Modelling and optimization of aluminum waste recycling process in solid state

Abstract

Tema ove disertacije je istraživanje procesa recikliranja aluminijskog otpada u čvrstom agregatnom stanju. Taj pristup u ekonomskom i ekološkom smislu je povoljniji od konvencionalnog recikliranja zbog manjeg utroška energije, ispuštanja stakleničkih plinova u atmosferu i većeg stupnja iskorištenja materijala. U ovoj disertaciji, pisanoj prema Skandinavskom modelu, može se dobiti cjelovita slika o proizvodnji kvalitetnih uzoraka recikliranih bez pretaljivanja metala. U većem dijelu istraživanja korištena je metodologija planiranja pokusa s ciljem dobivanja matematičkih modela koji služe kao značajan, postojan i nepristran alat u opisivanju inovativnog procesa. U prvom istraživanju proučavano je recikliranje procesom istosmjernog istiskivanja u toplom stanju te je zaključeno da je temperatura istiskivanja najutjecajniji parametar na kvalitetu recikliranih uzoraka. U sljedeća dva istraživanja, u kombinaciji s istiskivanjem, korišten je proces intenzivne plastične deformacije što je dovelo do značajnog poboljšanja kvalitete recikliranih uzoraka. U četvrtom istraživanju proučavan je utjecaj toplinske obrade u kombinaciji s procesom intenzivne plastične deformacije. Time su dobiveni kvalitetni reciklirani uzorci što su pokazala ispitivanja mehaničkih i fizikalnih svojstava, kao i metalografska analiza. U finalnom istraživanju, pokazano je da su korozijska svojstva uzoraka recikliranih u čvrstom stanju bolja, dok je životni vijek pod dinamičkim opterećenjem sličan u odnosu na konvencionalno proizvedene uzorke.The topic of this dissertation is to investigate the process of recycling aluminium waste in solid state. That approach in both economic and environmental terms is more appropriate than conventional recycling process due to the reduced energy consumption, greenhouse gasses emissions and higher material yield. In this doctoral dissertation, written according to the Scandinavian model, can be given a complete picture of the production of quality samples recycled without metal remelting. In most part of the research it was used design of experiments methodology with aim to derive mathematical models which should serve as a significant, robust and impartial tool in describing an innovative process. In first research solid state recycling using hot direct extrusion was investigated with conclusion that extrusion temperature was most influence parameter on recycled samples quality. In next two researches in combination with direct hot extrusion, severe plastic deformation process was used leading to significant increase of the recycled samples quality. In fourth research, influence of the heat treatment in combination with severe plastic deformation process was investigated thus producing quality recycled samples which was confirmed with mechanical and physical properties determination as well as metallographic analysis. In the final research, it was showed that corrosion properties of the samples recycled in solid state are better, while fatigue life was similar to that of conventionally produced samples