Karakterizacija mikrostrukture i faznih transformacija Cu-Al-Mn-Ag legura

master's thesis

• Title (english): Microstructure characterization and phase transformations of Cu-Al-Mn-Ag alloys
• Author: Željka Krtić
• Mentor: Tamara Holjevac Grgurić (mentor)
• Committee member: Stjepan Kožuh (predsjednik povjerenstva)
• Committee member: Tamara Holjevac Grgurić (član povjerenstva)
• Committee member: Ljerka Slokar Benić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Metallurgy; Sisak
• Defense date and country: 2020-10-30, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Metallurgy

Abstract

Cu-Al-Mn legure s prisjetljivosti oblika postale su vrlo atraktivne za komercijalnu primjenu u bioinženjerstvu, dentalnoj industriji te u proizvodnji senzora i aktuatora, i sve više zamjenjuju uporabu vrlo skupe Ni-Ti legure, s obzirom na njihovu nisku cijenu koštanja, veliku superelastičnost te izrazitu duktilnost. Efekt prisljetljivosti oblika u istraživanim legurama posljedica je bezdifuzijske martenzitne transformacije, koja podrazumjeva promjenu kristalne strukture materijala. Dodavanjem mangana osnovnoj binarnoj Cu-Al leguri, proširuje se područje -faze, ključnoj fazi za postizanje martenzitne strukture, `-faze, čime se povećava duktilnost materijala te sposobnost njenog hladnog deformiranja. Daljnjim dodavanjem mikrolegirajućih elemenata ternarnoj Cu-Al-Mn leguri, može se utjecati na smanjenje veličine zrna, čvrstoću materijala, pomak faznih transformacija te efekt prisjetljivosti oblika.
Stoga je u ovom radu istražen utjecaj srebra na mikrostrukturu i temperature faznih transformacija Cu-Al-Mn legura. Cu-Al-Mn-Ag legure pripremljene su taljenjem u elektrolučnoj peći te lijevane u cilindrični kalup, dimenzija 8 mm x*1,2 cm. Termodinamički proračun i mehanizam skrućivanja Cu-Al-Mn legura proveden je programom Thermo-Calc, korištenjem termodinamičkih podataka prema Miettinenu. Simultanom tehnikom toplinske analize, diferencijalnom pretražnom kalorimetrijom/termogravimetrijom (STA DSC/TG) određene su temperature transformacija Cu-Al-Mn-Ag legura, dinamičkim mjerenjima kroz 2 ciklusa zagrijavanje/hlađenje, u atmosferi argona. Mikrostrukturna ispitivanja provedena su optičkom mikroskopijom (OM) te skenirajućom elektronskom mikroskopijom (SEM), dok je energijsko disperzijskom spektrometrijom (EDS) određen kemijski sastav istraživanih sustava. Rezultati mikrostrukture korelirani su sa promjenom sastava Cu-Al-Mn-Ag legure i udjelom srebra te pomakom temperatura transformacija.

Abstract (english)

Cu-Al-Mn shape memory alloys became very attractive for commercial use in the bioengineering, dental industry and in the high-demand industry for sensors or actuators, and they are frequently used instead of very expensive Ni-Ti alloy, due to their low cost, superelasticity and high ductility. Shape memory effect is a consequence of the diffusionless martensitic transformation, which implies a change of crystal structure. Addition of manganese to binary Cu-Al alloy, broadens -phase region, parent phase for formation of martensitic structure, `-phase, what increase ductility and cold workability of material. Further addition of alloying elements influences to decreasing of grain size, changes of phase transformation temperatures, mechanical properties and shape memory effect.
In this paper, the effect of silver addition on the microstructure and transformation temperatures of Cu-Al-Mn alloys was investigated. Cu-Al-Mn-Ag alloys were prepared by melting in the electric-arc furnace and casted in the moulds dimensions 8 mm*1.2 cm. Thermodynamic calculation and solidification mechanism was performed by software Thermo-Calc 5, with thermodynamic data according to Miettinen. Transformation temperatures of Cu-Al-Mn-Ag alloys were carried out by simultaneous thermal analysis differential scanning calorimetry/thermogravimetry (STA DSC/TG) through two dynamic cycles in the argon atmosphere. Microstructural investigations were performed by optical microscopy (OM) and scanning electron microscopy (SEM), while chemical content of specimens was determined by energy-dispersive spectrometry (EDS). Microstructural results were correlated with silver content in Cu-Al-Mn-Ag alloy as well as transformation temperatures.

• Keywords: legure s prisjetljivošću oblika; Cu-Al-Mn-Ag; fazne transformacije; martenzit; DSC analiza
• Keywords (english): shape memory alloys; Cu-Al-Mn-Ag; phase transformations; martensitic structure; DSC analysis
• Language: croatian
• URN:NBN: urn:nbn:hr:115:336597
• Study programme: Title: Graduate study program Metallurgy; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka metalurgije (magistar/magistra inženjer/inženjerka metalurgije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2020-11-02 08:55:21