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Material constitutive behaviour and microstructure study on aluminium alloys for friction stir welding
Get PDFThe material constitutive behaviour and microstructure of Aluminium alloys 6082
and 7449 were studied with the Gleeble hot compression test. The novel aspect of
the work is that the testing was done at high strain-rates and at temperatures
within 5 K of the solidus. The results indicated that the strength was
maintained up to near solidus temperatures, with no dramatic strength reduction
being observed. There was however, a distinct change in the slope observed with
the 7449 results around 720 K. The experimental results were then fit to the
Zener-Holloman equation, which describes the relationship between the material
flow stress, temperature and strain-rates. The material microstructure of the
hot compression test samples was analysed, and the averaged grain size was
calculated to compare with friction stir weld nuggets. This will be used to
infer the processing conditions that exist in the dynamically recrystallized
weld nugget. Finally, a simple model was used to understand how processing
conditions affected the deformation behaviour
Corrosion characteristics and mechanism of 6082/AZ31/6082 laminated metal composites in tropical marine atmospheric environments
No full textThe preparation of Al/Mg/Al laminated metal composites (LMCs) by lamination technique can well combine the good corrosion resistance of Al alloy and the lightweight characteristics of Mg alloy. In this paper, the atmospheric corrosion behavior and underlying mechanism of 6082/AZ31/6082 LMCs with and without side exposure for one year of filed exposure to the tropical marine atmospheric environment were investigated. The results showed that the corrosion rates of AZ31 and 6082 and LMC-C were 55.967, 1.167, and 0.925 g m−2·a−1, respectively. The microstructure of the Al layer on the surface of LMCs underwent a significant transformation, characterized by a noticeable grain refinement and a concomitant increase in dislocation density. Moreover, the potential disparity between the second phase (AlMnFeSi and Mg2Si) and the matrix was diminished. These findings collectively contribute to the enhanced resistance of 6082/AZ31/6082 LMCs to intergranular corrosion and pitting corrosion. However, the accelerated dissolution of the intermediate Mg layer, facilitated by the galvanic corrosion effect during field exposure of the LMCs, resulted in a 4.5-fold increase in corrosion-induced mass loss. Notably, the ultimate tensile strength of the LMCs exhibited insensitivity to field exposure duration, while their plasticity underwent a gradual decline. This comprehensive study elucidates the corrosion behavior and underlying mechanisms of 6082/AZ31/6082 LMCs subjected to a tropical marine atmospheric environment, providing valuable insights for the rational design and development of LMCs with enhanced comprehensive performance
Effect of temperature and frequency on the viscoelastic behavior of commercial 6082 (Al–Mg–Si) alloy
Get PDFThe viscoelastic response of pure Al and commercial 6082 and 6082-T6 (Al–Mg–Si) alloys is measured with dynamic-mechanical analyzer as a function of temperature (ranging from 35 to 425ºC) and loading frequency (ranging from 0.01 to 100 Hz). The measured data (the storage modulus, loss modulus and mechanical damping) are compared to available transmission electron microscopy and differential scanning calorimetry data, to ascertain whether unexplained variations of the viscoelastic behavior of the alloys can be correlated to phase transformations. The results suggest that some of these variations may be controlled by formation and dissolution of metastable phases, such as Guinier-Preston (GP) zones and phases ß”, ß’ and B’. Indeed, GP zones and phase ß” have been reported to control other mechanical properties. However, due to the high complexity of the ageing path of Al–Mg–Si alloys, with formation and dissolution reactions of many precipitate types overlapping along wide temperature intervals, further research is necessary to establish unequivocally the contribution of each individual phase transformation to the overall viscoelastic behavior. Finally, an internal friction peak related to grain boundary sliding is significantly smaller in the alloys compared to pure Al, probably because the precipitates pin the grain boundaries.Peer ReviewedPostprint (author's final draft
Thixoforging experiments with 6082 extrusion feedstock
No full textThixoforming of wrought aluminium alloys, which are relatively more difficult to form in the semisolid state, almost always employs thermomechanically processed billet. This limits the size of the feedstock and, by adding an extra step in the production cycle, is not attractive cost-wise either. An attempt was made in the present work to use 6082 billets for thixoforging without prior thermomechanical processing to improve the competitiveness of this emerging technology in the manufacture of wrought aluminium parts. The primary phase morphology in the 6082 billet has transformed completely into a non-dendritic one upon isothermal heating in the semisolid state. The slugs machined from the 6082 billet were successfully thixoforged after they were isothermally heated at 645 degrees C for 5 min. Further processing to the T6 temper has produced a hardness of 95 +/- 3 HB in the thixoforged parts. While the temperature of the isothermal heating step was slightly higher with respect to the extruded 6082 billets, thixoforging of an aluminium part directly from a DC-cast 6082 billet offers considerable cost savings and is thus much more attractive. (c) 2007 Elsevier B.V. All rights reserved
Thermal properties analysis of aluminium alloy 6082
Get PDFAluminijeva zlitina 6082 je poznana po svoji odlični odpornosti proti koroziji, ter sodi v srednji trdnostni razred med vsemi aluminijevimi zlitinami.
V okviru diplomske naloge smo izmerili toplotne lastnosti aluminijeve zlitine 6082 pri sobni temperaturi, in sicer toplotno prevodnost, specifično toploto in temperaturno prevodnost. Toplotne lastnosti so bile izmerjene v litem, raztopno žarjenem in umetno staranem stanju. Vzorec je bil izpostavljen toplotni obdelavi pri različih temperaturah in časih raztopnega žarjenja, ter umetnega staranja.
Meritve so bile opravljene z metodo tranzientnega planarnega toplotnega vira na napravi TPS Hot Disk 2200, proizvajalca Hot disk AB, po standardu ISO 22007-2.
V delu so opisane tudi definicije toplotnih lastnosti, najpogostejše metode merjenja toplotnih lastnosti, označevanje aluminijevih zlitin ter lastnosti in standardne metode toplotne obdelave aluminijeve zlitine 6082.Aluminum alloy 6082 is known for its excellent corrosion resistance and belongs to the middle strength class among all aluminum alloys.
As part of the diploma thesis, we measured the thermal properties of aluminum alloy 6082 at room temperature, namely thermal conductivity, specific heat, and thermal conductivity. Thermal properties were measured in as-cast, solution annealed, and artificially aged state. The sample was subjected to heat treatment at different temperatures and times of solution annealing, and artificial aging.
Measurements have been performed according to the ISO 22007-2 standard by the method of transient planar heat source on the device TPS Hot Disk 2200, manufactured by Swedish company Hot disk AB.
The paper also describes the definitions of thermal properties, the most common methods of measuring thermal properties, designation of aluminum alloys, mechanical properties, and standard methods of heat treatment of aluminum alloy 6082
Optimization of billets production from high-quality aluminum alloy 6082
Get PDFAluminijeva zlitina AA 6082 se uporablja za različne namene v gradbeništvu, strojništvu, avtomobilski industriji ipd. Dolgoletne izkušnje uporabe zlitine AA 6082 v komercialne namene so pokazale, da je ta zlitina odporna na vremenske vplive brez zaščitnih prevlek. V proizvodnem procesu izdelave zlitine na kvaliteto končnega izdelka vpliva veliko faktorjev in sicer: delež založenega primarnega in sekundarnega aluminija v talilno peč, obdelava taline, čiščenje taline v peči, udrobnjevanja taline, čiščenja taline izven peči, procesnih parametrov pri litju in pogojev homogenizacije drogov.
Primerjali smo meritve in rezultate preiskav iz dveh šarž aluminijeve zlitine AA 6082 pred in po predelavi livnega sistema. Za karakterizacijo preiskovane aluminijeve zlitine AA 6082 visoke kvalitete in doseganje ustrezne mikrostrukture na drogovih premera 228 mm so bile opravljene naslednje meritve in preiskovalne metode: temperaturne meritve, kemijska analiza, termodinamična simulacija faznih ravnotežij (ThermoCalc), diferenčna vrstična kalorimetrija (DSC), optična mikroskopija in elektronska mikroskopija. Ugotovili smo, da je za doseganje ustrezne mikrostrukture po celotni dolžini droga zlitine AA 6082 potrebno zagotoviti višjo temperaturo taline na začetku litja. Namen magistrskega dela je bil izdelava drogov zlitine AA 6082 dolžine 7000 mm z minimalnim izmetom, oziroma znižanje tehnološkega izmeta, kar pomeni boljšo stroškovno učinkovitost in konkurenčnost na trgu. To lahko dosežemo z dodatnimi izolacijskimi pokrovi, ki imajo na spodnji strani električne grelce.The aluminum alloy AA 6082 is used for various purposes in the construction industry, mechanical engineering, automotive industry, etc. Many years of experience in the application of the alloy AA 6082 commercial purposes have shown that this alloy is resistant to weathering without protective coatings. In the production process of manufacturing aluminum alloy AA 6082 on the quality of the final product is influenced by many factors, namely: what is the proportion of stocked primary and secondary aluminum into the melting furnace, what is the treatment of the melt, what is the treatment of the melt in the furnace, modification agent added to the melt, how is the cleaning of the melt outside the furnace, what are the parameters of the casting process and the conditions under which the billets are homogenized.
We compared the measurements and the results of investigations of two batches of cast aluminum alloy AA 6082 before and after the remodeling of the casting system. For the characterization of the investigated aluminum alloy AA 6082 of high quality and to achieve appropriate microstructure on billets of 228 mm diameter the following measurements and investigation methods were used: temperature measurement, chemical analysis, thermodynamic simulation of phase equilibria (ThermoCalc), differential scanning calorimetry (DSC) optical microscopy and electron microscopy. We have found that to achieve the appropriate microstructure over the entire length of the rod alloy AA 6082 it is necessary to provide a higher temperature of the melt at the start of the casting. The purpose of the master’s thesis was to casting billets alloy AA 6082 length 7000 mm with minimal ejection, which means better cost efficiency and market competitiveness. This can be achieved by additional insulating covers having the electric heaters at the lower side
Comparison of the Heat Treatment Response of Wrought and SSM-HPDC Alloy 6082
No full textThe natural and artificial aging responses of wrought and SSM-HPDC alloy 6082 are compared. It is shown that the heat treatment response of this Al-Mg-Si alloy is not influenced by differences in microstructures produced by different processing routes. Wrought alloy 6082 is known to experience an unfavourable effect of prior natural aging on the subsequent artificial aging response, which was also found for SSM-HPDC 6082 in this study. The tensile properties of SSM-HPDC 6082-T6 agree well with those specified for wrought 6082-T6, except for a much lower ductility of the SSM-HPDC variant.</jats:p
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