZ could be associated with the galvanic dissolution of Al-matrix through competitive charge transfer and relaxation (adsorption/desorption of intermediate species) processes specifically at the vicinity of the β precipitates.

Micro-segregations in semi-solid microstructure of both Ti-contained and Ti-less A356 aluminum alloys characterized by a color etching method

Micro-segregations in semi-solid microstructure of both Ti-contained and Ti-less A356 aluminum alloys characterized by a color etching method

Mechanical and Microstructural Properties of 2618 Al-Alloy Processed by SLM Remelting Strategy

Paper deals with the comparison of mechanical properties and microstructure of aluminium alloy 2618 fabricated by Selective Laser Melting (SLM) and material of the same grade manufactured by standard extrusion process. The SLM specimens were fabricated with different processing strategies (meander and remelting). Presence of cracks was found in both cases of used strategies, but in case of meander strategy, crack are of shorter character and distributed rather within individual welds. In case of remelting strategy, cracks are oriented mostly parallel to building direction and transcend fusion boundaries (FB) across several layers. It was found that defects present in microstructure of SLM material significantly affect its mechanical properties. Ultimate tensile strength (UTS) for extruded material reached 392 MPa, while for SLM material produced with meander strategy UTS was 273 MPa and for remelting strategy it was 24 MPa only.

The effect of pressure and pouring temperature on the porosity, microstructure, hardness and yield stress of AA2024 aluminum alloy during the squeeze casting process

The effect of pressure and pouring temperature on the microstructure, porosity, hardness and yield stress of AA2024 aluminum alloy during squeeze casting process was investigated. At a constant pouring temperature (700°C), by increasing the applied pressure up to 140MPa, the hardness increased from 125 HBN to 152 HBN while the yield stress increased from 235MPa to 340. Moreover, by increasing the applied pressure (to 140MPa) and reducing the pouring temperature (at 700°C), the DAS size and the porosity diameter decreased to 12.5 and 0.25μm, respectively. Thus, the density increased to 2.75 (g/cm3). At a pressure of 140MPa and 700°C, an ultra-fine grain structure with an average grain size of 80nm was observed. At squeezing pressures greater than 70MPa, the effect of pouring temperature was less important.

The Effect of Deformation Ratio and Heat Treatment Time on the Microstructure and Mechanical Properties of A356 Aluminium Alloy During SIMA Process

The influence of Strain Induced Melt Activated (SIMA) parameters on the globularization of α-Al and microstructure in A356 aluminium alloy were investigated in the present study. After production of samples using conventional permanent mold casting and cold rolling at various reduction, they were heat treated at 590°C for different holding time to spherodize the microstructure. The results indicated that, the grains became smaller, more spherical and having a homogenous distribution by increasing the deformation ratio. Increasing the holding time in heat treatment results the growth of globular grains. The necessary strain for recrystallization is about 15% and the optimum condition was achieved in the samples were 15% rolled and heat treated for 15 minutes at semi-solid temperature, regarding the maximum shape factor and minimum globular grains size. Further increasing in holding time is responsible for grain growth and hardness decline.

RESEARCH ON THE EFFECT OF AD1M ALLOY ANISOTROPY ON THE GEOMETRY OF HOLLOW CYLINDRICAL PARTS IN DRAWING

The paper covers the effect of material anisotropy on the nature of deformation and geometrical dimensions of the finished capsule made of AD1M aluminum alloy in the drawing process. Metallographic, X-ray diffraction, full-scale production, and computer studies were conducted and the mechanical properties of the material were determined in order to identify the factors of the material anisotropy. Finite element analysis of the drawing process was conducted, where isotropic and macroanisotropic models, together with a model which factored in the microstructure of AD1M aluminum alloy, were considered as the treated material. It was found that only the macroanisotropic model and, to a greater extent, the finite element model which factored in the material microstructure in contrast to the isotropic model, allowed studying the earing process. It was shown that factoring in the sheet material anisotropy in the manufacture of hollow cylindrical parts by die stamping made it possible to determine the nature of metal flow more accurately and realistically and thus determine the final geometry of produced parts and consequently to create a stable process and improve product performance.