TH038

What Does Exit Temperature Measurement Tell Us?

Christopher W. Jowett, Rio Tinto Aluminum, Canada; Yahya Mahmoodkhani, University of Waterloo, Canada; Nick Parson and Guillermo Garza, Rio Tinto Aluminium, Arvida R&D Centre, Canada

Exit temperature measurement in 6xxx-Series alloy extrusion is routinely used to ensure the material has reached a sufficiently high temperature to cause dissolution of Mg and Si such that the required mechanical properties can be attained. The other important temperature, not routinely measured, is the die bearing/profile surface temperature, as this dictates the surface quality of the product. It is well established that the latter temperature can be significantly higher than that measured at the platen. This difference is primarily due to the large thermal gradient that exists across the profile thickness as it leaves the die and the subsequent rapid thermal conduction, such that the temperature measured at the profile is an average value. Using a combination of experimental extrusion trials and FE modeling, this paper describes work conducted to understand the complex relation between the surface and bulk exit temperatures during multi-billet runs and how this is influenced by process conditions such as the billet/container temperatures and differentials.

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TH040

Charge Weld Scrap Minimization by Means of Dead Metal Flow Control in Die Design

Tommaso Pinter, Almax Mori & Alumat, Italy; Dan Antonios, Alexandria Industries Mid America, USA; and Barbara Regiani and Andrea Gamberoni, University of Bologna, Department of Industrial Engineering (DIN), Italy

In structural extrusions and other critical sections, charge weld and coring are unacceptable defects. The extension of the charge weld, otherwise called front-end defect, is strongly influenced by the die geometry. It has been shown that, in order to minimize the front-end defect, dies should be designed such that the flow is balanced and the seam weld lines appropriately positioned. The work reported in this paper examines the dynamics of the dead metal zones in hollow extrusion dies through the use of FE analyzes and looks at the effect of their minimization on the front-end defect.

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TH047

Investigation of Material Flow and Thermal Behavior during the Transient Stage of Extrusion

Cunsheng Zhang, Shandong University, People’s Republic of China/Conglin Aluminum Co., Ltd., People’s Republic of China; Shan Yang and Guoqun Zhao, Shandong University, People’s Republic of China; and Anjiang Gao and Lanjun Wang, Conglin Aluminum Co., Ltd., People’s Republic of China

Numerical simulation is an effective means to understand material flow and thermal behavior during the extrusion process, which have a great effect on the product quality. The material flow behavior and temperature evolution are obviously distinct during different stages in an extrusion cycle. However, due to large time consuming with finite element simulation, current literatures mainly focus on the steady-state simulation of extrusion process, which neglect the beginning and the ending stage during an extrusion cycle.

The purpose of this work is to investigate the material flow and thermal behavior during transient extrusion process of a 7xxx-Series aluminum alloy profile. Firstly, the thermo-mechanical model will be built with DEFORM-3D. Then based on the numerical model, the material flow, velocity distribution, temperature distribution, extrusion force, etc. during the entire extrusion cycle will be investigated. Finally, the practical profile will be extruded on an extrusion press to verify the numerical results. This work could provide useful guidance for determining the process parameters of the aluminum profiles.

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TH051

Fundamental Research and Future Developments of Aluminum Extrusion Technology

Pradip K. Saha, The Boeing Company, USA

Continuous development of aluminum extrusion technology is helping to meet the cost of extrusion in the competitive world market. Extrusion manufacturers are facing customer demands for excellent quality and higher productivity with complex product geometry from soft, medium and harder aluminum alloys. Technology is developing progressively in all major areas including billet making, extrusion presses and equipment, die and tooling design, and extrusion process technology. Technology research and development advances in these areas begin with the billet making and preparation and continue to the extrusion process control. This paper will provide some fundamental research on tribology and thermodynamics and their relationship with major extrusion variables and their effects on die performances and extrusion quality. In addition, some useful process variables and their relationships associated with everyday extrusion practices will be provided. This paper will also highlight future plan for developments in various categories of extrusion technology including billet, extrusion press, and die and extrusion process technology to improve productivity, and quality in aluminum extrusion for the customer need.

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TH056

The Effect of Crystallographic Texture on the Mechanical Response of Aluminum Extrusion Alloys

Warren Poole and Jingqi Chen, The University of British Columbia, Canada; Y. Mahmoodkhani and Mary A. Wells, University of Waterloo, Canada; and N.C. Parson, Rio Tinto Aluminum, Canada

The increasing demands for the application of aluminum extrusion alloys to automotive structures requires detailed knowledge on the factors that control the mechanical response. This includes an improved understanding of yielding, work hardening and fracture. A factor that has received little attention in this context is the crystallographic texture of the extrudate. The current study will examine in detail the effect of texture on mechanical properties of AA6082 based alloys that have been processed to produce recrystallized and unrecrystallized alloys. The texture and details of the microstructure have been characterized using electron backscatter diffraction (EBSD) technique and the visco-plastic self-consistent (VPSC) polycrystal plasticity model has been used to predict properties such as mechanical anisotropy. The results show that model predictions are in semi-quantitative agreement with experiments. This presents the opportunity to use models to study how processing affects the final anisotropy of the extruded products.

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TH057

Automated Extrusion Die Design Integrated with Simulation

Nikolay Biba, Micas Simulations Ltd., UK; Sergei Stebunov and Andrey Lishny, QuantorForm Ltd., Russia

The paper presents an attempt to bind extrusion die design and extrusion simulation in a single development and optimization routine. The simulation is based on the Euler-Lagrange approach that is realized as a FE model of the material flow coupled with die deformation. It means that elastic deformation of the die influences the material flow while the die deformation itself is dependent on the contact pressure applied by flowing material. Such a coupled solution is obtained through several iterations and includes automated re-meshing of the material flow domain that is required due to significant distortion of initial mesh in the bearing area. Such simulation coupling is especially important for complex profile shapes because die deflection causes inclination of an initially straight bearing, creating local choke or relief zones that may significantly influence the material flow. As soon as simulation shows some problems like unbalanced material flow, it is necessary to modify the die geometry either in the bearing area or in the portholes or welding chamber. Such modification can be done faster and easier with an automated system of 3D extrusion die design that has been developed. It is based on the idea of parametrisation of basic features of die and mandrel design. The bearing length, depth of pre-chamber, location and shape of webs can be easily modified by just altering some parameters. The modified shape of the die is exported to the simulation program where we can see how efficiently this modification influences the material flow and die deformation. If necessary this routine can be repeated several times to reach the best results. The presented approach is illustrated by examples where different ways of die design alteration have been applied and then tested by simulation and practice.

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TH058

A Special-Purpose FE Simulation Method for Virtual Modelling of Complex Hollow Profile Extrusion Processes

Pavel Hora,, Christoph Becker, and Longchang Tong, ETH Zurich, Switzerland

In the framework of this paper, a specialized ALE-FE-Code is introduced that allows the combined simulation of the filling process of the extrusion die and the subsequent profile extrusion in one single simulation. The method that uses a pre-meshed filled extrusion die is implemented to the IVP FE-code PressForm and avoids any remeshing operations and allows by that a fast computation without problems arising from instable boundary conditions. This is achieved by the premeshing, which enables a precise and geometry-dependent element distribution. The developed method is described in detail and validated; complex extrusion examples of hollow profiles demonstrate the advantages of the proposed simulation strategy.

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TH063

The Effect of Die Design on T-Streak Formation

Jean-François Béland, National Research Council Canada; Nick Parson and Chris Jowett, Rio Tinto Aluminum, Canada

Streaking remains one of the main quality concerns for decorative painted or anodized soft alloy extruded profiles. In many cases the defects are not visible until after the finishing operation, resulting in late delivery and extra cost. There are many causes of streaking, including billet metallurgical quality and extrusion defects but one of the most common streak types is that occurring at T-sections. The inherent local section thickness change can influence the bearing contact condition and the underlying metallurgical structure, both of which can promote streak formation either in terms of the mill finish surface topography or the response to etching. In practice, various methodologies, such as the application of choke or modifications to the feeder pocket design, are often applied in an attempt to control the severity of such streaks. This paper describes the results of extrusion trials conducted to examine the impact of systematic modifications to die design on streaking tendency.

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TH064

Influence of Extrusion Die Bearing Geometry on Surface Grain Structure and Texture

Yahya Mahmoodkhani and Mary A.Wells, University of Waterloo Canada; N.C. Parson, Rio Tinto Aluminum, Canada; and J. Chen and Warren Poole, The University of British Columbia, Canada

The variation in deformation conditions from surface to the center of extrusions often produces heterogeneous grain structures. An example of this is the coarse grain surface layer often found in medium strength alloys which can be detrimental to performance. It is well-known that the die bearing profile, in the form of choke or “Controlled Strain Rate” contours can influence the formation of this layer but the underlying mechanisms are not well understood. The current paper describes experiments conducted to gain insight into the generation of surface microstructures as a function of die bearing geometry. A simple bar was extruded using various die bearing profiles. The resulting surface microstructures were characterized by Electron Backscattered Diffraction (EBSD) and optical microscopy. Comparisons were then made to the thermo-mechanical history and stored energy predictions experienced by the material at different spatial points generated with an FEM model using DEFORM-2D.

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TH072

Friction Behavior in Long Bearing Channels during Aluminum Extrusion; Experimental and Numerical Investigation

Vidal Sanabria and Soeren Mueller, Extrusion Research and Development Center TU Berlin; and Sven Gall, INGWERK GmbH, Germany

The friction force in the bearing channel is related to product speed, temperature, pressure and surface conditions, which define mainly the local flow stress and contact area. Bearing channel configurations such as length and angle also play an important role because they change the hydrostatical conditions and thus, the real friction contact area. Multi-hole extrusion trials have proven that the product speed is highly sensitive to the angle in long bearing channels, but the cause of this effect has not been completely understood. In order to investigate this problem, extrusion trials of aluminum alloy AA6060 were carried out using a four-hole die with interchangeable inserts. The bearing channels had an initial diameter and length of 20 mm, but the angle of the channel was varied from 0.5° opening, parallel, 0.5° and 1° closing. After each experiment the filled inserts were carefully extracted from the die and lengthwise sectioned by means of wire erosion. Posteriorly, the aluminum-steel interface was optically evaluated and the real contact length measured. Numerical analyzes considering full and partial bearing contact length, as well as different friction models, were carried out and compared with experimental results.

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TH078

Modeling the Effect of Mn on Extrudability, Mechanical Properties and Grain Structure of AA6082 Alloys

DTrond Furu 1, Rune Østhus 2, Nadia Telioui 3, Regine Aagård 4, Magnus Bru 4, and Ole Runar Myhr 5
1 Norsk Hydro ASA, Corporate Technology Office, Norway, 2 SINTEF Raufoss Manufacturing, Norway, 3 Hydro Aluminium, Customer Technical Support, Norway, 4 NTNU, Department of Material Science and Engineering, Norway, 5 Hydro Aluminium, Research and Technology Development, Norwayy

The present paper demonstrates the effect of manganese (Mn) in 6082-type alloys on extrudability, as-extruded grain structure, and mechanical properties by the use of Through Process Modeling (TPM). In order to separate the effect of Mn in dispersoids and Mn in solid solution, a rather comprehensive experimental program was designed including six different levels of Mn (0-1.2 wt%) within the 6082 window, and two specific homogenization cycles prior to extrusion and mechanical testing. The TPM methodology includes physical-based microstructure models for precipitation of Mn-dispersoids and MgSi-phases, as well as models for generation of deformation and recrystallization structures in combination with finite element (FE) simulations of the extrusion process. The input parameters to the TPM models comprise the chemical composition of the alloys and the processing parameters from casting, homogenization, extrusion, and annealing to the final artificial aging. Comparisons between simulation results and measurements have confirmed the ability of the present TPM methodology to predict changes in extrusion forces, grain structures, and mechanical properties without any tuning or calibration of the modeling parameters.

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TH079

Experimental and Numerical Investigation on Friction Behavior for Simulation of Extrusion Processes

Dong-Zhi Sun, Andrea Ockewitz and Florence Andrieux, Fraunhofer Institute for Mechanics of Materials IWM, Germany

Extrusion processes are essentially influenced by friction between billet and extrusion tools. Process optimization as well as the microstructure and mechanical properties of extrudates depend strongly on friction effects. An accurate description of the friction is a key point in extrusion simulation. The use of common tests like pin-on-disk for the characterization of friction effects in extrusion processes is not always relevant because the loading situation is different from that in extrusion with typically high hydrostatic stress levels. In this work, a two-step friction test was developed. This experimental method enables a systematic variation of normal stress, temperature and velocity. These friction tests with cylindrical specimens are limited to small plastic deformation. To enable larger plastic deformation during the test, an alternative test setup was suggested. The geometries of the die and specimen were optimized. All friction tests were simulated with the FE code HyperXtrude to analyze the loading situations and a modified shear friction model was derived based on the experimental results. The predicted flow pattern and friction forces were compared with the experimental results. Both relevance to real extrusion processes and predictability of the friction behavior by numerical modeling were demonstrated.

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TH095     

Multi-Goal Virtual Optimization of Industrial Extrusion Dies

Barbara Reggiani, Lorenzo Donati and Luca Tomesani, University of Bologna, Department of Industrial Engineering (DIN), Italy

In the design of complex extrusion dies, a number of different and potentially conflicting goals are involved in process optimization, such as profile tolerances, mechanical properties, aesthetical surfaces and die life. Thus, a robust and comprehensive approach to investigate the problem is required that must also be compatible with the industrial timing. In this context, the aim of the present work was to perform a multi-objective virtual optimization of industrial porthole dies for the maximization of the profile quality (welds and flow balance), of the production rate (velocity) and of the die strength. Two industrial profiles were investigated: a thick round tube manufactured with a three-leg porthole die, selected as a starting point to define, fix and validate the procedure. As second step of the work, the response surface methodology was applied to extrapolate analytical input-output correlations and subsequently adopted as single input of the optimization procedure to solve a more complex industrial case of hollow profile.

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TH096

Extrusion of Tailored Seamless Aluminum Tubes with Axial Variable Wall Thickness and Characterization of Mechanical Properties

Maik Negendank, Ugur A. Taparli, Soeren Mueller and Walter Reimers, Technische Universitaet, Berlin, Germany

Customers from the automobile and aviation industries demand lightweight constructions of increasing strength and rigidity in order to reduce weight and CO2 emissions of transportation vehicles. For some applications these needs can be met by load adapted (tailored) profiles. Load adapted profiles are characterized by a higher wall thickness in sections with higher acting loads, whereas less stressed areas can be designed with reduced wall thickness. In the current investigation tailored AA6060 and AA6082 hollow profiles with axial variable wall thickness were extruded at different billet temperatures and ram velocities. The wall thickness variation is achieved by changing the inner profile diameter. The applied extrusion process for manufacturing of tailored hollow profiles is described and characterized. Furthermore, the microstructure evolution along the profile’s length was analyzed revealing fibrous, partly recrystallized or fully recrystallized microstructures. Three point bending tests of profiles with varying lengths of thick-walled section revealed that the increased wall thickness section can be significantly reduced and thus profile weight be saved without significantly losing load capacity.

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TH104

Production of Hollow Profiles by Hot Extrusion of Aluminum Chips

Matthias Haase and A. Erman Tekkaya, Institute of Forming Technology and Lightweight Construction, TU Dortmund University, Germany; and Wojciech Z. Misiolek, Institute for Metal Forming, Lehigh University, USA

Aluminum alloy machining chips can be directly recycled into semi-finished profiles by hot extrusion without previous remelting and casting. For this approach, the aluminum machining chips are cleaned from remaining lubricants, compacted to chip-based billets and extruded at elevated temperatures to chip-based extrudates. In this paper, the feasibility of producing chip-based hollow profiles with a conventional porthole die is investigated. Cast material is processed similar to the chips in order to produce conventional extrudates as a reference. The mechanical properties and the microstructure of the chip-based finished parts are analyzed and compared to the extruded cast material. In addition, a numerical simulation of the extrusion process is conducted in order to analyze the pressure and strain affecting the chips during the extrusion process, as those are the critical factors to achieve sound bonding between the individual chips.

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TH108

Influence of Extrusion Die Geometry on Weld Seam Properties of AA6082 Extrudates

Martin Schwane, Matthias Haase, and A. Erman Tekkaya, Institute of Forming Technology and Lightweight Construction, TU Dortmund University, Germany; and Wojciech Z. Misiolek, Institute for Metal Forming, Lehigh University, USA

Direct hot extrusion of aluminum is an established process to produce a great variety of semi-finished parts for applications in many different industries. Porthole dies are used for the production of hollow section profiles. Due to the presence of the legs supporting a bridge, seam welds are formed in the extruded profiles. Seam welds may have inferior mechanical properties compared to the base material, which can be a critical issue when the profiles are exposed to high service loads or subsequent forming steps. Several criteria for the prediction of the seam weld quality have been proposed in literature. However, there is still a lack of understanding regarding the local extrusion welding phenomena within the welding chamber. Therefore, a special test die was developed, which allows the experimental investigation of the seam weld formation along the welding zone inside the extrusion die. In addition, finite-element simulations were conducted to gain deep understanding of the relation between material flow, the evolution of state variables and the seam weld properties. Finally, the influence of the process parameters on the seam weld quality was investigated both numerically and experimentally.

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TH111

Using FEM to Model and Troubleshoot Extrusion Die Failures

Mike A. Foster Deepu Joseph, Scientific Forming Technologies Corp., USA; and Tushar Bakhtiani, Kelby Graham, and Paul Nolting, VIP Tooling, USA

Process modeling software based on the finite element method (FEM) is a valuable tool for analyzing extrusion processes. Material flow during the extrusion can be analyzed, giving insight into the initial transient behavior in the die, weld seam formation, etc. Stresses in the die components can also be obtained using simulation, allowing alternate die designs to be analyzed. Several techniques can be used to simulate the stresses in extrusion dies. Decoupled analyzes model the extrusion using rigid dies, and then a subsequent stress analysis is run where the tools are switched from rigid to elastic. This provides the stresses in the tools at one particular instance in time. A second technique is coupled die stress analysis, where the tools are elastic during the extrusion analysis. This type of simulation is much more computationally intense, but it provides the stresses in the tools during the entire extrusion process. In this paper, coupled die stress analyzes are run in DEFORM-3D to study the cracking of a die component that was designed to elastically deflect during the extrusion process. The root cause of the fracture is identified and a modified die design is investigated.

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TH114

Prediction of Thermal Conditions in Rod Extrusion by FEM-Analysis for Laboratory and Industrial Aluminum Extrusion

Henry S. Valberg and S.T. Khorasani, Norwegian University of Science and Technology, Department of Engineering Design and Materials, Norway; D. Nolte, SINTEF, Materials and Chemistry, Department of Materials and Structural Mechanics, Norway; and W.Z. Misiolek, Lehigh University, Institute for Metal Forming, USA

The software Deform has been used to model axisymmetric aluminum rod extrusion. The FEM-models are able to describe fine details regarding thermal heating of the billet material during extrusion and how the main extrusion parameters affect the temperature build-up during the extrusion cycle, as well as material cooling effects to the tooling. The paper will pay special emphasis on the heating conditions in the shear zone formed inside the billet during the extrusion stroke, and in addition, the high temperature rise occurring in the deformation zone ahead of the die orifice. A comparison will also be made with respect to the extent a small size laboratory extrusion process will have thermal conditions corresponding to those commonly obtained in large size industrial extrusion.

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TH115

Required Extrusion Loads in Axisymmetric Rod Extrusion Characterized by FEM Analysis with Experiments

Henry S. Valberg and S.T. Khorasani, Norwegian University of Science and Technology, Department of Engineering Design and Materials, Norway; D. Nolte, SINTEF, Materials and Chemistry, Department of Materials and Structural Mechanics, Norway; and W.Z. Misiolek, Lehigh University, Institute for Metal Forming, USA

A large number of extrusion experiments have been performed in a laboratory press in order to measure how the extrusion load is affected by various extrusion parameters such as extrusion speed, reduction ratio, and temperature difference between billet and tooling for two different aluminum alloys. After this, the software Deform was used to model these processes. Good agreement has been obtained between the simulations and the experiments. The paper will discuss how the extrusion parameters affect the required load and how FEM-analysis can be used to predict loads in the case of industrial size extrusion.

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TH123

Extrusion-Machining as an Analog to Investigate the Deformation Zone Mechanics during the Aluminum Extrusion Process

Daniel R. Klenosky, Andrew Kustas, David Johnson, and Kevin Trumble, Purdue University, USA

Extrusion-machining combines cutting with simultaneous extrusion using an additional constraining tool to induce very large and well-characterized effective strains. Accurate analytical models exist for the extrusion-machining process to calculate values of effective strain, strain rate, and temperature rise in the deformation zone as a function of processing parameters. The extrusion-machining process is therefore useful as an analog to explore the deformation mechanics of conventional aluminum extrusion, since local processing conditions are otherwise impossible to measure. This process is used in conjunction with finite element models to investigate the effects of individual variables on the material response of 6xxx-Series and 7xxx-Series aluminum alloys during the conventional extrusion process. Results of this work are shedding light on the microstructural evolution seen during extrusion, specifically relating to the surface recrystallization that causes the peripheral coarse grain defect.

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TH126

Experimental Investigations and Numerical Simulations of Textures and Microstructures of Extruded Aluminum Alloys

Kai Zhang, Norwegian University of Science and Technology, Norway; Antonio Segatori, SAPA Technology, Sweden; Trond Aukrust, SINTEF Materials and Chemistry, Norway; Jesper Friis and Tanja Pettersen, SINTEF Materials and Chemistry, Norway; and Christian O Paulsen, Bjorn Holmedal and Knut Marthinsen, Norwegian University of Science and Technology, Norway

The microstructures and textures in a commercial AlMgSi alloy after extrusion of a solid round profile have been experimentally and numerically investigated. Several trials of extrusion were performed at different extrusion temperatures and ram speeds. The butt end and the die were water quenched after extrusion with short delay time. Microstructures of the quenched butt ends and profiles have been measured by optical metallography and the SEM-EBSD technique. Deformation or fully recrystallized microstructures have been observed, depending on the extrusion conditions. By coupling FEM flow simulations and crystal plasticity models, the deformation crystallographic textures after extrusion have been predicted. The recrystallized extrusion microstructures are then simulated using the analytical recovery and recrystallization model AlSoft. The quality of simulations is assessed by the experimental results.

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TH163

Effect of Extrusion Microstructure on Corrosion of AA6005A Aluminum Alloy

Daniel Seguin and Calvin L. White, Michigan Technological University, USA; Richard Dickson and Eskild Hoff, Hydro Aluminum Technology Center, USA

The rate of intergranular corrosion (IGC) penetration along the extrusion direction in AA6005A was observed to decrease with exposure time when immersed in a low-pH saltwater environment. Characterization of the local environment within simulated corrosion paths revealed that a pH gradient existed between the tip of an IGC path and the external. Knowledge of the local environment within an IGC path allowed development of a simple model based on Fick’s first law that considered only mass diffusion of Al3+ away from the tip of an IGC path. The predicted IGC penetration rate agreed well with the observations. These results suggest that the IGC penetration rate in AA6005A extrusions is ultimately limited by the diffusion of Al3+ produced by an anodic reaction at the tip of an IGC path.

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TH199

Development and Validation of a Dynamic and Static Recrystallization Model for Microstructural Prediction of AA6060 Aluminum Alloy with Qform

Claudia Bandini, Barbara Reggiani, Lorenzo Donati and Luca Tomesani; University of Bologna, Italy

The aim of the present work is to develop a unified model to predict the grain evolution of 6-Series aluminum alloys, during deformation and subsequent dynamic and static recrystallization, and validate it by use of Qform, a Lagrangian FE Code. Experimental data were obtained from two previous backward extrusion campaigns (AA6060-O and AA6082-O), that were performed at different conditions of temperature and strain rate. All the specimens were subjected to microstructural analysis in terms of grain size evaluation, before extrusion (initial grain size), after extrusion (evaluation of dynamic recrystallization) and after heat treatment (evaluation of a fully static recrystallization). The model is implemented through user defined routines; batches of simulations were carried out for each material in order to fit the best parameters that determine the final grain size at 100% of recrystallization material through comparison between numerical results and experimental grain size. Through the experimental data it was possible to validate the theoretical model for the grain size and shape evolution during dynamic recrystallization, obtained from previous numerical simulations.

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