Aluminum Alloys, Processing and Characterization: On-Demand Oral Presentations
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Andre Phillion, McMaster University; Dmitry Eskin, Brunel University

Monday 8:00 AM
March 14, 2022
Room: Light Metals
Location: On-Demand Room

An Advanced Industrial Methodology for Optimizing the Properties and the Process of Homogenization for Extruded AA2xxx & AA6xxx: Simon Rečnik¹; Jožef Medved²; Varuzan Kevorkijan¹; Sandi Žist¹; ¹Impol Aluminum Industry; ²University of Ljubljana, Faculty of Natural Sciences and Engineering
    We have established an industrial methodology for the prediction, formation, transformation and growth of individual phases in the microstructures of aluminum alloys used for the most demanding applications. The thermodynamic calculations of the equilibrium and nonequilibrium states were performed with the Thermo-Calc program, and the microstructure analysis was performed by optical and scanning electron microscopy. X-ray diffraction (XRD) analysis was also used to more accurately identify and confirm the microstructural components. The efficiency of the analytical procedure was tested on selected formable alloys from the 6xxx and 2xxx series (AA 6082, AA 2618 and AA 2024), where we systematically developed or optimized selected product properties. With these advanced thermodynamic and metallographic tools, we can provide our customers with a quality that accords with their requirements and creates economic benefits in the form of higher added value of the finished products and cost savings in the production process.

Correlation between Electrochemical and Standard Testing of Aluminum Alloys: Matjaž Finšgar¹; Irena Lesjak²; Varuzan Kevorkijan²; Marko Degiampietro²; ¹University of Maribor, Faculty of Chemistry and Chemical Engineering; ²Impol Aluminum Industry
     This work reports on a corrosion study of different aluminum alloys of series 2xxx (AA2011, AA2014, AA2024, AA2030, and EN AW 2030) in a 5 wt.% NaCl water solution. The corrosion was investigated using the standard PV113 test and a series of different electrochemical measurements (chronopotentiometry, electrochemical impedance spectroscopy, and cyclic polarization) lasting 72 h. A possible correlation between the maximum penetration depth due to corrosion into the base material, caused by the standard PV113 test, and the time of electrochemical fatigue was investigated. It was found that a linear correlation exists between the penetration depth in the base material and the electrochemical fatigue time for most of the alloys tested. Moreover, a correlation between the electrochemical fatigue methods and the PV113 test exists for materials that were the most susceptible to intergranular corrosion. Furthermore, it was demonstrated that electrochemical fatigue is suitable for inducing intergranular corrosion.

Heat-treatment Response of Al–Mg–Si Alloys with Varying Mg/Si Ratio: Abdul Wahid Shah¹; Seong-Ho Ha²; Young-Ok Yoon²; Shae Kwang Kim¹; ¹UST korea; ²Korea Institute of Industrial Technology
    Al–Mg–Si based casting alloys are considered as promising alloys for automotive applications because of their high strength along with high ductility. Recently, the yield strength of these alloys was tried to enhance through the aging-treatment (T5- temper), which, however, led to only slight increase in the yield strength compared to as-cast condition. However, few studies have been done regarding the response of Al–Mg–Si based alloys to the T6- heat-treatment. The subjecting of these alloys to solution heat treatment (SHT) process can lead to a more saturated solid solution and as a result, enhanced precipitation hardening response is expected. Furthermore, there is also need to study the effects of compositional variation on T6- heat treatment response of Al–Mg–Si based alloys. Therefore, the aim of the current study was to investigate heat-treatment response of Al–Mg–Si alloys with varying Mg/Si ratios.

Through Thickness Localized Strain Distribution and Microstructural Characterization of Functionally Graded Al/GNP Composite Fabricated by Friction Stir Processing: Abhishek Sharma¹; Yoshiaki Morisada¹; Hidetoshi Fujii¹; ¹JWRI, Osaka University
    In the present study, the through-thickness functionally graded Al/GNP composite is fabricated by a novel single-step friction stir processing involving a step grooving approach. The digital image correlation technique reveals a variation in localized yield strength from ~ 44 MPa at the surface to ~ 49 MPa at the core giving a significant variation of ~ 5 MPa within a short span of 2 mm (thickness) indicating the higher stiffness of the core region. The maximum strain value also ranges from ~ 0.79 at the surface to ~ 0.48 at the core of the composite signifying the strain accumulation near the FSP surface. The load transfer through the clean and semi-coherent interface between the GNP and Al matrix seems to have the dominant role in the localized strengthening of the core region. The property gradient indicates that the objective of fabricating the FGC is successfully realized by the proposed methodology.

Precipitation Hardening in Innovative Processing of 6xxx Aluminum Alloys: Alexander Wimmer¹; Annika Haemmerle¹; Calin Marioara²; ¹Neuman Aluminium; ²SINTEF Industry
    From literature, four hardening mechanisms are well known: solid solution hardening, precipitation/dispersion hardening, grain boundary hardening and work hardening. In this study an additional hardening mechanism, cluster harden-ing, was observed. Based on TEM images and strength calculations it has been shown, that contributions from the four “classical” hardening mechanisms are not sufficient to describe the experimental observed strength. This new hardening mechanism and the interaction with work hardening has been analyzed in a large-scale, optimized T8 process, which far exceeds the strength properties of the classical T6 condition. Moreover, the effect of trace elements on precipitation kinetics was studied. Both the effects of wanted trace elements (micro-alloying) and unwanted trace elements (secondary aluminum) were examined.

Evolution of Work Hardening in 6xxx Aluminum Alloys in the Course of Natural Aging Following Continuous Annealing: Christian Bollmann¹; Chengchao Yu²; Mehdi Lalpoor³; Alexis Miroux³; ¹Alvance Germany GmbH; ²RWTH Aachen University; ³Alvance Aluminum Duffel BV
    The formability of Al sheet material is determined by its work hardening behaviour (WHB) up to the onset of strain localization. Under industrial production conditions of a continuous annealing line (CAL), the material undergoes various thermomechanical processing steps which may have an adverse effect on work hardening, i.e. natural aging and pre-aging. To understand the evolution of work hardening in a CAL, the impact of the main post-quench processing parameters of a CAL on the WHB of AA6016 and AA6005 were investigated experimentally by laboratory simulations. Based on the true stress σ - true strain ε curve, the work hardening θ=dσ⁄dε was characterized by the initial work hardening rate θ_0 and the dynamic recovery rate β=dθ⁄dσ. The investigation revealed that both parameters θ_0 and β decrease most in the course of natural aging after solution heat treatment and quenching, but subsequent processing steps also influence the WHB.

Co-extrusion of Dissimilar Al Alloys via Shear Assisted Processing and Extrusion: Mageshwari Komarasamy¹; Scott Taysom¹; Darrell Herling¹; Scott Whalen¹; ¹Pacific Northwest National Laboratory
    Bi-metallic tubes are generally used where two distinct properties are required at the outer and inner part of the tube such as electrical/thermal conductors. In this investigation, shear assisted processing and extrusion (ShAPE) was employed to fabricate bi-metallic tubes from dissimilar Al alloys. Material flow during co-extrusion of dissimilar Al alloys was investigated using micro computed tomography. Detailed microstructural characterization of the interface and various locations of the bi-metallic tubes were carried out using scanning electron and transmission electron microscopy techniques. A defect-free, metallurgically bonded interface between core and shell was observed. Furthermore, hardness and tensile properties of the bi-metallic ShAPE tubes were examined in extruded and heat treated conditions.

Development of a Machine Learning Model to Predict Constitutive Behaviour of Macrosegregated A356 Alloy: Jun Ou¹; Shaul Avraham¹; Daan Maijer¹; Steve Cockcroft¹; ¹University of British Columbia
    Macrosegregation during solidification results in spatial variation of microstructure and mechanical properties in a cast part. This study is aimed developing numerical methods to predict the local constitutive behaviour of A356 aluminum alloy following macrosegregation. Constitutive data was generated from a series of castings with compositional and microstructural variations in the as-cast and heat-treated conditions. Two numerical methods were developed to represent this data: 1) an equation fitting method based on a modified Hollomon equation, and 2) a machine learning technique based on a deep neural network (DNN). The parameters in both methods are trained using the experimentally measured constitutive data. The features (input) of the data includes the silicon content (composition), secondary dendrite arm space (SDAS) (microstructure) and heat-treated condition, and the labels (output) include the yield stress and flow stress as a function of plastic strain. Both methods are capable of making accurate predictions on the constitutive behaviour.

Multi-alloy Aluminum Tubing via Shear Assisted Processing and Extrusion: Brian Milligan¹; Mageshwari Komarasamy¹; Anil Battu¹; Tamas Varga¹; Anthony Guzman¹; Brandon Taysom¹; Darrell Herling¹; Scott Whalen¹; ¹Pacific Northwest National Laboratory
    To promote lightweighting of automotive structures, there is a need for new processing techniques that create a variation in properties within a single component. Customization would enable optimization of mechanical properties such as strength, ductility, and stiffness thereby reducing the need to specify a material or gage thickness for one region that is not needed in another. To this end, Shear Assisted Processing and Extrusion (ShAPE) was used to fabricate tubing having a gradient in alloy composition, and thus performance, along the length. Tubes that transition from 6061, to 7075, and back to 6061 have been extruded with an outer diameter of 12 mm and wall thickness of 1 mm. Morphology of the transition, microstructure, and mechanical properties are reported. The effect of process conditions are be discussed. Additionally, this work represents the first known thermomechanical processing technique whereby 7XXX has been joined without creating a weakened heat affected zone.

Quantification of Plastic Strain in the Precipitate Free Zone of Natural Aged Al-Mg-Si Alloys: Mojtaba Mansouri Arani¹; Xiang Wang²; Nick Parson³; Warren Poole¹; ¹University of British Columbia; ²McMaster University; ³Rio Tinto Aluminium
    The mechanical properties of Al-Mg-Si alloys are linked to their thermomechanical process history. The objective of this study is to provide a quantitative assessment on the effect of quench rate after solution treatment on the strain distribution at the microstructural level using high resolution digital image correlation (HRDIC). The microstructure was characterized using electron back scattered diffraction (EBSD), secondary electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that solute depleted areas formed near grain boundaries are sites for strain localization during deformation.

Solubility Limit of Iron in Aluminum and Its Alloys: Role on Recrystallization, Grain Growth, Texture and Interfacial Segregation Leading to Ductile Failure: Shigeo Saimoto¹; Christopher Gabryel¹; Haiou Jin²; Raja Mishra³; ¹Queen's University; ²Natural Resources Canada; ³University of Waterloo
    Despite the low solubility and diffusivity of iron in aluminum, industrial annealing of wrought aluminum is done at or above 340°C for complete recrystallization. Cube textured aluminum capacitor foils are annealed at ~220°C followed by a second annealing at 530°C. This study addresses the underlying cause behind such practices. Pure aluminum samples were pre-strained to ~25%, annealed at 230°C or higher, cold rolled and recrystallized. Iron solute content after annealing at 230°-300°C was 0.014-0.170 ppm and cold rolled samples recrystallized to ~1 ľm grains at 60°C. Similar studies were done in AA1100, AA6063 and AA5754. The key finding was at 335°C, in all cases, either ultra-fine Al6Fe precipitates formed or pre-existing ones dissolved. The relationship between texture evolution and Fe segregation to grain boundaries resulting in solute and particle drag and to micro-particles that act as nuclei for de-cohesion will be discussed and smart processing guidelines will be described.

Microstructural Evolution of High Zn 7000-series Aluminum Alloy with Addition of Titanium: Kwangjun Euh¹; Jae-Gil Jung¹; Sang-Hwa Lee¹; Se-Hun Kim²; ¹Korea Institute of Materials Science; ²Korea Automotive Technology Institute
    The effects of Ti addition on the microstructural evolution and mechanical properties of high-Zn aluminum alloy were investigated at each process step such as casting, extrusion, solution treatment and aging. Addition of titanium causes refinement of both the grains and bulky η-Mg(Zn,Cu,Al)₂ particles in the as-cast alloys. After hot extrusion, the Ti-added alloy has increased amount of recrystallized grains by particle-stimulated nucleation, decreasing the strength of as-extruded alloy. Titanium addition causes size decrease of L1₂ precipitates and increases the number density of them while substituting Zr site with Ti, that is, (Al,Zn)₃(Zr,Ti). Besides, Al₁₈Mg₃Ti₂ phase is formed by Ti addition during solution treatment, which acts as a heterogeneous nucleation of η precipitate. The strength of the aged alloys is improved by the formation of fine L1₂ precipitates, grain refinement and the refinement of bulky η-phases.

Effect of Post Extrusion Heat Treatment on Mechanical Property of Aluminum Alloy 2024 Tube Produced Using Shear Assisted Processing and Extrusion (ShAPE): Md Reza-E-Rabby¹; Tianhao Wang¹; Daniel Graff¹; Timothy Roosendaal¹; Nathan Canfield¹; Scott Whalen¹; ¹Pacific Northwest National Laboratory
    The present work deals with the Shear Assisted Processing and Extrusion (ShAPE) of AA2024 tubes and strength optimization using commonly applied tempers of T3510 and T8510. The ShAPE process enables extruding AA2024 at an extrusion speed of 7.4 m/min and 480⁰C die temperature, which is otherwise beyond the extrudability limit of this alloy using a conventional extrusion technique. The ultimate tensile strength at different tempers (466 MPa for T3510 and 503 MPa for T8510) exceeds the ASTM/ASM (minimum/ typical) values for the studied tube geometry. In addition, the yield strength for the corresponding tempers (382 MPa for T3510 and 481 MPa for T8510) surpass any reported value in the literature or the highest industrial value. The ductility (% elongation) is also improved due the microstructural refinement and enhanced dispersion of precipitates by the solid phase processing followed by cold working in different temper conditions.

In Situ Processing of Rapidly Solidified Al-33wt%Cu Droplets: Jonas Valloton¹; Najia Mahdi²; Loraine Rabago¹; Hani Henein¹; ¹University of Alberta; ²Norcada Inc.
    Under rapid solidification conditions, Al-33wt%Cu eutectic droplets develop a microstructure composed of two different morphologies: an undulated eutectic, assumed to grow during recalescence, followed by a lamellar eutectic growing post recalescence. In situ heat treatments are applied to Al-33wt%Cu droplets rapidly solidified using Impulse Atomization to investigate the dynamic effect of temperature and time on the two eutectic morphologies. The samples are aged in situ in a SEM using a heating stage developed by Norcada. The undulated region coarsens faster than the regular eutectic, with fine lamellae still visible at 500°C. At 525°C, both regions are indistinguishable from each other. Coarsening rates are evaluated for both regions and compared to established models. At 550°C the droplet is fully liquid, but retains its shape due to the oxide skin. This allows in situ solidification experiments. The resulting eutectic morphologies and spacings are analyzed as a function of the imposed cooling rates.