Fazne pretvorbe

master's thesis

• Title (english): PHASE TRANSITIONS
• Author: Ivana Kušec
• Mentor: Željko Skoko (mentor)
• Committee member: Željko Skoko (predsjednik povjerenstva)
• Committee member: Gorjana Jerbić-Zorc (član povjerenstva)
• Committee member: Vito Despoja (član povjerenstva)
• Committee member: Damir Pajić (član povjerenstva)
• Committee member: Maro Cvitan (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2015-03-13, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Istraživanje faza, faznih pretvorbi te pripadajućih faznih dijagrama atraktivna je tema istraživanja u području materijala. Dobiveni rezultati, najčešće metodom rentgenske difrakcije, otkrivaju npr. kristalnu strukturu, deformacije, brzinu rasta nove faze, ovisnost o molnom udjelu komponenti, ovisnost o temperaturi. U ovom diplomskom radu prikazana su osnovna načela termodinamike za lakše praćenje i razumijevanje faznih dijagrama. Razmotreni su slučajevi jednokomponentnih te dvokomponentnih faza gdje je iznesen detaljan opis istih u smislu uvjeta ravnoteže te ponašanja pojedinih komponenata u sustavu. Nadalje, u radu je detaljno prikazan primjer kada su tri faze u ravnoteži što uzrokuje invarijantne reakcije. Temeljno polazište svakog navedenog primjera jest razmatranje slobodne energije, entalpije, entropije i kemijskog potencijala. U nastavku rada prikazane su difuzijske fazne pretvorbe uz koje su dana klasična i parabolična rješenja. Izneseno je također objašnjenje fenomena precipitacije. Završni dio rada predstavlja eksperimentalni dio koji proučava fazne pretvorbe u slitinama aluminij-cink. Mikrostruktura navedene istraživana je primjenom rentgenske difrakcije, transmisijske elektronske mikroskopije i termičkih metoda. Temperaturna ovisnost mikrostruktura razmatrana je za slučajeve brzo kaljenih-starenih i sporo hlađenih slitina. Na samom kraju sažeti su rezultati u poglavlju Zaključak.

Abstract (english)

Investigation of phases, phase tranfsormations and corresponding phase diagrams is a very attractive subject in the field of material science. Results obtained, most often, by X-ray diffraction reveal crystal structure, stress and strain, growth rate of new phases, component molar dependence, and temperature dependence. At the beginning of this Diploma thesis basis of thermodynamics are given which should help with the understanding of the phase diagrams. Single component and binary phase diagrams are studied, and a detailed explanation of equilibrium and behaviour of phases in the system is given. Further on, an example of a three component equilibrium system is given with invariant reactions. Basis of all the examples is a determination of free energy, enthalpy, enrtropy and chemical potential. This is being followed by diffusive phase transitions, for which classical and parabolic solutions are calculated. Also, the precipitation phenomenon is explained.
Final part is experimental, investigation phase transitions in the Al-Zn alloy. Microstructure of the given alloy was investigated by the means of X-ray powder diffraction, transmission electron microscopy and thermal methods. Temperature dependence of the microstructure was explored for slowly-cooled and water-quenched alloys. Finally, the results are adjourned in the summery.

• Keywords: termodinamika; fazni dijagrami; difuzija; Zenerova aproksimacija; Hillertova aproksimacija
• Keywords (english): thermodynamics; phase transitions; diffusion; Zener approximation; Hillert approximation
• Language: croatian
• URN:NBN: urn:nbn:hr:217:877133
• Study programme: Title: Physics and Technology; specializations in: Education; Course: Education; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra edukacije fizike i tehnike (magistar/magistra edukacije fizike i tehnike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-04-04 20:28:07