Additive manufacturing, more generally 3D printing, have seen remarkable advancements, establishing these technologies as critical tools in modern engineering and manufacturing. 3D printing is a technique that uses three-dimensional data modelling to create a wide range of complex patterns. Thixo-printing is a specialised form of 3D printing that implies the thixotropic extrusion of semi-solid metal alloys. The material can flow while it is under stress since it exhibits both liquid and solid qualities, however it retains enough structure to maintain its shape. Among the materials used in these processes, aluminium, has gained interest due to its favoured properties. This thesis is focused on optimizing a Semi-Solid Extrusion (SSE) 3D printing process for an Al-Si alloys, using a setup which was designed and assembled in previous works. In particular, the main goal was to determine the optimal printing temperature to achieve the desirable globular microstructure necessary for effectively printing at the semi-solid state. The initial phase of the study involved the calibration of the printing setup, with a focus on determining the suitable positioning of essential components, such as the nozzle tip and induction coil, and assessing the temperature distribution within the nozzle. This step was critical in ensuring that the extrusion process could be precisely controlled to achieve the desired material properties and globular microstructure. Subsequent phases of the research involved performing semi-solid printing tests at different temperatures (590°C, 593°C, 596°C, 599°C, 603°C, 605°C, and 610°C), to identify the appropriate temperature for printing process. The microstructure of the extruded samples was analysed using optical microscopy to assess the effect of temperature on the formation of globular structures within the Al-Si alloy. Finally, printing tests were performed at 600°C using two different build plates (aluminium and quartz) to evaluate the practical implications of the optimized temperature on the printing process and possibility of the printing a layer. The results indicated that 600°C was proper for achieving a globular microstructure; however, challenges related to adhesion between the printed material and the substrate were observed. These findings underscore the importance of further refining the printing parameters and control protocols to enhance the quality and reliability of SSE 3D printing for Al-Si alloys.
La manifattura additiva e la stampa 3D sono notevolmente progredite, consolidando queste tecnologie come strumenti fondamentali nell'ingegneria e nella produzione moderna. La stampa 3D è una tecnica che utilizza la modellazione tridimensionale per creare una vasta gamma di schemi complessi. La stampa tixotropica è una forma specializzata di stampa 3D che implica l'estrusione tixotropica di leghe metalliche allo stato semi-solido. Il materiale sottoposto a stress può fluire, poiché presenta sia caratteristiche liquide che solide, ma conserva una struttura sufficiente per mantenere la propria forma. Tra i materiali utilizzati in questi processi, l'alluminio ha guadagnato interesse grazie alle sue proprietà favorevoli. Questa tesi è focalizzata sull'ottimizzazione di un processo di stampa 3D ad estrusione semi-solida per una lega Al-Si, utilizzando un setup progettato e assemblato in studi precedenti. L'obiettivo principale della tesi è determinare la temperatura di stampa ottimale per ottenere la microstruttura globulare necessaria per una stampa efficace allo stato semi-solido. La fase iniziale dello studio ha comportato l’ottimizzazione del setup di stampa, con un focus sull’adeguato posizionamento dei componenti essenziali, come la testa di stampa e la bobina di induzione, e sulla valutazione della distribuzione della temperatura all'interno dell'testa di stampa. Questo passo è cruciale per garantire il controllo del processo di estrusione e per l’ottenimento della microstruttura globulare desiderata. Le fasi successive della ricerca hanno riguardato l'esecuzione di test di stampa semi-solida a differenti temperature (590°C, 593°C, 596°C, 599°C, 603°C, 605°C e 610°C), per identificare la temperatura più appropriata per il processo di stampa. La microstruttura dei campioni estrusi è stata analizzata utilizzando la microscopia ottica per valutare l'effetto della temperatura sulla formazione di strutture globulari all'interno della lega Al-Si. Infine, sono stati eseguiti test di stampa a 600°C utilizzando due diverse piastre di costruzione (alluminio e quarzo) per valutare le implicazioni pratiche della temperatura ottimizzata sul processo di stampa e sulla possibilità di stampare uno strato. I risultati hanno indicato che 600°C era la temperatura adeguata per ottenere una microstruttura globulare; tuttavia, sono stati osservati problemi relativi all'adesione tra il materiale stampato e il substrato. Questi risultati sottolineano l'importanza di ulteriori affinamenti dei parametri di stampa e dei protocolli di controllo per migliorare la qualità e l'affidabilità della stampa tixotropica per le leghe Al-Si allo stato semi-solido.
Optimization and Microstructural Control of Thixotropic 3D Printing of Al-Si
Sadeghi, Reyhaneh
2023/2024
Abstract
Additive manufacturing, more generally 3D printing, have seen remarkable advancements, establishing these technologies as critical tools in modern engineering and manufacturing. 3D printing is a technique that uses three-dimensional data modelling to create a wide range of complex patterns. Thixo-printing is a specialised form of 3D printing that implies the thixotropic extrusion of semi-solid metal alloys. The material can flow while it is under stress since it exhibits both liquid and solid qualities, however it retains enough structure to maintain its shape. Among the materials used in these processes, aluminium, has gained interest due to its favoured properties. This thesis is focused on optimizing a Semi-Solid Extrusion (SSE) 3D printing process for an Al-Si alloys, using a setup which was designed and assembled in previous works. In particular, the main goal was to determine the optimal printing temperature to achieve the desirable globular microstructure necessary for effectively printing at the semi-solid state. The initial phase of the study involved the calibration of the printing setup, with a focus on determining the suitable positioning of essential components, such as the nozzle tip and induction coil, and assessing the temperature distribution within the nozzle. This step was critical in ensuring that the extrusion process could be precisely controlled to achieve the desired material properties and globular microstructure. Subsequent phases of the research involved performing semi-solid printing tests at different temperatures (590°C, 593°C, 596°C, 599°C, 603°C, 605°C, and 610°C), to identify the appropriate temperature for printing process. The microstructure of the extruded samples was analysed using optical microscopy to assess the effect of temperature on the formation of globular structures within the Al-Si alloy. Finally, printing tests were performed at 600°C using two different build plates (aluminium and quartz) to evaluate the practical implications of the optimized temperature on the printing process and possibility of the printing a layer. The results indicated that 600°C was proper for achieving a globular microstructure; however, challenges related to adhesion between the printed material and the substrate were observed. These findings underscore the importance of further refining the printing parameters and control protocols to enhance the quality and reliability of SSE 3D printing for Al-Si alloys.| File | Dimensione | Formato | |
|---|---|---|---|
|
R.Sadeghi.pdf
accessibile in internet solo dagli utenti autorizzati
Descrizione: Optimization and microstructural control of thixotropic 3D printing of Al-Si
Dimensione
42.5 MB
Formato
Adobe PDF
|
42.5 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/227277