7xxx Series Research Articles

Characterization of Zr-Containing Dispersoids in Al-Zn-Mg-Cu Alloys by Small-Angle Scattering.

The characterization of Zr-containing dispersoids in aluminum alloys is challenging due to their broad size distribution, low volume fraction, and heterogeneous distribution within the grains. In this work, small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) were compared to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) regarding their capability to characterize Zr-containing dispersoids in aluminum alloys. It was demonstrated that both scattering techniques are suitable tools to characterize dispersoids in a multi-phase industrial 7xxx series aluminum alloy. While SAXS is more sensitive than SANS due to the high electron density of Zr-containing dispersoids, SANS has the advantage of being able to probe a much larger sample volume. The combination of both scattering techniques allows for the verification that the contribution from dispersoids can be separated from that of other precipitate phases such as the S-phase or GP-zones. The size distributions obtained from SAXS, SANS and TEM showed good agreement. The SEM-derived size distributions were, however, found to significantly deviate from those of the other techniques, which can be explained by considering the resolution-limited restrictions of the different techniques.

Achieving superior dispersion-strengthening effect in an AA5xxx Al-Mg-Mn alloy by mico-alloying

5xxx Al-Mg based alloys are widely applied as non-heat-treatable alloys. In this work, we designed a dispersion-strengthening Al-4Mg-1Mn-0.3Fe-0.2Si-0.2Zr-0.2Cr (wt.%) alloy. By applying ramp heating and 400 °C isothermal aging, a significant dispersion-strengthening effect through the formation of various types of dispersoids was achieved. Detailed scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis revealed the precipitation behaviors of nanoscale Mn-rich dispersoids and Al3Zr nanoparticles during heat treatments. As a result, an increment of 48 MPa in yield strength was obtained compared with the reference 5182 alloy. Meanwhile, the modified alloy shows a good heat resistance at 400 °C with little loss of yield strength until 200 h of heating. This has been attributed to the further precipitation of Al3Zr particles which counteracts the coarsening of Mn-rich dispersoids. Moreover, the addition of peritectic element Cr was found to significantly promote the precipitation of Al6(Mn,Fe,Cr) in dendritic center regions, thus improving their global distribution across dendrite arms. The presence of dense dispersoids can also improve the recrystallization resistance of the deformed alloy during annealing, thus retaining the deformation fiber structure and significantly retarding the recrystallization behavior. This research demonstrates an effective strategy to develop high-performance 5xxx series alloys strengthened via dispersoids.

Increasing the build rate of high-strength aluminium alloys produced by laser powder bed fusion

Aluminium alloys from the 2xxx series represent important structural materials due to their optimal combination of strength and corrosion resistance. However, their production by means of laser powder bed fusion (PBF-LB/M) is hampered by the presence of detrimental pores and hot cracks. These defects can be mitigated with appropriate process parameters investigations, often at the expense of the build rate.In this study, a combination of modelling and experimental work is adopted to predict the consolidation behaviour of AA2024, a well-known high-strength Al alloy, in regimes characterised by a progressive increase of build rate. The melt pool geometries are predicted as a function of various process parameters using the Rosenthal solution and variable values of absorptivity. This leads to a facile production of near-full dense crack-free parts at an increasing build rate. The analysis of the specimens produced with such processing parameters reveals that the microstructural features and mechanical properties of AA2024 are largely preserved when build rate is increased.Our approach can be easily implemented in standard PBF-LB/M systems as it does not rely on machine adaptations. Therefore, our new proposed approach might result in a practical solution to increase the productivity of other high-strength Al-alloys in industrial settings.

AUSTRAL WRIGHT 5083

Abstract Austral Wright 5083 is a wrought, non-heat-treatable, aluminum-magnesium-manganese-chromium alloy (5xxx series). It has the highest strength of the non-heat-treatable alloys but is not recommended for use at temperatures in excess of 65 °C (150 °F). It is among the most widely used aluminum alloys for marine applications. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: Al-493. Producer or source: Austral Wright Metals.

Dependency of mechanical properties on artificial aging conditions for EN AW 6082 aluminum alloy

Aluminum 6xxx series alloys attract attention owing to their decent strength, formability and corrosion characteristics. Mechanical properties of these alloys can be altered via precipitation hardening by applying an aging treatment known as artificial aging (AA). This investigation was focused on the behavior of mechanical properties of EN AW 6082 alloy for various aging conditions. Mechanical property response for different heat treatment procedures were analyzed together with DSC results and TEM micrographs. Solution heat treatment (SHT) temperature was found to affect the obtained yield strengths after AA considerably and higher SHT temperatures lead to higher yield strength for same artificial aging condition. It was also shown that yield strength values obtained after 480 min—180 °C artificial aging can be surpassed in shorter times at higher artificial aging temperatures. Aging times as short as 60 min may be employed using temperatures above 200 °C to obtain higher strength than 480 min—180 °C aging. Linear relationships between Vickers hardness and mechanical strengths were suggested for the complete data of the study. Negative effects of over-aging on ductility were presented and β′′ precipitates which are responsible for hardening during aging were presented using TEM micrographs. Additionally, high cycle fatigue tests were conducted for AA procedures 480 min—180 °C and 240 min—200 °C and similar fatigue strengths were reported.

The electrochemical degradation, wear behavior and machining of metal matrix composites based on 6xxx aluminum alloy with ceramic particulate reinforcements; a brief review

6xxx series aluminum alloy-based metal matrix composite materials are finding greater applicability in various fields like marine, aerospace and automobile industries. In fact, the diverse nature of the availability of ceramic particles and the hybrid combinations of the reinforcements make them versatile in superior properties as well as applications. More over these composites are latest additions to the novel materials developed in recent decades and hence the end products of these composites are reaching the markets in recent times after several years of optimization studies. There is a need to compose the material properties as a review document so that the research on the same domain will get accelerated. Hence it is appropriate to make a comprehensive study about 6xxx aluminum alloy-based metal matric composites in terms of its corrosion behavior in aggressive environments, wear behavior in engineering applications and feasibility of manufacturing the end products using the composite.

Machine-learning assisted compositional optimization of 2xxx series aluminum alloys towards tensile strength

High-strength 2xxx series aluminum alloys (Al-Cu system) have been favored by the aerospace and railway transportation industries. Traditionally, developing new materials with targeted properties is guided by extensive experiments and expert experience, causing the development process to be dismayingly slow and expensive. Here, a Kriging model-based efficient global optimization(EGO) lgorithm is applied to search for new 2xxx series aluminum alloys with high tensile strength in a huge search space. After four iterations, the alloy’s ultimate tensile strength increased by 60 MPa, which is higher than that of the best alloy in the initial data set. This study demonstrates the feasibility of using machine-learning to search for 2xxx alloys with good mechanical performance.

Characterization of Hot Extruded Hybrid Composites Al 2024 Metal Matrix Reinforced with TiO2 and ZrO2

In this study, the microstructure and mechanical properties of Al 2024 powder, the prominent type of Al 2XXX series aluminum alloys widely used in the aerospace industry, and TiO2 and ZrO2 reinforcement elements used to improve material properties were investigated. Each reinforcement element is included in the material at the rate of 10%. For hybrid composite sample production, 10% hybrid composite material was procured by adding each reinforcing element equally. For each sample, powders were mixed in a 3D mixer to ensure an equal distribution of matrix powder and reinforcement elements in the samples. The samples were churned out by subjecting the two-stage them to a one-way hot press process. The furnace temperature was kept at 600 o C to preserve samples. Density and microstructure analyses were performed on the formed samples, and the results were evaluated. After all, the Archimedean density measurement method was used to obtain final densities, these samples were taken to bakelite for optical images, then scanning electron microscope (SEM) and Brinell hardness of the samples was measured. The cross-fracture strength test was completed to analyze each sample’s microstructural behavior. Finally, the theoretical radiation shielding properties of each sample were investigated. The Phy-X/PSD program was used to examine the radiation permeability properties. According to the test and analysis results, the effect of reinforcement elements on the material was determined. As a result, the highest hardness value measured was 97.5 HB at the 10% ZrO2 -reinforced MMCs. However, the relative density of the hybrid composite is better than ZrO2-reinforced MMCs. Thus, the best cross-fracture strength measured was 635 MPa in 10% hybrid MMCs. The radiation shielding parameters showed that the 10% ZrO2 -reinforced MMCs are best for shielding. Therefore, the second reasonable material for radiation shielding is hybrid reinforced materials. In the final decision, hybrid composite materials became prominent because the distinctive features of each material enhanced the samples.

The role of filler material selection in the laser welding process of deformable 6xxx series aluminum alloys

The automotive industry is facing stringent requirements regarding the reduction of fuel consumption and the reduction of greenhouse gas emissions. The use of aluminum alloys and laser welding technology allows the fulfillment of these targets by creating the opportunity to decrease the weight of the vehicles. One of the variables related to the laser welding process is the filler material. In the case of heat-hardenable alloys, the role of the filler material is to adjust the chemical composition of the molten metal bath and to reduce the sensitivity to hot cracking. In this paper is examined and interpreted the effect of the additive materials selected at the laser welding of some alloys with aluminum base of the 6xxx series on the macro – and the microstructure of the welded joints.

Theoretical Prediction of Structural, Mechanical, and Thermophysical Properties of the Precipitates in 2xxx Series Aluminum Alloy

We presented a theoretical study for the structural, mechanical, and thermophysical properties of the precipitates in 2xxx series aluminum alloy by applying the widely used density functional theory of Perdew-Burke-Ernzerhof (PBE). The results indicated that the most thermodynamically stable structure refers to the Al3Zr phase in regardless of its different polymorphs, while the formation enthalpy of Al5Cu2Mg8Si6 is only -0.02 eV (close to zero) indicating its metastable nature. The universal anisotropy index of AU follows the trend of: Al2Cu > Al2CuMg ≈ Al3Zr_D022 ≈ Al20Cu2Mn3 > Al3Fe ≈ Al6Mn > Al3Zr_D023 ≈ Al3Zr_L12 > Al7Cu2Fe > Al3Fe2Si. The thermal expansion coefficients (TECs) were calculated based on Quasi harmonic approximation (QHA); Al2CuMg shows the highest linear thermal expansion coefficient (LTEC), followed by Al3Fe, Al2Cu, Al3Zr_L12 and others, while Al3Zr_D022 is the lowest one. The calculated data of three Al3Zr polymorphs follow the order of L12 > D023 > D022, all of them show much lower LTEC than Al substance. For multi-phase aluminum alloys, when the expansion coefficient of the precipitates is quite different from the matrix, it may cause a relatively large internal stress, or even produce cracks under actual service conditions. Therefore, it is necessary to discuss the heat misfit degree during the material design. The discrepancy between a-Al and Al2CuMg is the smallest, which may decrease the heat misfit degree between them and improve the thermal shock resistant behaviors.

Metal Matrix Composite Fabricated with 5000 Series Marine Grades of Aluminium Using FSP Technique: State of the Art Review

Aluminium metal matrix composites have been shown to make significant contributions to the area of new materials and have become widely accepted in high-tech structural and functional applications such as those in the aircraft, automobile, marine, mineral, defence, transportation, thermal management, automotive, and sports and recreation fields. Metal matrix composites are manufactured using a variety of manufacturing processes. Stirring casting, powder metallurgy, squeezing casting, in situ processes, deposition techniques, and electroplating are part of the manufacturing process used in the manufacture of aluminium-metal matrix composites. Metal matrix composites that use friction stir processing have a distinct advantage over metal matrix composites that use other manufacturing techniques. FSP’s benefits include a finer grain, processing zone homogeneity, densification, and the homogenization of aluminium alloy and composite precipitates. Most metal matrix composite investigations achieve aluminium-metal matrix composite precipitate grain refinement, treated zone homogeneity, densification, and homogenization. This part of the work examines the impact of reinforcing particles, process parameters, multiple passes, and active cooling on mechanical properties during the fabrication of 5000-series aluminium-metal matrix composites using friction stir processing. This paper reports on the available literature on aluminium metal matrix composites fabricated with 5xxx series marine grade aluminium alloy using FSP.

A comprehensive survey on the cold metal transfer process in welding similar and dissimilar materials and for cladding

The growing use of aluminum in a variety of industries is driving technologists to create practical and effective techniques and processes for joining aluminum alloys. The main aim of this artifact is to critically review and examine the maturity of welding for comparable and differing materials and also for cladding using Cold Metal Transfer. CMT, which stands for Cold Metal Transfer in the acronym, is a modified MIG welding technique. The CMT and its modes are used in similar and dissimilar welding of Al as well as its alloys of 2xxx, 5xxx, 6xxx, and 7xxx series, and with other materials is discussed in detail and compared with other joining methods. The recent advancements in this field with enhanced mechanical properties of Al alloys, as well as high-performance welding techniques, are discussed in this article. The mechanical and microstructural properties of weld like weld strength, microhardness, corrosion behavior, surface morphology, ductility, and fracture mechanism were used to assess the efficiency of the weld. The following aspects of weld bead surface consistency are investigated in terms of bead uniformity along the welding path, bead surface smoothness, and spattering strength. The effort is made to conclude the welding system which is free from all welding flaws, like gas porosity, spattering, and intermetallic formation, resulting in welded joints with the highest mechanical properties. CMT as an advanced welding approach has gained a significant attraction from researchers in investigating it for the cladding process. The geometric and microstructural properties of a clad-like microhardness assessment, and corrosion resistance analyses were used to evaluate the applicability of CMT in the cladding process.

AUSTRAL WRIGHT 5052

Abstract Austral Wright 5052 is a wrought, non-heat-treatable, aluminum-magnesium-chromium alloy (5xxx series) that exhibits a good combination of strength, corrosion resistance, and formability in a wide range of rolled products. It is about mid-way through the series of aluminum-magnesium alloys for alloying content and strength. It has excellent fatigue properties, with an endurance limit of 115 MPa in the H32 temper and 125 MPa in the H34 temper. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Al-492. Producer or source: Austral Wright Metals.

Modeling of Galvanic Corrosion in three-metal Systems Consisting of ZM5 Magnesium Alloy, 6XXX Series Aluminium Alloy and 304 Stainless Steel under Thin Electrolyte Layer by Numerical Simulation, Electrochemical and Salt Spray Test

Modeling of Galvanic Corrosion in three-metal Systems Consisting of ZM5 Magnesium Alloy, 6XXX Series Aluminium Alloy and 304 Stainless Steel under Thin Electrolyte Layer by Numerical Simulation, Electrochemical and Salt Spray Test

Analysis of the Extrusion Process of Aluminium Alloy Profiles

The paper presents an analysis of the results of numerical tests of the extrusion process of structural panels made of the 5xxx and 6xxx series aluminium alloys in a designed split die. The obtained products are intended for innovative superstructures of special car bodies. The main purpose of the research was the designed split die and numerical simulations and analysis of test results to determine the parameters of the extrusion process. The distribution of stress intensity, strain, strain rate, and temperature in the extruded metal was analysed for two different speeds of the punch movement. On the basis of the analysis of the distribution of stress values occurring in the extrusion process, the conditions enabling the real process of extrusion of the panel profile in industrial conditions in the designed split die were determined. It was shown that panel sections can be produced from ingots with a length of 770 mm on a press with a pressure of 35 MN (12").

Towards an alloy design strategy by tuning liquid local ordering: What solidification of an Al-alloy designed for laser powder bed fusion teaches us

High-strength aluminium alloys from the 2XXX, 6XXX, and 7XXX series suffer from severe hot cracking issues during 3D printing. Thus, there is a need to design new alloys with an improved hot cracking resistance while taking advantage of the non-equilibrium processing conditions of laser powder bed fusion to achieve optimized properties. Here, we report the successful fabrication of a new Al-Mn-Ni-Cu-Zr alloy designed for L-PBF. The as-built microstructure was characterized at different scales using synchrotron X-ray nano-tomography and microscopy with a special focus on automated crystallographic orientation mapping (ACOM) in transmission electron microscopy. Based on this multiscale microstructural investigation, we identify various mechanisms involving the presence of a locally ordered liquid during solidification under conditions typical of additive manufacturing. This local liquid ordering is often defined as Icosahedral Short Range Order (ISRO). The multiple consequences of ISRO in the liquid on the hierarchical microstructure inherited from additive manufacturing are discussed. ISRO enables refinement of the grain size thus improving the processability via an increase of the hot cracking resistance, producing equiaxed grains and twinned dendrites contributing to randomizing the crystallographic texture, and possibly extending supersaturated solid solutions through a cage effect. It is concluded that promoting ISRO should be considered a promising pathway to design alloys for additive manufacturing with good processability and optimized properties.

Formation mechanisms of surface blistering in AA6xxx rolled products: microstructure characterisation, ultrasonic analysis, and rolling tests results

ABSTRACT The source of surface blister defect in 6xxx series Al rolled products was studied. A blister defect, aligned with the rolling direction, was observed on the surface of the AA6xxx Al rolled sheets. It was indicated that the porosities and small microstructural inhomogeneities inside the cast ingots, identified by ultrasonic tests and metallography analysis, were not the origin of these surface defects. Pilot scale rolling trials indicated that the blister defects were correlated with the longitudinal internal casting cracks. The short side cracks in the cast ingots, covered by a thin Al oxide layer, were not healed and remained partially open after the rolling process. The unhealed cracks served as the nucleation sites for H2 precipitation during the later stages of the thermomechanical process, which were subsequently resulted from surface blisters on the AA6xxx Al rolled sheets.

Ballistic perforation and penetration of 6xxx-series aluminium alloys: A review

This study evaluates literature on mechanical response of 6xxx series aluminium alloys under dynamic loads (projectile impacts). It is mainly concerned with the ballistic behaviour of 6xxx series Al alloys fabricated through different sample processing routes involving varied heat treatments at elevated, sub-zero and cryogenic temperatures. Failure and deformation mechanisms leading to dynamic fracture have also been considered. Microstructural evolution, wherever available, is incorporated in this study to understand its influence on energy absorption, and deformation and failure mechanisms under ballistic loads. A brief review of analytical and numerical perforation and penetration models for ballistic impact has been attempted too. These approaches have become more sophisticated incorporating compressibility, better material models, and interface friction effects, etc. over the years. The review also includes semi-empirical and empirical equations proposed based on previous experimental data in some works. However, more investigation is needed to ascertain the applicability of these empirical equations. The deficiencies in available work have thereupon been pointed out for future problems.

Local mechanical properties and precipitation inhomogeneity in large-grained Al–Mg–Si alloy

Al–Mg–Si (6xxx series) alloys show excellent mechanical properties due to the precipitates formed during heat treatment. However, heat treatment of these alloys results in a soft precipitation free zone (PFZ) close to grain boundaries that weakens them and promotes fracture, and thereby reduces the ductility of the material. This study provides quantitative insights into the mechanical properties and underlying plasticity behavior of Al–Mg–Si (6xxx series) alloys through combined nanoindentation hardness measurements and in-depth characterization of the microstructure adjacent to the PFZ region and in the grain interior. Experimental nanoindentation, transmission microscopy (TEM) and electron channeling contrast imaging results confirm the weakening effect from PFZ by means of a reduced hardness close to grain boundaries. The nanoindentation hardness mapping also revealed an increase in hardness a few micrometers from the grain boundary with respect to the grain interior. Precipitate quantification from TEM images confirms that the hardness increase is caused by a locally higher density of precipitates. To the authors’ best knowledge, this harder zone has not been recognized nor discussed in previously reported findings. The phenomenon has important implications for the mechanical properties of large-grained (>100 µm) aluminium alloys.

Environment-Induced Cracking of High-Strength Al-Zn-Mg-Cu Aluminum Alloys: Past, Present, and Future

Environment-induced cracking (EIC) during commercial use of aluminum alloys started over 125 y ago (mid-1890s), some 45 y earlier than previously documented, with earliest failures for Al-Zn-Mg-Cu, 7xxx series alloys occurring a decade later. Needs for lighter, thicker, and stronger alloy products, first driven by WW1 and WW2 militaristic requirements and subsequently by relentless demands from modern aircraft industry designers, resulted in major in-service EIC in commercial high-strength Al-Zn-Mg-Cu alloys in the United States and United Kingdom during the 1950s, 1960s, and 1970s. These were avoidable had research findings from France, Germany, and Japan from the 1930s and 1940s been implemented. Unprecedented U.S. Government R&D funding during the late 1960s, 1970s, and early 1980s led to AA7050 and similar alloys, that essentially eliminated EIC issues during commercial usage for several decades. EIC assessment for the following “new-generation” high-strength alloys relied totally on standard ASTM test methods, incapable of providing data directly relatable to the service conditions. Although EIC service issues for the latest generation of 7xxx series alloys remains manageable, the premature appearance of EIC requires a quantitative understanding of EIC initiation under environmental and mechanical conditions directly relatable to intended use, to prevent unexpected failures for future alloys. Directions for future high-strength 7xxx series aluminum alloy development and EIC assessment to provide quantitative data relatable to service conditions and input for structural design and for service life prediction are discussed.