Title Utjecaj procesnih parametara na martenzitnu transformaciju Cu-Al-Mn legure Title (english) The effect of the processing parameters on the martensitic transformation of Cu-Al-Mn alloys Author Željka Krtić Mentor Tamara Holjevac Grgurić (mentor)Committee member Mirko Gojić (predsjednik povjerenstva)Committee member Tamara Holjevac Grgurić (član povjerenstva)Committee member Stjepan Kožuh (član povjerenstva)Granter University of Zagreb Defense date and country 2018-09-17, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Legure s prisjetljivošću oblika (SMA) karakteriziraju dva jedinstvena efekta,
pseudoelastičnost i efekt prisjetljivosti oblika, koji je posljedica bezdifuzijske austenitnomartenzitne transformacije u strukturi materijala. Cu-Al-Mn legure s prisjetljivošću oblika
vrlo su atraktivne za komercijalnu primjenu, s obzirom na njihovu nisku cijenu koštanja,
veliku superelastičnost, izvrsnu duktilnost te dobru obradivost hladnim deformiranjem.
U ovom radu, istražen je utjecaj procesnih parametara i uvjeta toplinske obrade na promjenu
mikrostrukture i temperature martenzitne transformacije Cu-Al-Mn legura. Cu-8 % mas. Al-9
% mas. Mn legure s prisjetljvošću oblika pripremljene su taljenjem u elektrolučnoj peći te
kontinuiranim lijevanjem. Istraživane legure zatim su toplinski obrađene pri temperaturi od
900 °C kroz 30 minuta te naglo hlađene u vodi. Termodinamički proračun stabilnosti faza
ternarnog Cu-Al-Mn sustava u ravnotežnim uvjetima, proveden je programom Thermo-Calc
5. Ispitivanje mikrostrukture Cu-Al-Mn legura, u lijevanom stanju i nakon toplinske obrade
materijala, provedeno je pretražnim elektronskim mikroskopom opremljenim energijsko
disperzijskim spektrometrom (SEM-EDS). Diferencijalnom pretražnom kalorimetrijom
(DSC) utvrđene su temperature početka i završetka austenitne i martenzitne transformacije,
kao i odgovarajuće entalpije. Dobiveni rezultati istraživanja pokazali su djelomično
formiranje martenzitne strukture u lijevanom stanju Cu-Al-Mn legure, dobivene
kontinuiranim lijevanjem te potpuno formiranje martenzitne strukture, uglavnom V-tipa,
nakon toplinske obrade i kaljenja materijala. Cu-Al-Mn legura pripremljena u elektrolučnoj
peći, u lijevanom stanju pokazala je dvofaznu, α + β strukturu, i tek nakon toplinske obrade
materijala početak formiranja martenzitne faze, uz dominantnu α -fazu u strukturi legure.
DSC rezultati pokazali su početak martenzitne transformacije kontinuirano lijevane Cu-Al-Mn legure pri temperaturi 36 °C, odnosno nakon kaljenja pri temperaturi 43 °C.
Abstract (english) Shape memory alloys (SMA) exhibit unique properties such as a pseudoelasticity and shape
memory effect that is a consequence of difussionless austenitic-martensitic transformation.
Cu-Al-Mn alloys are commercially very attractive materials due to low cost, superelasticity,
excellent ductility and cold workability.
In this work, the influence of processing parameters as well as heat-treatment on the
microstructure and martensitic transformations temperatures of Cu-Al-Mn shape memory
alloy was investigated. Cu-8 % wt. Al-9 % wt. Mn SMA alloy was prepared by melting in the
electric-arc furnace and by continuous casting. Alloys were heat-treated at 900 °C for 300
minutes and then quenched in the water. Thermodynamic modelling of stable phases for
ternary Cu-Al-Mn system in the equilibrium conditions was performed by Thermo-Calc 5
software. Microstructure investigations of Cu-Al-Mn alloy, in the as-cast state and after heattreatment, were carried out by scanning electron microscope equipped by energy dispersive
spectrometer (SEM-EDS). Differential Scanning Calorimetry (DSC) was performed for
determination of starting and finishing austenitic and martensitic transformation temperatures
as well as enthalpies. Results showed partially formation of martensitic structure in the as-cast
state of the continuously cast Cu-Al-Mn alloy, and completely martensitic phase, mostly Vshape martensite, after heat-treatment. Cu-Al-Mn SMA alloy prepared by electric-arc melting
in the as-cast state showed two-phase morphology, α + β, and after heat-treatment inception
of martensite phase, with predominant α-phase. DSC results indicated start martensitic
transformation temperature at 36 °C for as-cast and 43 °C for heat-treated continuously cast
SMA alloy.
Keywords
legure s prisjetljivošću oblika
Cu-legure
martenzitna transformacija
mikrostruktura
Keywords (english)
shape memory alloys
Cu-based alloys
martensitic transformation
microstructure
Language croatian URN:NBN urn:nbn:hr:115:691192 Project Number: IP-2014-09-3405 Study programme Title: Metallurgy; specializations in: Metallurgical Engineering, Industrial Ecology Type of resource Text File origin Born digital Access conditions Open access Terms of use Public note Ovaj je rad financirala Hrvatska zaklada za znanost projektom IP-2014-09-3405. Created on 2018-09-07 08:36:12
