Sinteza in karakterizacija selektivno lasersko pretaljene zlitine AlSi10Mg : magistrsko delo

Velikajne, Nejc (author), Bizjak, Milan (mentor), Paulin, Irena (comentor)

Dodajalne (aditivne) tehnologije oz. 3D tisk je proces izdelave, ki temelji na dodajanju materiala sloj za slojem in predstavlja nov način izdelave strojnih oz. konstrukcijskih elementov. Njeni začetki segajo v 60. leta prejšnega stoletja, danes pa je že tako razširjena, da nas spremlja skoraj na vsakem koraku. Tako jo srečujemo v arhitekturi za tisk maket stavb in naselij, v strojništvu za tisk industrijskih delov, v medicini za tisk implatantov itd. Seznam je neskončen. Glavna prednost tehnologije je enostavna in velika hitrost prototipiranja zahtevnih geometrij, relativno nizka cena za izdelavo majhnih serij in majhna količina odpadnega materiala. Obstajajo različne metode dodajalne proizvodnje. Najpogostejši so procesi posteljne tehnologije pri katerih je dodajni material v obliki prahov in se ta sintra/tali (SLM-selective laser melting, SLS-selective laser sintering, DMLS-direct metal laser sintering, SHS-selective heat sintering). Čeprav tehnologija obeta ogromno, je na področju mehanskih, fizikalnih in kemijskih lastnosti materialov in izdelkov izdelanih po tem postopku še vedno veliko izzivov. V sklopu magistrske naloge je bil uporabljen postopek selektivnega laserskega taljenja (SLM) zlitine AlSiMg10. Pri navedeni tehnologiji, kot že ime pove, selektivno talimo sloje kovinskega prahu. Energijo za taljenje dovedemo s pomočjo laserja. Parametri procesa imajo ključen vpliv na mikrostrukturo in mehanske lastnosti končnega izdelka. Na ta način lahko z razumevanjem osnovnih parametrov vplivamo na končne mehanske lastnosti. Po pregledu literature je bilo ugotovljeno, da materiali z veliko reflektivnostjo in odlično toplotno prevodnostjo predstavljajo velik izziv na omenjenem področju. Velik delež poroznosti, razpoke ter mikrostrukturna nehomogenost so glavne napake izdelkov izdelanih po SLM postopku. Z izbiro ustreznih procesnih parametrov pa jih je možno zmanjšati, v nekaterih primerih celo odpraviti. Tako je bil glavni cilj eksperimentalnih raziskav pridobiti optimalne procesne parametre, katerih razultat je izdelek z čim manj napakami in najvišjimi mehanskimi lastnostmi. Začeli smo z izdelavo procesne mape, kjer smo spreminjali moč laserja ter hitrost vrstičenja. Sledila je priprava metalografskih obrusov in analiza poroznosti s svetlobnim mikroskopom. Pregledali smo mikrostrukturo vzorcev ter izračun deleža poroznosti. Glede na analizo poroznosti smo izdelali procesno mapo. Na ta način smo izbrali tri različne kombinacije parametrov, pri katerih je bil delež poroznosti najmanjši. Izbrano procesno okno smo uporabili pri izdelavi vzorcev za mehanske preizkuse.

• Language: Slovenian
• Keywords: selektivno lasersko pretaljevanje, 3D tisk, zlitina AlSi10Mg, karakterizacija, poroznost, mikrostruktura, mehanske lastnosti.
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: [N. Velikajne]
• Year: 2021
• Number of pages: XVI, 69 f.
• PID: 20.500.12556/RUL-130377
• UDC: 669
• COBISS.SI-ID: 83683331
• Publication date in RUL: 14.09.2021

VELIKAJNE, Nejc, 2021, Sinteza in karakterizacija selektivno lasersko pretaljene zlitine AlSi10Mg : magistrsko delo [online]. Master’s thesis. Ljubljana : N. Velikajne. [Accessed 15 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=130377

Secondary language

• Language: English
• Title: Synthesis and characterization of selective laser melted AlSi10Mg alloy : master's thesis

Abstract

Additive manufacturing or 3D printing is a process of making three dimensional solid objects from a digital file. The creation of a 3D printed object is achieved using additive processes. In an additive process an object is created by laying down successive layers of material until the object is created. Each of these layers can be seen as a thin sliced cross-section of the object. Process is the opposite of subtractive manufacturing which is cutting out / hollowing out a piece of metal with for instance a milling machine. It represents a new way of manufacturing mechanical and constructional elements. The origins go back to the 1960, but nowadays we see it almost everywhere. It can be seen in architecture, used for printing buildings and models, in engineering for manufacturing industrial parts, in medicine for implants, etc. The main advantage of the mentioned technology is simple and fast prototyping of demanding geometry, relatively low price for producing small series, and a small amount of waste material. There are several methods of additive technologies known. Even though mentioned technology can be powerful, there are still some challenges in the field of mechanical, physical, and chemical material properties. In the master's degree thesis, we have used the technology of selective laser melting (SLM) of the AlSiMg10 alloy. As the name of technology tells us, we are selectively melting the layers of the metal powder. The energy for melting is obtained by the laser. The process parameters have a crucial influence on the microstructure and mechanical properties of the final product. With understanding the basic parameters, we can affect the final mechanical properties. After reviewing the literature, we have found out that the materials with large reflectivity and high thermal conductivity represent an enormous challenge for the mentioned technology. A large part of porosity, cracks, and microstructure non-homogeneity are the main flaws of the products made with the SLM technology. By setting the right process parameters we can ease or even prevent them. The main goal of the experimental research was to find most optimal process parameters for producing a batch of samples with the flawless microstrukture and the best mechanical properties. Experimental work started with the manufacture of 12 samples, where we have been changing the laser power and the velocity of the scanning speed. Next, we have prepared metallographic samples for the porosity analysis with a light microscope. We have analized microstructure of the samples and calculated the rate of porosity. This way we have chosen three different combinations of the process parameters where the rate of the porosity was at the lowest. We have used the chosen process window for the manufacture of the samples for further mechanical research.

• Keywords: selective laser melting, 3D printing, AlSi10Mg, characterization, porosity microstructure, mechanical properties.