Numerical predicting of recycling friendly wrought aluminium alloy compositions

The model presented in this work enables the design of optimal (standard and non-standard "recycling-friendly") compositions and properties of wrought aluminium alloys with significantly increased amounts of post-consumed scrap. The following two routes were modelled in detail: (i) the blending of standard and non-standard compositions of wrought aluminium alloys starting from post-consumed aluminium scrap sorted to various degrees simulated by the model; and (ii) changing the initial standard composition of wrought aluminium alloys to non-standard "recycling friendly" ones - with broader concentration tolerance limits of alloying elements, without influencing the selected alloy properties, specified in advance

Numerical predicting of recycling friendly wrought aluminium alloy compositions

The model presented in this work enables the design of optimal (standard and non-standard “recycling-friendly”) compositions and properties of wrought aluminium alloys with significantly increased amounts of post-consumed scrap. The following two routes were modelled in detail: (i) the blending of standard and non-standard compositions of wrought aluminium alloys starting from post-consumed aluminium scrap sorted to various degrees simulated by the model; and (ii) changing the initial standard composition of wrought aluminium alloys to non-standard “recycling friendly” ones - with broader concentration tolerance limits of alloying elements, without influencing the selected alloy properties, specified in advance

Synthesis and characterisation of ultra-hard and lightweight AlMgB14-xTiB2 composites for wear-resistance and ballistic protection

As an alternative to mechanical alloying, high temperature synthesis (HTS) of ultra-hard, super-abrasive AlMgB14 was performed under normal pressure. The reaction mixture consisted of elemental Al and B, whereas Mg was added in the form of a Mgprecursor which liberates elemental magnesium approximately 400 ºC above the melting point of Mg, in this way reducing its evaporation during heating-up. 95 wt % conversion to AlMgB14 and 5 wt % to MgAl2O4 was achieved. The synthesized AlMgB14 baseline powder, as well as mixtures of AlMgB14 consisting of 30, 50 and 70 wt% of TiB2, were hot pressed to near theoretical density. The various samples produced were characterized for microstructure and hardness. A microhardness of 29.4GPa in hot pressed AlMgB14 and a maximum Vickers hardness of 30.2 GPa in hot pressed samples of AlMgB14 reinforced with 70 wt% of TiB2 particles (d50=4,1 µm) was achieved. Future project milestones necessary for achieving a higher AlMgB14 reaction yield, reducing the MgAl2O4 content and producing sinter-active AlMgB14 powder, as well as hot pressed composites processing improvement for gaining maximum hardness are also presented

The non-destructive prediction of the aluminium content in pressed skulls of aluminium dross

During production of primary and secondary aluminium, various amounts of aluminium dross, a mixture consisting of molten aluminium metal and different oxide compounds, is skimmed per tonne of molten metal. In order to preserve the maximum aluminium content in hot dross for further extraction, it is necessary to cool the dross (e.g. by pressing) immediately after skimming. During pressing, the skimmed dross is transformed into so-called pressed skulls, convenient for storage, transport or further inhouse processing. Pressed skulls, which represent a valuable source of aluminium, are generally valued on a free-metal recovery basis. Therefore, it is important and useful to develop a method of fast and cost-effective non-destructive measurement of the free aluminium content in pressed skulls, independent of the technology of pressed skulls recycling. Following the theoretical considerations presented in this work, a practical industrial methodology was developed for non-destructive prediction of the amount of free aluminium in pressed skulls, wAl, based on non-destructive measurement of the density, ρ, of the pressed skulls

Synthesis and characterisation of ultra-hard and lightweight AlMgB14–xTiB2 composites for wear-resistance and ballistic protection

As an alternative to mechanical alloying, high temperature synthesis (HTS) of ultra-hard, super-abrasive AlMgB14 was performed under normal pressure. The reaction mixture consisted of elemental Al and B, whereas Mg was added in the form of a Mgprecursor which liberates elemental magnesium approximately 400 ºC above the melting point of Mg, in this way reducing its evaporation during heating-up. 95 wt % conversion to AlMgB14 and 5 wt % to MgAl2O4 was achieved. The synthesized AlMgB14 baseline powder, as well as mixtures of AlMgB14 consisting of 30, 50 and 70 wt% of TiB2, were hot pressed to near theoretical density. The various samples produced were characterized for microstructure and hardness. A microhardness of 29.4GPa in hot pressed AlMgB14 and a maximum Vickers hardness of 30.2 GPa in hot pressed samples of AlMgB14 reinforced with 70 wt% of TiB2 particles (d50=4,1µm) was achieved. Future project milestones necessary for achieving a higher AlMgB14 reaction yield, reducing the MgAl2O4 content and producing sinter-active AlMgB14 powder, as well as hot pressed composites processing improvement for gaining maximum hardness are also presented

Proizvodnja in uporaba izkovkov iz Al-zlitin

In this report the production and use of forged aluminium parts are described and the automobile and other principal markets for forged aluminium componnts are outlined.V delu opisujemo proizvodnjo in področja uporabe aluminijastih odkovkov s poudarkom na njihovi uporabi v avtomobilski industriji

Raziskave stabilnosti suspenzije keramičnih delcev v Al in Mg talinah

The rejection of Si3N4,Mg3N2, AlN and Si particles from different slurries consisting of molten aluminum and magnesium alloy with 10% of silicon or pure molten metals was experimentally investigated by measuring changes in the electrical resistance of the slurries before and after rejection occurred. In stirring experiments, only individual powder fractions which passed through a 45 µm sieve screen and remained on a 30 µm screenwere applied. The experiments showed that the rejection of Si3N4 particles from Al-10%Si and Mg-10%Si melts occurs when more than 17-18 vol.% of the ceramic phase is dispersed into the melt, while in pure Al and Mg molten metals spontaneous rejection occurs at 7-8 vol.% of the introduced ceramic phase. A similar tendency of rejection (at 16-18 vol.% of particulate in slurry) was also observed during the introduction of silicon particles into Al-10%Si and Mg-10%Si melts.Preučevali smo stabilnost suspenzij ▫$Si_3N_4$▫, ▫$Mg_3N_2$▫, AlN in Si delcev (sejalna frakcija med 30 in 45 ▫$mu$▫m), dispergiranih v raztaljenem aluminiju in maagneziju ter v talinah iz Al in Mg zlitin z 10% silicija. Izločanje delcev iz talin smo eksperimentalno ugotavljali s pomočjo sprememb električne prevodnosti taline. Ugotovili smo, da prihaja do izločanja ▫$Si_3N_4$▫ in Si delcev iz raztaljenih Al in Mg zlitin z 10 vol.% silicija šele, ko koncentracija delcev v obeh talinah doseže 16-18 vol.%. V primeru talin iz čistega aluminija in magnezija se ▫$Si_3N_4$▫ delci večinoma izločijo, ko njihova koncentracija doseže 7-8 vol.% Za razliko od tega se delci AlN in ▫$Mg_3N_2$▫, ne glede na to, ali so dispergirani v raztaljeni Al in Mg zlitini z 10% silicija ali v čisti kovini, spontano izločijo pri koncentraciji keramične faze, ki praviloma ne presega 4 vol.%. Različno stabilnost suspenzij keramičnih delcev v Al in Mg talini smo skušali pojasniti z reaktivnostjo med raztaljeno kovino in dispergiranimi delci oz. s kemijskimi reakcijami do katerih prihaja na meji med keramično fazo in talino

Carbothermal synthesis of submicrometer [beta]-SiC powder using double precursor reaction mixture

Carbothermal synthesis of submicrometer beta-SiC powder using double precursor reaction mixtur

The economics of converting aluminium wastes into valuable and environmentally friendly products

V delu obravnavamo postopke recikliranja aluminijevih zlitin iz odpadnega aluminija in aluminijeve žlindre s pretaljevanjem v rotacijski peči konvertorskega tipa, ogrevani z gorilnikom na zemeljski plin in kisik. Opisani so trije postopki pretaljevanja odpadnega materiala: klasični, "mokri" postopek z dodatkom soli v razmerju 1:1 glede na vsebnost nealuminijskih sestavin v odpadnem materialu, "suhi" postopek z dodatkom soli 0,6:1 glede na nealuminijske sestavine v odpadnem materialu in postopek pretaljevanja brez dodatka soli, ki se večinoma uporablja le za pretaljevanje aluminijeve žlindre. Osnovni problem, ki se pojavlja pri vseh treh postopkih recikliranja aluminijevih zlitin iz odpadnega aluminija in aluminijeve žlindre je predelava stranskih produktov pretaljevanja odpadnega materiala v koristne in okolju neškodljive izdelke oz. surovine za nadaljnjo uporabo. Pri "mokrem" in "suhem" postopku gre za predelavo t.i. "slanega kolača", pripostopku pretaljevanja brez dodatka solipa za predelavo "nekovinskega ostanka". Opisani so in ekonomsko ovrednoteni različni postopki recikliranja soli iz "slanega kolača" in predstavljeni možni postopki nadaljnje predelave "nekovinskega ostanka".The advanced aluminum-alloy recycling procedures, based on remelting of aluminum scrap and aluminum dross in a tilted rotary barrel furnace equipped with a multi-purpose oxy-fuel-based combustion system have been evaluated. These are: the "wet" process, in which typically 1 kg of salt flux is added to 1 kg of non-aluminum constituents of scrap and dross, the "dry" (low-salt) process, which uses 40% less salt flux compared to the "wet" process, and the "salt-free process", which is promising for the recovery of aluminum from aluminum dross. The common problem in all of above-listed procedures is an appropriate divertion of the recycling wastes produced by aluminum recycling in a variety of commercially valuable and environmentally friendly products. The "wet" and "dry" processes generate a so-called "salt cake", which consists of aluminum metal, spent salt flux and residue oxides while the"salt-free process" produces only residue oxides. Different procedures for salt recovery from salt the cake were described and the economics associated with these scenarios were evaluated. Moreover, various possiblities for the conversion of residue oxides into valuable products were listed and the economics associated with additional processing of residue oxides were also evaluated

Recikliranje gnetnih aluminijevih zlitin iz nizkocenovnih vrst metalurško čistega odpadnega aluminija

In the recycling of wrought aluminium alloys from lower grades of scrap (metallurgically clean but highly contaminated with non-metallic impurities) the following two tasks were identified as the most demanding: (i) achieving the required final chemical composition of an alloy with a minimal addition of primary aluminium and alloying elementsand (ii) keeping the level of impurities (inclusions, hydrogen, trace elements and alkali metals) in the molten metal below the critical level. Because of the lack of chemically based refining processes for reducing the concentration of alloying and trace elements in the molten aluminium, once the concentrations of these constituents in the melt exceed the corresponding concentration limits, the only practical solution for their reduction would be an appropriate dilution with primary metal. To avoid such a costly correction, carefully predicting and ensuring the chemical composition of the batch in the pre-melting stage of casting should be applied. Fortunately, some of the impurities, like hydrogen and alkali metals, as well as various (mostly exogeneous) inclusions, could be successfully reduced by employing existing refining procedures. In this work, (i) the state-of-the-art technologies, including some emerging technical topics such as the evolution of wrought alloys toward scrap-intensive compositions, monitoring of the content of organics in the incoming scrap and the quality of molten metal achieved by different smelting and refining technologies, and (ii) the relevant economic advantages of the recycling of wrought aluminium alloys from the lower grades of scrap are reported. By analyzing the market prices of various grades of scrap and the total cost of their recycling, the cost of aluminium ingots made from recycled aluminium was modelled as a function of aluminium and the alloying-element content in the incoming scrap. Furthermore, scrap mixtures for producing aluminium wrought alloys of standard quality from lower grades of scrap and with a significant new added value were illustrated.Pridobivanje recikliranega aluminija standardne kakovosti iz nizkocenovnih virov bo v prihodnje odločilno vplivalo na konkurenčnost in uspešnost evropske aluminijske industrije. Pri recikliranju gnetnih aluminijevih zlitin iz nizkocenovnih vrst odpadnega aluminija (metalurško čistih, vendar onesnaženih z nekovinskimi nečistočami) sta posebej zahtevni naslednji dve tehnološki nalogi: (i) zagotavljanje želene kemijske sestave aluminijeve zlitine ob minimalnem dodatku primarnega aluminija in legirnih elementov in (ii) ohranjanje nivoja nečistoč (vključkov, vodika, elementov v sledovih in alkalijskih kovin) v talini v mejah dovoljenega. Ker koncentracijo legirnih elementov in elementov v sledovih v talini tehnološko ni mogoče spreminjati s kemijskimi postopki rafinacije, je, brž ko njihova koncentracija preseže dovoljeno mejo, edina rešitev redčenje z dodatkom primarnega aluminija. Tovrstnemu dragemu načinu zagotavljanja predpisane kemijske sestave taline se lahko izognemo le z doseganjem želene kemijske sestave pred taljenjem, tj. na stopnji načrtovanja vhodne zmesi. Preostale nečistoče, kot so npr. vodik in alkalijske kovine ter nekateri vključki (predvsem primarni), lahko uspešno obvladujemo že s sedanjimi postopki rafinacije taline, ki jih tu opisujemo. V tem delu tudi opisujemo (i) sodobne tehnološke postopke načrtovanja recikliranju prijaznih sestav gnetnih aluminijevih zlitin s povečanim deležem odpadnega aluminija, spremljanja koncentracije organskih nečistoč v vhodnem odpadnem aluminiju ter določanja kakovosti taline, pridobljene z različnimi postopki taljenja in rafinacije, in ugotavljamo (ii) ekonomske prednosti proizvodnje gnetnih aluminijevih zlitin z recikliranjem metalurško čistega odpadnega aluminija nižjega cenovnega razreda. Izhajajoč iz sestave in cen različnih vrst odpadnega aluminija ter stroškov njihovega recikliranja nam je uspelo razviti funkcionalni model, ki določa ekonomičnost proizvodnje ingotov iz recikliranega aluminija na osnovi vsebnosti aluminija in legirnih elementov v vhodnem materialu. Model smo aplicirali na različne vrste nizkocenovnega odpadnega aluminija in pokazali, da proizvodnja gnetnih zlitin standardne kakovosti iz tovrstnih virov zagotavlja najvišjo mogočo dodano vrednost