Aluminium Alloy Hot Direct Extrusion Process Simulation and Surface Defects Analysis

Diplomsko delo obsega izdelavo virtualnega modela preoblikovalnega procesa iztiskavanja aluminijeve zlitine, z namenom določitve tehnološko procesnih parametrov, ki vplivajo na končno stanje površine. Neželeni pojavi pri iztiskavanju aluminijevih zlitin so napake na površini, ki onemogočajo uporabo in znižujejo končni izplen preoblikovalnega procesa. V teoretičnem delu naloge je podan uvod v iztiskavanje aluminijevih zlitin, termomehanska teorija preoblikovalnega postopka, zasnova modela po metodi končnih elementov, teoretično ozadje procesnih map, nastanek napak, temperaturni in torni model iztiskanja, ter teoretično ozadje limitnih diagramov. Jedro diplomskega dela je eksperimentalni del prenosa teoretičnih osnov v numerični model, izdelan s programskim paketom Abaqus, ter obdelava rezultatov simulacij s programskim paketom MATLAB. Spreminjanje radija prehoda čelne ploskve v preoblikovalno območje je bilo uporabljeno za optimizacijo geometrije orodja z numeričnimi modeli. Dodatno so bili spreminjani tudi vhodni procesni parametri, kot sta temperatura predgretja surovca zlitine in hitrost pomika bata stiskalnice, ki povzroča iztiskanje zlitine skozi matrico. Izdelane procesne mape, sestavljene iz map porabe energije in map nestabilnosti so bile uporabljene pri interpretaciji rezultatov numeričnih simulacij. Interpretacija rezultatov numeričnih simulacij je poleg procesnih map podprta tudi z limitnim diagramom izdelanim za virtualno stiskalnico nazivne moči 55 MN, ter aluminijevo zlitino AA 7475. Na podlagi numeričnih simulacij, procesnih map in limitnega diagrama je bila ocenjena uspešnost procesa, ter izdelan limitni diagram, Limitni diagram simulacij predstavlja nižje vrednosti vrha, pri katerem imata limitni krivulji presečišče. Hkrati se v področju nižjih hitrosti pomika bata, širi področje stabilnosti površine, ki je v primeru limitnega diagrama realnega procesa ožje.Diploma work is based on virtual model simulation of hot direct extrusion of aluminium alloy in order to determine process parameters that affect state of extruded surface. Surface defects in the extrusion of aluminium alloys prevent the use of extrudate and reduce the final yield of the forming process. Theoretical part of diploma work includes an introduction to extrusion of aluminium alloys, thermomechanical basis of extrusion forming process, formulation of the finite element method, theory of process maps, extrusion defects, temperature and friction models used in simulation of extrusion and theoretical basis of limit diagrams. Kernel of experimental work presented the implementation of theoretical basis and laws to the numerical model made with Abaqus simulation software and data processing of the obtained simulation results with MATLAB. Geometry of the die models varied along the radii between flat die surface and die bearing, as did the input process parameters such as preheating temperature and ram speed. Simulation results were evaluated with the use of process maps consisting of power dissipation maps and instability maps. In addition to process maps the interpretation of the simulation output data was evaluated by limit diagrams made for a virtual direct press of nominal load 55 MN extruding the billet made of aluminium alloy AA 7475. The simulation limit diagram represented lower peak values, where the limit curves of press and surface intersect, at the same time predicting stability of surface at lower ram speed and higher preheat temperatures in contrast with limit diagram of given alloy

Heat treatment simulation of aluminium alloy hot extrusion process

Magistrsko delo obsega analizo simulacijskih rezultatov predgretja surovcev, gašenja in ohlajanja surovcev pred iztiskavanjem. Omenjeni postopki so neposredno povezani s preoblikovalnim postopkom iztiskavanja aluminijevih zlitin. S postopkom iztiskavanja v vročem se v splošnem izdelujejo palice, cevi in profili. Predhodna priprava, ter njena simulacija, kar predstavlja toplotno obdelavo predgretja, gašenja in ohlajanja surovcev oziroma okroglic pred iztiskavanjem omogoča ogrevanje materiala na temperaturo iztiskavanja, prisilnega raztapljanja zlitinskih elementov iz intermetalnih faz v osnovi mikrostrukture, ter vpliva realnega stanja odvoda toplote iz ogrevanega materiala pred iztiskavanjem. Toplotna obdelava po iztiskavanju obsega gašenje iztisnjenih palic oziroma profilov, kar predstavlja začetno stanje za nadaljnjo naravno ali umetno staranje, t.j. proces izločevalnega utrjevanja. Toplotna obdelava pred in po iztiskavanju v veliki meri vpliva na lastnosti materiala, mikrostrukturno in mehansko, kot posledično tudi na lastnosti same palice oziroma profila. V ta namen se v magistrskem delu obravnava simulacija predgretja, gašenja in ohlajanja surovcev pred iztiskavanjem. S simulacijo toplotne obdelave po metodi končnih elementov je omogočen vpogled v temperaturno polje po surovcu pred iztiskavanjem. Natančnost modela in rezultatov simulacij je podkrepljena z meritvami dejanskih vrednosti temperature na stiskalnici. Na podlagi realnih rezultatov se simulacijski model popravi z adjustažo parametrov in kalibracijo simulacijskih modelov, do dosega dejanskih vrednosti.Presented master\u27s thesis focuses on analysis of simulation results of aluminium alloy extrusion billet preheating and spray cooling simulations. Mentioned processes are directly connected to the bulk metal forming processing named hot extrusion. The main products of hot aluminium alloy extrusion are rods, tubes and profiles. Pre-processing and the simulation of pre-processing, which is considered as a pre-extrusion heat treatment of preheating, spray cooling and general cooling, provides the ability to heat the material to extrusion temperature, dissolve of intermetallic phases and the effect of heat transfer to and from the preheated material before the extrusion process takes place. Post-extrusion heat treatment includes water quenching of extruded material, which sets basis for further natural or artificial ageing. Both mentioned contribute to mechanical properties due to precipitation hardening effect. Heat treatment pre- and post-extrusion processing greatly affects the properties of the material, both microstructural and mechanical properties, subsequently also the properties of extruded product. The master\u27s thesis\u27s focuses on simulations of preheating, spray cooling and cooling of the billet material pre-extrusion. Pre-extrusion heat treatment finite element method simulations provide broader information of the temperature field on the surface and inside the billet. The model accuracy is be supported with result of temperature measurements, performed before the extrusion. Calibration of models is carried out with the adjustment of the main process parameters in order to achieve realistic response of the simulation models

Cold Rolling Technology Optimization for EN AW 4343/3003/4343 Cladded Aluminum Alloys and Influence of Parameters on Microstructure, Mechanical Properties and Sustainable Recyclability

The present study investigates the accumulative roll bonding process applied to the EN AW 3003 aluminum alloy, serving as a composite material on both sides and consisting of the EN AW 4343 aluminum alloy. For the characterization of the optical microscopy, corrosion tests with saltwater acetic acid and mechanical properties before and after the braze test were employed. The numerical simulations accurately predicted the industrial cold rolling values for the rolling force and surface temperature. The most comprehensive understanding of the cold rolling parameters for both side-cladded materials was achieved by combining predictions for cladded and uncladded materials. The thickness of the cladded layer presented as a percentage after roll bonding was 18.7%. During the cold rolling and annealing, the cladded thickness was increased to 24.7% of the final 0.3 mm of the total cold-rolled product thickness. According to the performed braze test for final thickness, the ultimate tensile strength and yield strength were decreased, and the elongation increased to 18.1%. In addition to the described changes in mechanical properties, the material’s anisotropy improved from 5.4% in the cold-rolled condition to 2.0% after the braze test. After multiple re-meltings of the cladded material, the analyzed chemical compositions allow for recycling and reuse as different 4xxx, 5xxx, and 6xxx alloys