Microstructure Of Aluminum Alloy Research Articles

Heterogeneous microstructure and deformation behavior of an automotive grade aluminum alloy

Aluminum alloy is today considered as a prime selection for manufacturing lightweight structural components in the automotive industry to increase fuel efficiency and reduce harmful emissions. The aim of this study was to identify the effect of microstructure and strain rate on the tensile deformation behavior of a high-pressure die-cast Silafont®-36 alloy, with special attention to strain hardening behavior and deformation mechanisms. The alloy consisted of randomly oriented primary α-Al phase and Al–Si eutectic structure in a form of heterogeneous microstructures, with Sr-modified Si particles exhibiting a coral-like fibrous network. The local misorientations in most primary α-Al grains was below 1°, suggesting strain-free grains along with some extent of near-boundary residual strains due to the thermal mismatch between aluminum and silicon. A superior strength-ductility combination was achieved, along with enhanced Young’s modulus and quality index owing to the unique heterogeneous microstructures. The cast alloy exhibited a smooth deformation characteristic with good coordination deformation and strong strain hardening capacity. Strain hardening exponents evaluated via the equations proposed by Ludwik, Hollomon, Swift, and Afrin et al., respectively, showed basically the absence of strain-rate effect from 1 × 10−5 to 1 × 10−2 s−1. During the tensile deformation, crack initiated from the sample surface and propagated through the alternate microconstituents of softer primary α-Al phase and harder eutectic structure.

Aluminum Alloys with the Addition of Reduced Deep-Sea Nodules

An innovative way to utilize deep-sea manganese nodules is described in this paper. The manganese nodules were reduced by aluminothermy and subsequently added into aluminum as a mixture of alloying elements in their natural ratio. The microstructure and properties of aluminum alloys containing 1.2, 7.7, and 9.7 wt % of reduced nodules were studied. The alloys were formed by Al matrix and minor amounts of Al6(Fe,Mn) and Al11Fe7 intermetallic phases. The alloys containing a higher amount of reduced nodules are characterized by very good thermal stability. The obtained alloys were studied by X-ray diffraction, their microstructure was observed by scanning electron microscopy, and their local chemical composition was analyzed by energy dispersive spectrometer. The hardness of the samples was measured on the initial materials and after long-term annealing. Based on the obtained results, the aluminum alloys, with the addition of reduced deep-sea nodules, can serve as precursors for processing, e.g., by rapid solidification or hot working methods.

On Rough Set Theory on Achieving High Quality Cable Material Production by Green Low Carbon Technology

Abstract As the second largest machinery industry, the energy-intensive cable industry not only creates a lot of economic value but also consumes a lot of energy. It is an inevitable requirement to promote the technological development of the industry in the new era to improve the quality and efficiency and realise industrial energy-saving and consumption reduction. In order to obtain good strength and conductivity, the metal rods of cable are usually heat-treated for several hours or even several days after the rods are extruded, this is a major energy consuming process in traditional production. Based on the background, this study adopted the energy-saving equal-channel angular pressing (ECAP) technology to replace the traditional heating treatment process, and converted the simple heat conduction with thermo-mechanical energy transfer, so as to realise the good strength and conductivity matching of the cable aluminum alloy material. In this study, energy-saving ECAP technology is used to replace the traditional heat treatment process, and heat-mechanical energy transfer is used to replace the simple heat conduction, so as to achieve good strength and conductivity matching of cable aluminum alloy material. The results show that the suitable ECAP process routes can improve the microstructure of aluminum alloy with higher strength and conductivity than the traditional heating process. The research results can be used for technology upgrading and low carbon production in cable industry due to the significantly time reduction of the energy-consuming heat treatment and the high-efficient obtainment of high-quality production.

Optimized preparation of deep cryogenic treated steel and Al-alloy samples for optimal microstructure imaging results

The research investigates the varying effect of commonly used etchants for revealing the microstructure of steels and aluminum alloys. Selected representatives of different types of tool steels and aluminum alloys were chosen to indicate the general effects of etching on different phases with different elemental contents and enrichments. The representatives were also investigated under two different preparation states. One state of the materials was selected based on the heat and forming processing determined by the producer of the selected materials. Whereas the other state is developed by a modified heat treatment procedure with included deep cryogenic treatment processing step. The purpose of this study is to provide a systematic overview for the evaluation of microstructure of selected materials with various etching reagents based on their different processing history. The intent of this research is also to deliver clear guidelines to the growing community involved in cryogenic processing of metals for the most in-depth microstructural observation with etching of the metallographically prepared sample surface. It was determined, that the optimal etching reagents are different for the same materials under different processing conditions. For the cryogenically treated tool steels, the optimal reagents for both examples was determined to be nital and Groessbeck’s reagent. Whereas for the aluminum alloy the combination of Weck’s and modified Keller’s reagent was determined as the most optimal etching reagents.

A Comparison between Tungsten Inert Gas Welded Joints Welded by Commercial ER5183 Filler and Al–Mg–Zn–Sc–Zr–Mn Filler on Microstructure and Properties in 7075-T651 Aluminum Alloys

A 7075-T651 aluminum alloy was successfully welded by tungsten inert gas welding using commercial ER5183 wire and Al–5Mg–1Zn–0.3Sc–0.15Zr welding wire containing different contents of Mn. The microstructure, corresponding mechanical properties, and the corrosion behavior of the welded joint were investigated by microscopy methods, tensile tests, and corrosion tests. The results revealed that Al3(Sc,Zr) particles were distributed in a small amount in the welds and refined the primary α-Al grain. The addition of Mn gives a strong interaction of improving fracture strength, micro-hardness, and corrosion resistance reducing the harmful influence of iron, as a result, the properties of the welded joint were enhanced. And the increase of Mn content improves the tensile strength and hardness of welds, which could be attributed to the refinement of eutectic T phase by Mn. Potentiodynamic polarization tests revealed that the corrosion resistance of welds increased with the increase of Mn content. Compared with the welded joint using commercial filler, the welded joint with Al–Mg–Zn–Sc–Zr–Mn filler exhibited a higher resistance to stress corrosion cracking (SCC). In conclusion, Al–Mg–Zn–Sc–Zr–Mn filler can be using for welding 7XXX aluminum alloys.

Evaluation of Mechanical, Microstructures and Wear Behaviours of Aluminium Alloy Reinforced with Mussel Shell Powder for Automobile Applications

This paper aims to investigate the mechanical (tensile, hardness, impact, elongation), microstructure and wear behaviours of aluminium alloy reinforced with mussel shell powder (MSP) at different weight percentages (0 wt. % to 15 wt. %) at 3 wt. % interval. The mussel shell powder was characterized by X-ray fluorescence (XRF). The matrix and the composites’ morphology were studied using a scanning electron microscope attached with energy dispersive spectroscopy for the distribution of mussel shell powder particles within the matrix. The wear behaviour of the alloy and composites produced at various reinforcements were carried out using a Taber abrasion wear-testing machine. The XRF showed the compositions of MSP to contain calcium oxide (95.70 %), silica (0.83 %) and others. Mechanical properties showed that tensile values increase with increases in MSP, hardness value increases from 6 wt. % to 15 wt. % of MSP. The impact energy decreased from 42.6 J at 3 wt. % to 22.6 J at 15 wt. %; the percentage elongation also decreased from 37.4 % at 3 wt. % to 20.5 % at 15 wt. % MSP, respectively. The bending stress results increase with increases in the percentage of reinforcement. The morphologies revealed that uniform distribution of MSP within the matrix resulted to improvement in mechanical properties. The wear resistance of the composites increases with increase in the applied load and decreases with increases in the weight percentage of MSP and can be used in the production of brake pads and insulators in the automobile industry.

Microstructure and properties of aluminium alloy 6082 formed by the Hot Form Quench process

During a process development trial, two identical structural automotive parts were formed from a rolled sheet of commercial 6082 Al alloy by Hot Form Quench (HFQ). The rapid transitional contact between the sheet and the die set during die closing imposed a range of complex cooling histories on different locations in the parts. After in-die quenching, one HFQ part was naturally aged at room temperature, while the other was peak-aged at 185 °C for 7 h. The microstructure was compared at two extreme locations; the flange, where die contact is instantaneous leading to immediate rapid cooling, and the sidewall, where the material cools more slowly in air before rapid quenching. After HFQ, some small quench induced grain boundary precipitates were observed in the sidewall specimen but not in the flange. However, subsequent artificial ageing led to a convergence of the microstructures. Consequently, hardness was found to be constant at both locations, and no loss of hardening potential was observed in either case compared with T6 sheet. Samples of the as-received material were subjected to selected quench-hold-quench-age experiments to mimic the HFQ microstructures. Tensile tests showed that the ductility and failure mechanism is insensitive to the small differences in grain boundary microstructure as observed in the HFQ component.

Effects of Cooling Rate on the Microstructure, Mechanical Properties and Corrosion Resistance of 6xxx Aluminium Alloy

The applicability of materials is highly dependent on its microstructure and mechanical properties. Aluminium alloy is being used extensively under diverse conditions. This study investigates the effects of cooling rate on the microstructure, mechanical properties and corrosion resistance of 6xxx-series aluminium alloy. Aluminium ingot was melted in a muffle furnace and cast into rods. The cooling rate was controlled by holding the moulds at different temperatures. Microstructural characteristics were examined by optical microscopy. Mechanical properties such as impact strength, hardness, and tensile strength were analysed using standard methods. Corrosion resistance was evaluated by potentiodynamic polarization. It was found that microstructures are dominated by ferrite and pearlite phases with different morphologies and grain sizes depending on the cooling rate. Increasing the cooling rate resulted in microstructural refinement and chemical homogeneity, improvement in mechanical properties and corrosion resistance of the 6xxx alloy.

Effects of welding parameters on the microstructure and mechanical properties of the AA6061 aluminium alloy joined by a Yb: YAG laser beam

In this study, the effects of Yb: YAG laser welding parameters on the microstructure and mechanical properties of AA6061-T4 joints were analysed. Samples without any welding defects such as porosity, melt pool collapse, and hot cracking were produced with different welding parameters. Energetic processing parameters had a significant influence on the fusion zone (FZ) and heat-affected zone (HAZ) microstructure and dimensions, in addition to local and global mechanical properties. The weld bead width increased with increasing power and energy densities and reduced the weld bead tensile properties. High welding travel speed produced a more elongated weld pool and ripples resulted in a ‘V’ shape. A significant quantity of axial heterogeneous nucleation was observed in the FZ centre of these weld beads because of the low-energy density. In contrast, low welding travel speed produced C-shaped ripples and a few axial grain nucleation sites in the FZ. The latter was evidence of a slower solidification rate. Dendrite secondary arm spacing measurements confirmed this hypothesis. It was observed that axial grains in the FZ centre improve the weld bead tensile properties. Compared to the base material (BM), the hardness in the FZ was reduced and identical in the HAZ. The FZ hardness depended on the welding parameters. Digital image correlation (DIC) strain measurements indicated higher deformation near the FZ, but when geometrical defects were removed, the FZ deformed more homogeneously.

Microstructure and Mechanical Properties of AA7075 Aluminum Alloy Fabricated by Spark Plasma Sintering (SPS).

AA7075 aluminum alloy is widely used for several high-technology applications for its high mechanical strength to weight ratio but is still the subject of several studies seeking a further increase in its mechanical properties. A commercial powder is used, either as-received or after ball-milling. Dense AA7075 samples are prepared in one step by Spark Plasma Sintering, at 550 °C with a holding time of 15 min and a uniaxial pressure of 100 MPa. No additional heat treatment is performed. Laser granulometry, X-ray diffraction and optical- and scanning electron microscopy show that both grain size and morphology are preserved in the dense samples, due to the relatively low temperature and short sintering time used. The samples prepared using the ball-milled powder exhibit both higher Vickers microhardness and transverse fracture strength values than those prepared using the raw powder, reflecting the finer microstructure.

A Review of Aluminum Alloy Fabricated by Different Processes of Wire Arc Additive Manufacturing

Due to the advantages of high deposition rate, low equipment cost and high material utilization rate, aluminum alloy fabricated by wire arc additive manufacturing (WAAM) has been widely concerned by scholars and scientific institutions. This article reviews the features of aluminum alloy fabricated by different WAAM processes (GMAW-based, GTAW-based, CMT-based, PAW-based). Research status of the porosity, dimensional accuracy, microstructure and mechanical properties of aluminum alloy in different process is analyzed. General tendency of microstructure and mechanical properties were discussed, and suggestions for the future research direction were put forward including mandatory constraint on molten pool and structural topological optimization.

Interesting phenomena for Al-Zn-Mg aluminum alloy after two years of storage: A comparative study on microstructure, mechanical properties and corrosion behavior of aluminum alloy with different aging treatments

This work presents a comparison of microstructure, mechanical properties and corrosion behavior of naturally aged (NA) and artificially aged (AA) alloys after two years of storage. The results showed that numerous finer precipitates distributed in NA alloys, resulting in better mechanical response but higher corrosion sensitivity, while the microstructure of AA alloys were almost the same as two years before, the tensile results showed the initial necking phenomenon but limited elongation caused by presence of coarse precipitates and high-density dislocations, whilst its corrosion resistance was better than NA alloys, reflecting from smaller pits and more protective components of corrosion products.

Effect of SiO2 flux on the depth of penetration, microstructure, texture and mechanical behavior of AA6063 T6 aluminum alloy using activated TIG welding

Effect of SiO2 flux on the depth of penetration, microstructure, texture and mechanical behavior of AA6063 T6 aluminum alloy using activated TIG welding

Enhancement of mechanical properties and tribological properties of aluminum using Iron(Fe) and Nickel(Ni) additives

Inmodern times it is seen that the use of aluminum alloys has increased greatly in automobile, aerospace, marine, and various other fields. This is due to the fact that aluminum alloys have superior advantages when it comes to corrosion resistance, strength to weight ratio characteristics, and high machinability when it is compared with steel. In this paper a study on the mechanical, tribological properties and microstructure of aluminum alloy with variations in Nickel (Ni) and Iron (Fe). Previous studies that have been conducted in this field have dealt with aluminum additives of different compositions with the study of only mechanical properties or microstructure. Our project deals with the study in the changes of properties and microstructure analysis of Iron(Fe) and Nickel(Ni), aluminum-based alloy added to which the tribological studies and the correlation is studied with the variations in the metal concentration, Thus the study and development of these alloys are important as it paves the way for the new generation of mechanical components with superior properties. Also, our paper deals with the fabrication of a brake disc rotor with the most suitable alloy among the three. The tensile strength, hardness, and surface characteristics of all the profiles were studied in detail and presented. The 7% of Iron powder in the profile has the highest tensile strength.

Numerical simulations of solidification microstructure evolution process for commercial-purity aluminum alloys inoculated by Al-Ti-B refiner

Solidification microstructure of aluminum alloy has a great influence on the properties of the casting. An aluminum alloy with the structure of fine equiaxed grains has low casting defects and presents excellent mechanical properties. Recently, chemical inoculation by adding grain refiner is the technique most extensively used to achieve a fine, equiaxed grain structure of Al alloy in the industrial production. In order to investigate the detailed solidification microstructure evolution of the alloy, many numerical models have been proposed. Cellular automaton method is one of the powerful tools for simulating the morphology evolution of detailed grains in the solidification process of alloy. However, the present cellular automata model has a shortcoming, that is, its calculation of the nucleation rate is based on the experimental number density of grains. In this work, a population dynamics-cellular automaton model is developed for describing the solidification microstructure evolution of the inoculated aluminum alloy. The model takes account of the heterogeneous nucleation of α-Al nucleus, the initial spherical growth of <i>α</i>-Al grains and the dendritic growth process. The model is used for simulating the solidification microstructure evolution of the commercial-purity aluminum (CP-Al) inoculated by Al-5Ti-1B master alloy. The results indicate that the heterogeneous nucleation process of α-Al can be divided into the two stages. In the early stage of nucleation, there are enough effective particles in the melt. The nucleation rate of <i>α</i>-Al increases with the increase of the undercooling of the melt. After a short time, the nucleation of α-Al is dominated by the number density of the effective particles in the melt. Nucleation process stops when the recalescence takes place. The effects of the additive amount of Al-5Ti-1B master alloy and the cooling rate of the melt on the solidification microstructure of the CP-Al are investigated by using the established model. The final solidification structures of CP-Al are predicted. And a comparison between the predicted results and the experimental ones shows that they are in good agreement with each other.

Effect of process parameters on the microstructure of aluminum alloys obtained by semi continuous casting

Effect of process parameters on the microstructure of aluminum alloys obtained by semi continuous casting

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.

Morphological characteristics of Al3Sc particles and crystallographic orientation relationships of Al3Sc/Al interface in cast Al-Sc alloy

As a new type of grain refiner, rare earth element Sc has a strong grain refining effect on the microstructure of cast aluminum alloys. During the solidification of Sc-containing aluminum alloys, Al3Sc particles are formed in the molten metal and act as heterogeneous nucleation cores of Al in the nucleation process, which significantly increases the nucleation rate and refines the grains. In this paper, a focused ion beam (FIB) microscope was used to extract Al3Sc particles from an Al-Sc alloy, and the internal structure of the particles was systematically observed. At the same time, a scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) were used to study the morphological characteristics of particles and the crystallographic orientation relationships (ORs) at the interface. The study found that under the influence of strong anisotropy, the growth rate of Al3Sc crystal high-index crystal plane and low-index crystal plane is significantly different. In the process of crystal growth, the high-index crystal planes grow faster and disappear quickly, and the shape of the crystal can be ultimately determined by the slower-growing low-index crystal planes. Inside the Al3Sc particles, the (111) and (110) planes form coarse dendritic structures, the (100) planes form a large number of fine cell structures, and there are white oxide residues in the center of some particles. At the interface between Al3Sc and Al matrix, two parallel crystallographic ORs were observed, and the atomic arrangement on both sides of the interface was found to be consistent. At the same time, a special pseudomorphic solid (PS) layer was observed at the interface. On the (111) crystal plane, the atomic arrangement of the PS layer was consistent with Al3Sc at an angle of 60° with Al.

Effect of Laser Power on Microstructure and Micro-Galvanic Corrosion Behavior of a 6061-T6 Aluminum Alloy Welding Joints

The 6061-T6 aluminum alloy welding joints were fabricated using gas metal arc welding (GMAW) of various laser powers, and the effect of laser power on the microstructure evolution of the welding joints was investigated. The corrosion behaviors of 6061-T6 aluminum alloy welding joints were investigated in 3.5 wt% NaCl solution using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that the micro-galvanic corrosion initiation from Mg2Si or around the intermetallic particles (Al-Fe-Si) is observed after the immersion test due to the inhomogeneous nature of the microstructure. The preferential dissolution of the Mg2Si and Al-Fe-Si is believed to be the possible cause of pitting corrosion. When the laser power reached 5 kW, the microstructure of the welded joint mainly consisted of Al-Fe-Si rather than the Mg2Si at 2 kW. The relatively higher content of Al-Fe-Si with increasing in laser power would increase the volume of corrosion pits.

Influence of reversible and non-reversible fatigue on the microstructure and mechanical property evolution of 7075-T6 aluminum alloy

Evolution of microstructural features and defects caused by high cycle fatigue loading have the potential to affect post-fatigue global behavior in different ways depending on the material, fatigue loading parameters, and subsequent loading strain rate. This work focuses on the influence of reversible and non-reversible, macroscopic elastic fatigue on the microstructure and subsequent mechanical properties of 7075-T6 aluminum alloy. Subsurface material obtained from interrupted fatigue experiments is used for both microstructural characterization and post-fatigue mechanical property evolution. Crystal plasticity modeling, in conjunction with machine learning, is used to help determine mechanisms contributing to the mechanical property evolution.It was found that the subsequent mechanical behavior was dependent on both the fatigue stress ratio and subsequent loading strain rate. There was a 7% decrease in quasi-static strength after being fatigued with a stress ratio of zero. However, quasi-static strength remained unchanged after being fatigued at other stress ratios. In addition, dynamic tension experiments did not reveal any decreases in strength due to prior fatigue loading. Fatigue-induced voids potentially developed in grains where slip transmission across the grain boundary was less likely to occur. Iron-rich inclusion cracking took place throughout the bulk fatigued material and was mainly limited to larger sized inclusion particles, but there was no evidence it contributed to significant mechanical property changes. Results from this work show how different stress ratios and degrees of dislocation reversibility during high cycle fatigue loading influence the microstructure and post-fatigue global behavior of 7075-T6 aluminum alloy.