diplomsko delo
Domen Korbar (Author), Milan Bizjak (Mentor)

Abstract

Zlitina CuAlNi spada med t. i. zlitine s spominom oblike. Zanje je značilno, da se lahko s povišanjem temperature povrnejo v prvotno obliko po plastični deformaciji, saj so si sposobne zapomniti obliko, ki so jo imele pred deformacijo. Lastnost oblikovnega spomina omogoča kristalografsko reverzibilna martenzitna transformacija med martenzitom (nizkotemperaturna faza) in avstenitom (visokotemperaturna faza), ki jo spremljajo štiri karakteristične temperature faznih transformacij. Pri segrevanju imamo tako temperaturi začetka in konca avstenitne transformacije (As, Af), medtem ko imamo pri ohlajanju temperaturi začetka in konca martenzitne transformacije (Ms, Mf). Zlitina CuAlNi je še posebej zanimiva med zlitinami s spominom oblike ne samo zaradi nizke cene izdelave, ampak tudi zato, ker je ena izmed edinih visokotemperaturnih zlitin s spominom oblike, ki omogoča aplikacije tudi pri povišanih temperaturah (do 200 °C). Toda njena praktična uporaba je omejena zaradi težke obdelave, nagnjenosti h kristalnemu lomu in nizke toplotne stabilnost. V diplomskem delu smo raziskali vpliv staranja na mikrostrukturo in karakteristične temperature fazne transformacije zlitine CuAlNi. Vzorce smo izdelali v obliki tankih trakov po postopku hitrega strjevanja na prosto vrtečem se valju. Spremembe karakterističnih temperatur faznih transformacij smo spremljali s pomočjo in-situ meritve spremembe električne upornosti po štiritočkovni U-I metodi. Mikrostrukturo vzorcev pred in po staranju na različnih temperaturah smo opazovali s svetlobnim in vrstičnim elektronski mikroskopom. Prav tako pa smo izvedli tudi EDS in XRD analizo.

Keywords

CuAlNi;zlitine s spominom oblike;reverzibilna martenzitna transformacija;karakteristične temperature;staranje;

Data

Language: Slovenian
Year of publishing:
Typology: 2.11 - Undergraduate Thesis
Organization: UL NTF - Faculty of Natural Sciences and Engineering
Publisher: [D. Korbar]
UDC: 669
COBISS: 131503363 Link will open in a new window
Views: 41
Downloads: 8
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Other data

Secondary language: English
Secondary title: determination of characteristic temperatures of Cu-Al-Ni shape memory alloy by measurement of electrical resistance
Secondary abstract: The CuAlNi alloy belongs to the so-called shape memory alloys. They are characterized by the fact that they return to their original shape after plastic deformation when the temperature is increased, because they remember the shape they had before deformation. The shape memory effect is made possible by the crystallographically reversible martensitic transformation between martensite (low-temperature phase) and austenite (high-temperature phase), which is associated with four characteristic phase transformation temperatures: on heating, there are the austenite initial (As) and austenite final (Af) temperatures, and on cooling, there are the martensite initial (Ms) and martensite final (Mf) temperatures. The CuAlNi alloy is particularly interesting among shape memory alloys, not only because of its low manufacturing cost, but also because it is the only high-temperature shape memory alloy that allows applications at higher temperatures (up to 200 °C). However, its practical application is limited due to its difficult processing, its tendency to fracture and its low thermal stability. In the bachelor's thesis, the influence of aging on the microstructure and characteristic temperatures of phase transformations of CuAlNi alloys was studied. The samples were prepared in the form of thin ribbons by the free-jet melt spinning method. The changes in the characteristic temperatures of the phase transformations were monitored by in situ measurements of the changes in electrical resistivity using the four-point U-I method. The microstructure of the samples before and after aging at different temperatures was observed by optical and scanning electron microscopes. We also performed EDS and XRD analyzes.
Secondary keywords: CuAlNi;shape memory alloys;reversible martensitic transformation;characteristic temperatures;aging;
Type (COBISS): Bachelor thesis/paper
Study programme: 0
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Naravoslovnotehniška fak., Oddelek za materiale in metalurgijo
Pages: XII, 41 f.
ID: 16587678