Al-Mg Alloy Research Articles

Study of microstructure evolution in the aluminum‒magnesium alloy AlMg6 after explosive welding and heat treatment

Study of microstructure evolution in the aluminum‒magnesium alloy AlMg6 after explosive welding and heat treatment

The influence of Zn addition on the microstructure and mechanical and corrosion properties of warm rolled Al[sbnd]Mg alloys containing Er and Zr

The effects of a minor Zn addition on the mechanical and corrosion properties and microstructure of a high Mg content AlMg alloy containing Er and Zr in the warm-rolled state were studied using tensile test, nitric acid mass loss test (NAMLT), exfoliation corrosion susceptibility test (ASSET), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The tensile test results showed that the 0.58 wt% Zn addition to the Al-Mg-Er-Zr alloy increased the yield strength from 297 to 351 MPa and tensile strength from 416 to 445 MPa, but decreased the elongation from 13.3 % to 12.5 %. The NAMLT and ASSET results showed that the two warm rolled alloys were initially in the stabilization state, but the Al-Mg-Er-Zr alloy without Zn added became sensitized severely after the accelerated sensitization annealing (ASA) at 100 °C. The Zn addition improved the intergranular corrosion (IGC) resistance and exfoliation corrosion (EC) resistance significantly. The TEM results showed that, for the Al-Mg-Er-Zr alloy, there were Al3(Er,Zr) phase particles in the matrix and β (Al3Mg2) phase particles separated from each other at the grain boundary. After the ASA treatment, more β phase particles were precipitated and covered the grain boundary completely. For the Al-Mg-Zn-Er- Zr alloy, another nanoscale T (Al32(Mg, Zn)49) phase was precipitated in the matrix, and there were no grain boundary phase particles observed at the grain boundary, because the precipitation of T phase consumed the supersaturated Mg in the matrix, thus suppressing the formation of grain boundary phase particles during the ASA treatment and resulting in a good corrosion resistance. The strengthening effect of the Zn addition was mainly due to the formation of T phase particles during the warm rolling process.

Effect of Ce and Zr on the microstructure and mechanical properties of high-Mg content Al-Mg alloy

Al-7Mg alloy with different Ce and Zr additions were hot and cold rolled to investigate the effects of chemical composition and rolling route on the microstructure and mechanical properties of high-Mg content Al-Mg alloys. The Ce and Zr additions led to the formations of Al11Ce3 and Al3Zr phases in Al-7Mg alloy, and the Zr atoms can be absorbed into the Al11Ce3 phases. The Al11Ce3 phases can be refined by rolling, and the fragmented Al11Ce3 and Al3Zr precipitate phases enhanced the density of dislocations in the studied alloys during rolling. The Al11Ce3 and Al3Zr phases promoted the grain refinement of hot-rolled Al-7Mg-Ce-Zr alloys, but some coarse grains were obtained in the Zr-containing alloys after cold rolling. The rolled alloys with 0.2Ce and 0.25Zr additions own higher second phase and dislocation strengthening effects than the Al-7Mg and Al-7Mg-Ce alloys with the same state, and the yield strengths of the hot-rolled and cold-rolled Al-7Mg-0.2Ce-0.25Zr alloys reach to 242 MPa and 499 MPa, respectively. Furthermore, the ductility of the cold-rolled Al-7Mg-0.2Ce-0.25Zr alloy was improved by its bimodal grain structure.

Synchrotron scanning transmission x-ray spectro-microscopy (STXM) characterisation of β-SiC nanowhisker AZ91 magnesium alloy nanocomposites

β-SiC nanoparticles are one of the most common reinforcements in Mg-Al alloy matrix nanocomposites (MgMNCs). The interfacial interactions between β-SiC and the alloy matrix are complex due to the occurrence of new phases and the fine scale of the 3D architecture. This study aims to explore the feasibility of using synchrotron Scanning Transmission X-ray spectro-Microscopy (STXM) to investigate such interfacial interactions and acquire reference X-ray Absorption Spectroscopy (XAS) data for some common interphase crystals present within the composites, which are not readily available. Throughout this study, a reliable procedure for collecting STXM data on samples derived from MgMNCs was developed, and reference XAS spectra for α-Mg, β-Mg17Al12, T2-Al2MgC2, Mg2Si and MgO present in MgMNCs were collected. The accessibility of STXM and spatially resolved XAS spectrum is not only useful for nanocomposite alloy research but applicable widely across the magnesium alloy research community when identifying and quantifying the phases with complex crystal structures and oxide states.

Research Progress on the Microstructure Evolution Mechanisms of Al-Mg Alloys by Severe Plastic Deformation.

Al-Mg alloys are widely used as important engineering structural materials in aerospace engineering, transportation systems, and structural constructions due to their low density, high specific strength, corrosion resistance, welding capability, fatigue strength, and cost-effectiveness. However, the conventional Al-Mg alloys can no longer fully satisfy the demands of practical production due to difficulties caused by many defects. The high strength of Al-Mg alloys as non-heat treatment precipitation-strengthened alloys is achieved primarily by solid solution strengthening along with work hardening rather than precipitation strengthening. Therefore, severe plastic deformation (SPD) techniques can be often used to produce ultrafine-grained structures to fabricate ultra-high strength aluminum alloys. However, this approach often achieves the strengthening of material at the cost of reduced ductility. This paper comprehensively summarizes the various approaches of ultrafine/nanocrystalline materials for enhancing their plasticity, elaborates on the creation of a bimodal microstructure within the alloy, and discusses the formation of a nanotwin microstructure within the alloy and the incorporation of dispersed nanoparticles. The mechanisms underlying both the strengthening and toughening during large plastic deformation in aluminum alloys are summarized, and the future research direction of high-performance ultrafine crystalline and nanocrystalline Al-Mg aluminum alloys is prospected.

Influence of surface pre-deformation on the Portevin-Le Chatelier effect and the related multiscale complexity of plastic flow in an Al-Mg alloy

The influence of the surface pre-deformation on jerky flow caused by the Portevin-Le Chatelier (PLC) effect was investigated using flat tensile specimens of an Al-Mg alloy. Although jerky flow represents a macroscopic plastic instability, the underlying mechanisms stem from self-organization of dislocations, which pertains to deformation processes at mesoscopic scales. To provide a comprehensive approach, the investigation was carried out by coupling tensile tests, digital image correlation and acoustic emission techniques, each targeting a particular range of scales. Thin superficial layers were pre-deformed using surface mechanical attrition technique (SMAT). It was found that the observed effects depend on which surfaces are processed. Overall, the treated samples exhibited an enhanced yield strength without deterioration of ductility in comparison with the initial material. These changes in the general mechanical behavior are likely to be correlated with the changes in jerky flow. Using digital image correlation, a tendency to delocalization of bursts of plastic flow was found for both the PLC bands and smaller-scale strain heterogeneities outside the bands, the latter having been little studied so far. Unexpectedly, SMAT occurred to modify plastic flow drastically at this scale. In addition to clarification of the role played by the surface in the PLC effect, these findings provide new insights into relationships between deformation processes at distinct scales.

Role of spark energy and frequency on wire-EDM performances of Al-2Mg alloy and Al-2Mg/20 Al3Fe composite: a comparative study

ABSTRACT The performance of wire-electric discharge machining (WEDM) method is inevitably affected by the electric spark. A comparative study is presented related to the influences of spark energy (SE, 1.68–8.40 mJ) and spark frequency (SF, 12.82–15.15 kHz) on machining responses of Al-2Mg/20 vol.% in-situ Al3Fe composite with respect to Al-2Mg alloy. Such comparison is scanty in the literature. Machining performances were measured concerning material removal rate (MRR), cutting speed (CS), and surface roughness (SR) apart from the morphological evolution of machined surfaces. Irrespective of machining condition (for instance, at SE of 5.04 mJ), composite exhibited lower CS (1.27 mm/min), MRR (4.20 mm3/min), and SR (4.42 µm) due to the insulating effect of reinforcement than alloy (i.e. 1.70 mm/min, 5.81 mm3/min, and 4.82 µm, respectively). For both alloy and composite, all three machining performances increased linearly with rising the SE and SF, although the influence of SE was more pronounced over SF. With increasing SE, the difference in the magnitudes of CS and MRR between alloy and composite widened, while the same for SR narrowed. Formations of micro-cracks, lumps of debris, craters, and re-solidified layers were observed more on alloy machining surface than composite; these features enlarged with increasing SE and SF.

Revealing the intergranular corrosion mechanism of AA5083 alloys through experiments and atomic-scale computation

Continuously exposure to elevated temperature, known as sensitization, can accelerate the precipitation of the electrochemically active β phase (Al3Mg2) at grain boundaries (GBs) in Al-Mg alloys. This results in intergranular corrosion (IGC), which seriously affects the application of Al-Mg alloys in marine environments. Low-angle GBs (< 15°) are considered to restrict the nucleation and growth of the β phase, while high-angle GBs (> 15°) can promote these processes. However, the quantitative relationship between GB misorientation and IGC sensitivity at atomic scale is unknown. Herein, the underlying mechanism of IGC in AA5083 alloys with β phase and GB misorientation is investigated by experiments and simulation. The experimental results show that after sensitization when the misorientation angle exceeded 22.6°, the density of the β phase at GBs reaches up to 50 %–60 %. The hybrid molecular dynamics/Monte Carlo algorithm was utilized to simulate the diffusion of Mg and cluster formation in Al-5Mg alloy with 11 different GB models at 300 and 425 K. The maximum GB misorientation angle insensitive to IGC is about 18.9° to 22.6°. However, at 425 K, this angle decreases to 16.3°, increasing the IGC risk of Al-5Mg alloys. The calculation results provide valuable quantitative guidance for the corrosion resistance design of Al-Mg alloys.

Combustion and energy performance of multiple aluminum-based alloy particles

The long ignition delay time, high ignition temperature and agglomeration prevent the aluminum (Al) particles from fully releasing the chemical energy stored within them during combustion. Al-based alloy fuels with high energy density and excellent combustion performance have become a potential candidate for replacement with pure Al. Therefore, understanding the combustion and energy performance of Al-based alloys is beneficial for the development of Al-based energetic materials. Herein, the combustion and energy performance of pure Al and three Al-based alloys were comparatively investigated by means of a thermal analysis system, an ignition and combustion test apparatus, and a variety of physicochemical property characterizations. The results showed that all three Al-based alloys contained at least one intermetallic compound. Al-boron (B) and Al-magnesium (Mg)-B alloys had higher theoretical energy densities than pure Al, while Al-Mg did not. The thermal oxidation properties of all three alloys were significantly better than those of pure Al. Compared with pure Al, the three alloys showed higher burning rate, shorter ignition delays, more vigorous combustion, and higher burnout at room pressure in air. This is still true after adding AP. According to the compositions of the condensed combustion products, the possible chemical reactions during the combustion of the alloys were speculated. Grasping the combustion mechanisms of the alloys is challenging due to the relative lack of thermodynamic data on intermetallic compounds. Finally, a comprehensive comparison of the combustion processes of pure Al and alloys was made. Although the Al-Mg alloy does not have the same theoretical energy density as pure Al, the more outstanding combustion performance and fewer two-phase flow losses may make up for the gap in theoretical energy density.

Transitioning of deformation mode in bicrystalline Al-Mg alloy with Σ3 [1 1 1] 60° {11 8 5} faceted grain boundary

In this letter, the authors have elucidated the effect of alloying biocompatible and lighter magnesium (Mg) solute atoms in a bicrystalline aluminium (Al) solvent incorporated with a faceted coherent-incoherent grain boundary (GB) to analyze the tensile deformation mechanisms. Cryogenic temperature and high strain rate conditions were imposed through molecular dynamics simulations to report the detrimental effect of Mg addition on the tensile strength of Al-Mg alloys. Evidence of transitioning in deformation modes for pure Al and Al-Mg alloys was seen. On elaborating, for pure Al, GBs acted as the dislocation nucleation site; whereas for Al-Mg alloy, it was both the GBs and grains. It was observed that stacking faults (SFs) originated from GBs and propagated toward grains in Al. In contrast, in Al-Mg alloys, SFs were generated simultaneously from both GBs and grains. This simultaneous nucleation of dislocations and SFs from both GBs and grains renders bicrystalline alloys lower the elastic limit than pure metal. Conversely, beyond this elastic limit, the alloys exhibit higher flow stress than the pure metal due to the Mg-dislocation interactions. These findings offer valuable insights for tailoring the mechanical properties of Al-Mg alloys to meet aerospace, automotive and marine engineering-related application requirements.

A novel method simultaneously eliminating Portevin-Le Chatelier effect and enhancing strength in non-heat-treatable Al-Mg alloys

This study investigates the effects of cyclic plasticity on the tensile properties of AA5083 alloys. The low strength and Portevin-Le Chatelier (PLC) effect in Al-Mg alloys means they have found limited use in automotive outer panels. This work shows that by applying cyclic strengthening approach to AA5083, a high density of Mg-Al clusters can be formed in matrix resulting in increased yield and tensile strengths. Moreover, the introduction of cyclic plasticity also effectively suppresses the PLC effect, which is due to the formation of the clusters and the consequent reduction in the number of free Mg atoms in the solid solution. This method introduces the concept of particle strengthening in Al-Mg alloys without altering composition, while simultaneously eliminating the PLC effect. It suggests a potential path for using 5xxx series alloys in applications traditionally dominated by 6xxx series alloys, with added benefits for recycling and sustainability in the automotive industry.

Resolving localized geometrically necessary dislocation densities in Al-Mg polycrystal via in situ EBSD

The distribution of geometrically necessary dislocation (GND) densities is critical to understanding the heterogeneous plastic deformation at intragranular scales in polycrystals. In this work, we performed an in situ electron backscatter diffraction (EBSD) measurement during the tensile test on a polycrystalline Al-Mg alloy. The EBSD patterns were processed through the integrated digital image correlation algorithm to enhance angular resolution. Based on the Nye dislocation density tensor, GND densities of 18 dislocation types in fcc crystals were resolved and mapped at macroscopic strains ranging from 5% to 16%. The evolution of GND distribution showed that GNDs were generated near grain boundaries at small strains and later localized at grain interiors along subgrain boundaries and slip bands at large strains. The inhomogeneous increase in GND densities of different dislocation types, representing dislocation substructures, along the subgrain boundaries was disclosed. Meanwhile, high GND densities were observed along the slip bands when a double noncoplanar slip system was activated inside the grains. The obstructed movement of dislocations by Lomer junctions explained the GND storage in different {111} slip planes. The existence of Lomer junctions was proven by Burgers circuit analysis with high-resolution transmission electron microscopy, which explained the increase in [101] screw dislocation density according to the dislocation reaction.

Investigation of complex single-walled intersecting structures fabricated by wire-arc directed energy deposition

PurposeThis study aims to investigate an intersecting single-walled structure fabricated using wire-arc directed energy deposition (waDED). Because of the highly complex geometrical features of this structure, characterisation is used to identify potential weak points and provide a benchmark for future complex components.Design/methodology/approachA structural component with a process-specific design is built using additive manufacturing of an Al-Mg alloy and analysed using micro-computed tomography. Scans are carried out at different resolutions and subsequently compared to microsections. The chemical composition and hardness are also examined. These investigations provide an enhanced understanding of defects and overall quality of the manufactured parts.FindingsThe results show that very high-quality parts can be achieved using ER5183 alloy, even in intersecting areas. Defects in these regions are primarily caused by converging and diverging waDED paths and discontinuous waDED operations.Originality/valueIn addition to demonstrating the feasibility of complex structures using waDED, this study provides an overview of problem areas and potential improvements in waDED manufacturing.

Investigation of open air and under water laser surface texturing on surface roughness and wettability of Al-Mg alloy

Aluminum-Magnesium (Al-Mg) alloy is widely used in aerospace and marine related applications due to its high corrosion resistance, tensile strength and ductility properties. However, due to hydrophilic nature, its applications are restricted in areas where water absorption may cause problems like corrosion. In this research work, high speed laser texturing was carried out on Al-Mg alloy (AA5754) to improve hydrophobic properties of the material surface. Four different types of pattern, namely lines, grids, concentric circles and concentric rectangles were created on the material surface using a nanosecond fiber laser. Scanning speed was varied at two levels i.e., 500 mm/s and 1000 mm/s. Line density of texture designs was also varied at two levels of 10 lines per mm and 15 lines per mm. The texturing process was carried out in two different processing environment namely open air and in underwater condition. Distilled water with 1 mm thickness above the surface was used during underwater texturing condition. Surface morphology, surface roughness and wettability of all the surfaces were studied for all the experimental conditions. It was observed that lower scanning speed of 500 mm/s resulted in higher values of surface roughness and contact angles. Also, larger texture density leads to lower surface roughness and contact angles for all the pattern designs. Among all the studied texture patterns, grid structures, textured at 500 mm/s of scanning speed resulted in largest surface roughness and surface hydrophobicity.

Surface enhancement on TIG welded dissimilar Al-Mg alloy with ER5356 and scandium composites filler rod

Surface enhancement on TIG welded dissimilar Al-Mg alloy with ER5356 and scandium composites filler rod

Surface Modification of AM60 Mg-Al Alloy with Vanadium and V2O5 Sputtered Deposits: Activity in Marine Ambience

Vanadium (~450 nm) and V2O5 (~350 nm) were deposited by DC magnetron sputtering on an AM60 substrate to improve its degradation resistance in marine ambience. According to Raman and XPS analysis, the vanadium nanofilm mainly consists of amorphous V2O3, while V2O5 comprises two sheets of VO5 and VO4 units. After 30 days of immersion of the coated AM60 in a marine model solution (SME), the shift of the pH of the SME to more alkaline values was less pronounced for V2O5-AM60 because of the HCl acid formation during the partial dissolution of V2O5 in the presence of NaCl, and thus, a higher concentration of Mg2+ ions ~100 mg L-1 was released from the Mg (AM60) matrix. The lower concentration of ~40 mg L-1 from the V-AM60 surface was attributed to the possible intercalation of the released Mg ions (cations) into the conductive tunnels of V2O3 as the main component of the vanadium sputtered deposit. This oxide has been reported as a material for high-capacitive energy storage. In this way, the V-deposit provided longer partial protection for the AM60 surface (Mg matrix) from localized pitting attacks.

Machinability of gas metal arc based 3D printed Al-Mg 5356 alloy using wire-EDM

Wire-Arc Additive Manufactured (WAAM) is relatively new method of metal 3D printing in which the raw material is heated by the gas metal arc and the molten metal pool is deposited layer-by-layer using a computer numerically controlled axis drive system. Since WAAM needs a finishing process for attaining the final dimensions of the components, there is a need to investigate the machinability aspects of WAAM fabricated materials. This work investigates the machinability of Al-Mg 5356 alloy test samples fabricated by WAAM process using wire-electric discharge machining (Wire-EDM). The test samples were subjected to Wire-EDM and the obtained material removal rate (MRR), kerf width (KW) and surface roughness (Ra) were investigated at different Wire-EDM process settings of voltage, current, pulse-on time (Ton), pulse-off time (Toff) and wire speed (Ws). Statistical analysis revealed that current had a significant influence on MRR. Ton had a strong influence on KW and Ra, whereas Toff exhibited a considerable impact on all these responses. Notably, Ws demonstrated a significant impact on Ra. However, voltage was found to have statistically negligible impact on all the machining responses. Microstructural investigations and compositional analysis were conducted providing valuable information on the cut surfaces. The results derived from the present investigation are useful for predicting the optimum process parameter settings for machining of WAAM-based 3D printed Al-Mg alloy in various manufacturing industries.

The thermodynamic effects of solute on void nucleation in Mg alloys.

Replica exchange transition interface sampling simulations in Mg-Al alloys with high vacancy concentrations indicate that the presence of a solute reduces thermodynamic barriers to the clustering of vacancies and the formation of voids. The emergence of local minima in the free energy along the reaction coordinate suggests that void formation may become a multi-step process in the presence of a solute. In this scenario, vacancies agglomerate with solute before they coalesce into a stable void with well-defined internal surfaces. The emergence of vacancy-solute clusters as intermediate states would imply that classical nucleation theory is unlikely to adequately describe void formation in alloys at high vacancy concentrations, a likely precursor for alloy strengthening through nanoscale precipitation.

Influence of the Plastic Deformation Process on the Residual Stresses and Hardness of an Al-5Mg Alloy.

The service behavior of ductile metallic materials, when they have previously undergone technological plastic deformation, depends on the deformation conditions. These are represented, among others, by the deformation rate, the process temperature, the applied pressures, and the introduced stresses, as well as other process variables. The investigation of the mechanical properties obtained after plastic deformation is an important means that contains two characteristics: on the one hand, to determine to what extent the parameters of the technological manufacturing process influence the main characteristics of the final component; and, on the other hand, on the basis of these characteristics, to analyze whether the component subjected to plastic deformation will be able to function reliably and safely. In the present work, an experimental study was made of the residual stresses developed and hardnesses obtained both in the immediate vicinity of a highly plastically deformed area and in an area previously obtained by rolling, without additional plastic deformation. For the determination of the residual stresses, the tensiometric rosette drilling method was used. By determining the same quantities in a non-plastically deformed area, significant changes in the values of the two quantities in the plastically deformed area were found. An increase in the maximum principal normal stresses by approx. 60 MPa and an increase in the Rockwel hardness by approx. 10 HRC was found. A sample was taken from the area under a plastic deformed circular shape, and was analyzed microscopically.

Portevin-Le Chatelier behavior in AlMgScZr alloys: Effects of Al3(Sc,Zr) dispersoid distribution and grain structure

Plastic instability caused by the Portevin-Le Chatelier (PLC) effect remains a challenge for Al–Mg alloy sheets during shape-forming processes, as it causes unsightly stretcher-strain markings on the surface of final products. In this study, the PLC behavior in annealed AlMg and AlMgScZr alloy sheets with varying Al3(Sc,Zr) dispersoid distributions and grain structures were investigated by combining tensile tests, microstructural characterization, and DIC analysis. The results show that the presence of Al3(Sc,Zr) dispersoids can inhibit the PLC effect, which is manifested by a decrease in serration amplitude, PLC band velocity, and an increase in critical strain. The inhibition effect is shown to be highly related to the distribution of Al3(Sc,Zr) dispersoids and resultant grain structures. The alloy with the densest dispersoid distribution and finest subgrain structure showed the slightest PLC effect. The reduction in serration amplitude and PLC band velocity is ascribed to the augmented resistance to local strain softening, caused by inhibition of dislocation motion by Al3(Sc,Zr) dispersoids and subgrain boundaries. In addition, a high density of Al3(Sc,Zr) dispersoids can strongly trap vacancies, which is responsible for the increase in critical strain.