Repository of Faculty of Metallurgy University of Zagreb
Not a member yet
491 research outputs found
Sort by
The influence of copper content on corrosion behavior of ductile iron and austempered ductile iron
Get PDFoai:repozitorij.simet.unizg.hr:simet_232The effect of copper content on corrosion behavior of ductile iron and austempered ductile iron was investigated in 0.5 mol dm-3 NaCl solution at T = 20°C by open circuit potential measurements, linear and potentiodynamic polarisation methods. Ductile iron specimens used in this paper had: 0.031 wt.% Cu and 0.91 wt.% Cu. Specimens were austenitised at 850°C for 60 min and then austempered at 420°C for 60 min in 50% NaNO3 and 50% KNO3 salt bath. The mechanism of the corrosion attack developed on the material surface was analysed by light microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).The results of the electrochemical investigations indicated that corrosion rate generally decrease with the increase in copper content in alloy. Also, higher corrosion resistance showed austempered ductile iron samples compared to ductile iron samples with the same chemical composition
Zbornik radova 17. MEĐUNARODNO SAVJETOVANJE LJEVAČA: Visokotehnološka rješenja u ljevarstvu i inženjerstvo utemeljeno na znanju
No full textFoundry industry as a base branch represents an important factor contributing to the economic potential of each country. Current market development as well as technical and economic objective, the production of high-quality, low- cost and environmentally friendly casting, requires application of recent and advanced materials, as well as production technologies, followed and supported by understanding of production process. Production imperative is pointed into the recent technologies and improved materials for everyday usage in our homes, workplaces, as well as materials with special requirements for specific applications such as those for the automotive or space industry. Industrial activities, which are defined as strategic activities in the Republic of Croatia are Metal Casting and Production of Final Metal Products, recognized as "economic growth drivers" because they are expected to realize higher rates of growth and employment. Hi-Tech casting solution comprehends to recent technology and educated and skilled engineers. The Conference topics were designed as presentations of the current "state of the art" research in collaboration with industry, and production innovation with the aim to improve the competitiveness. The scope of 17th International Foundrymen Conference (IFC) covers scientific, technological and practical aspects concerning research, development and application of casting technology with the common perspective – increase of competitiveness. Special attention will be focused towards the competitiveness ability of foundries, improvement of materials features and casting technologies, environmental protection as well as subjects connected to the application of castings. During this Conference 44 papers will be presented. Book of Abstracts of the 17th International Foundrymen Conference includes summaries of the papers. The Proceedings book consists of papers in extenso published in electronic format (CD). Full length papers have undergone the international review procedure, done by eminent experts from corresponding fields, but have not undergone linguistic proof reading. Sequence of papers in Proceedings book has been done by category of papers in following order: plenary lectures, invited lectures, oral and poster presentation, and inside the category alphabetically by the first author’s surname. This occasion represents the opportunity to discuss and increase the mutual collaboration between HEIs’ and industry with the aim of information exchange related to advanced experience in foundry processes and technologies, gaining the new experience in presentation and / or teaching process within lifelong learning process
The effect of the processing parameters on the martensitic transformation of Cu-Al-Mn alloys
Get PDFLegure 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.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
Tool steels - classification and basic properties
Get PDFU ovom radu dan je pregled proučavanja metalurških procesa naprednih metalnih materijala. Termodinamičke karakteristike procesa obuhvadaju uvjete prema kojima je mogude pratiti odvijanje procesa u željenom pravcu te kinetiku odvijanja procesa. Alatni čelici pripadaju skupini naprednih metalnih materijala od kojih se zahtijevaju posebna svojstva poput visoke tvrdode i otpornosti na trošenje, postojanost čvrstode kod povišenih temperatura, dobro ponašanje pri toplinskoj obradi, korozijska otpornost i dr. Postizanje dobrih svojstava omogudeno je legiranjem kromom, volframom, vanadijem, molidbenom ili kobaltom. Veoma je bitno u kojoj mjeri se dodaju legirajudi elementi i kako teče proces proizvodnje, jer spojevi koji nastaju tijekom proizvodnje mogu se mijenjati i tako utjecati na transformacijske procese te se izlučiti u nepoželjnom obliku. Legirajudi elementi se najčešde spajaju s ugljikom u karbide, ali također mogu dijelom supstituirati u kristalnu rešetku željeza te stvarati nepoželjne intermetalne spojeve. U svrhu poboljšanja svojstava alatnih čelika, teži se pronalasku adekvatnog kemijskog sastava kako bi se omogudilo dobivanje stabilnih termodinamičkih parametara.This paper presents an overview of metallurgical processes of advanced metallic materials. The thermodynamic characteristics of the process include the conditions under which it is possible to follow the process in the desired direction and kinetics of the process. Tool steels belong to a group of advanced metallic materials, which are required by special properties such as high hardness and wear resistance, high strength stability at elevated temperatures, good behavior during heat treatment, high corrosion resistance etc. Achieving good properties is enabled by alloying with chromium, tungsten, vanadium, molybdenum or cobalt. It is very important to what extent the alloying elements are added and how the process of production proceeds, because the compounds formed during the production can be altered, and thus affect the transformation processes, and secreted in an undesirable form. Alloying elements are most often combined with carbon in carbides but can also be partially substituted in the iron crystal lattice and create undesirable intermetallic compounds. In order to improve the properties of tool steels, the aim is to find an adequate chemical composition to enable obtaining stable thermodynamic parameters
Properties, production and application of compacted graphite iron
No full textVermikularni lijev je vrsta željeznog lijeva u kojem je većina ugljika prisutna u obliku vermikularnih grafitnih čestica. Te čestice nalaze se u metalnoj osnovi koja se uglavnom sastoji od ferita, ferita i perlita ili perlita. Po svojim fizikalnim i mehaničkim svojstvima može se svrstati između sivog i nodularnog lijeva.
Proizvodnja vermikularnog lijeva je znatno teža od proizvodnje sivog i nodularnog lijeva jer brojni procesni parametri utječu na stvaranje vermikularnog grafita tijekom skrućivanja. Već vrlo mala odstupanja od njihovih optimalnih vrijednosti mogu rezultirati stvaranjem listićavog ili nodularnog grafita.
Vermikularni lijev odavno je poznat. Međutim, otežani postupak proizvodnje ograničio je njegovu značajniju primjenu u prošlosti. Proširenje spoznaja o vermikularnom lijevu, napredak ljevačke tehnologije i kontrole procesa proizvodnje omogućili su njegovu širu primjenu. Danas se vermikularni lijev primjenjuje za brojne aplikacije. Najširu primjenu ima u industriji motornih vozila za komponente od kojih se istovremeno zahtijeva otpornost na toplinska opterećenja i čvrstoća.
U ovom preglednom radu prikazane su norme za vermikularni lijev, faktori koji utječu na njegova svojstva, proizvodnja vermikularnog lijeva te njegova svojstva i primjena.Compacted (vermicular) graphite iron is a type of cast iron in which the majority of the carbon is present in the form of compacted graphite particles. These particles are placed in a metal matrix which consists mainly of ferrite, ferrite and pearlite, or pearlite. According to its physical and mechanical properties, compacted graphite iron can be placed between gray and ductile iron.
Production of compacted graphite iron is more complicated than the production of gray and ductile iron because numerous process parameters influencing the formation of compacted graphite during solidification. Already very small deviations from their optimal values may result in the formation of flake or nodular graphite.
Compacted graphite iron has long been known. However, the difficult process of production has limited its significant application in the past. Increase of knowledge about compacted graphite iron, progress of foundry technology and production process control has enabled its wider application. Today, compacted graphite iron is used for numerous applications. It is mainly used in in the motor vehicle industry for components which at the same time must have a resistance to thermal loads and strength.
This review paper shows the standard for compacted graphite iron, the factors that affect its properties, production of compacted graphite iron and its properties and application
The effect of nickel content on properties of Cu-Al-Mn-Ni shape memory alloy
Get PDFU okviru ovog rada provedena je analiza utjecaja različitog sadržaja nikla (2-5 mas.%) na
mikrostrukturu i mikrotvrdoću Cu-Al-Mn-Ni legure s prisjetljivosti oblika. Pomoću peći za
taljenje obavljeno je taljenje i lijevanje ingota u vodom hlađenoj, posebno konstruiranoj
bakrenoj anodi koja je služila i kao kalup za lijevanje. Nakon taljenja uzorci su tri puta
pretaljivani upotrebom električnog luka kako bi se postigla homogenost kemijskog sastava.
Postupkom taljenja i lijevanja proizvedeni su uzorci valjkastog oblika odnosno ingoti
promjera 8 mm i duljine 15 mm. Odabrani uzorci su i toplinski obrađeni (900 °C/15min/H2O)
kako bi se pratio utjecaj toplinske obrade. Uzorci su analizirani u lijevanom i kaljenom stanju.
Mikrostrukturna analiza provedena je pomoću optičke i pretražne elektronske mikroskopije,
energetsko disperzijske spektroskopije i diferencijalno skenirajuće kalorimetrije. Ispitivanje
mikrotvrdoće provedeno je metodom po Vickersu. U svim analiziranim uzorcima utvrđena je
prisutnost β´1 martenzita. Porast sadržaja nikla do 3% utjecao je na smanjenje temperatura
faznih transformacija, dok je daljnjim porastom do 5% nikla uočen ponovni porast
temperatura faznih transformacija. Sličan trend zamijećen je i u vrijednostima mikrotvrdoće.In this work, the effect of various nickel content (2-5 wt.%) on microstructure and
microhardness of Cu-Al-Mn-Ni shape memory alloy was analyzed. The melting furnace was
used to melt and cast the ingots in a water-cooled, specially designed copper anode which also
was used as a casting mould. After melting, the samples were remelted three times using an
electrical arc to achieve homogeneity of the chemical composition. By these procedures,
samples of cylindrical shape, ingots of 8 mm diameter and 15 mm length, were produced.
Selected samples were heat treated (900 °C/15min/H2O) to monitor the influence of heat
treatment. Samples were analyzed in as-cast and as-quenched state. Microstructural analysis
was performed by optical and scanning electron microscopy, energy dispersive spectroscopy
and differential scanning calorimetry. Microhardness testing was carried out by Vickers
method. In all analyzed samples, the presence of β'1 martensite was determined. The increase
of the nickel content up to 3% affected to the reduction of the phase transformations
temperatures, while a further increase of nickel content up to 5%, the phase transformations
temperatures rise again. A similar trend was observed in the values of microhardness
Comparison of photocatalyst preparation by TiO2 deposition on a support using different methods
Get PDFProblematika zaštita voda već dugo je jedna od najvažnijih tema zaštite okoliša. Kada se govori o mikroonečišćenjima u vodi jedan od najvećih problema su farmaceutici. Utvrđivanje njihove prisutnosti nije samo posljedica razvoja analitičkih metoda nego i masovne uporabe farmaceutika te njihove sve veće koncentracije u okolišu. U ovom radu su pripremljeni i karakterizirani napredni fotokatalizaori dobiveni kroz dva različita postupka imobilizacije titanijeva dioksida (TiO2) na nosač sol-gel metodom. Imobilizacija je provedena klasičnim i mikrovalnim sušenjem te su katalizatori karakterizirani pretražnom elektronskom mikroskopijom (SEM), energijsko disperzivnom rendgenskom spektroskopijom (EDS) i rendgenskom difrakcijskom analizom (XRD). Aktivnost
fotokatalizatora je ispitana kroz sposobnost fotokatalitičke razgradnjom salicilne kiseline (SA) u pilot reaktoru, čija je razgradnja praćena UV-ViS spektrometrom.The issue of water protection has long been one of the most important environmental issues. When it comes to the micropollutants, one of the greatest problems is pharmaceuticals. Their detection is not only a consequence of the development of analytical methods but also of the massive use of pharmaceuticals and their increasing concentration in the environment. In this paper, advanced photocatalysts were prepared and characterized by two different processes of titanium dioxide immobilization (TiO2) on the support through sol-gel method. Immobilization was performed by the classical and microwave-assisted drying, and the catalysts were characterized by scanning electron microscopy (SEM), energy dispersion X-ray spectrometry (EDS) and X-ray diffraction analysis (XRD). The photocatalyst activity was tested through the photocatalytic degradation of salicylic acid (SA) in the pilot reactor, monitoring the degradation by the UV-vis spectrometry
Otuđenje rada iz Marxove i kršćanske perspektive
Get PDFRad je ljudsko pravo, a plodovi rada logičnopripadaju izvršitelju rada, radniku. Otuđenje rada negacija je ljudskog dostojanstva i etički je potpuno neprihvatljivo svakoj osobi ili instituciji koja vjeruje u jednakost i ravnopravnost svih ljudskih bića. Otuđenje rada je nepravda iz marksističke perspektive, a grijeh iz kršćanske perspektive. Ukoliko neki pojedinac ili grupa smatra da pojedini ljudi mogu dominirati nad slobodnom voljom drugih i iskorištavati ih za svoje potrebe, tada se takva osoba ili institucijanema pravo nazivati kršćanskom, a jednako tako niti marksističkom.Dokidanje otuđenja rada preduvjet je uspostave pravednog i slobodnog društva. Uspostava društva u kojem će svi ljudi moći, bez obzira na nacionalnost, vjeroispovijest, rasu, spol, rod, spolnu usmjerenost, dob, zdravstveno stanje ili koju drugu odrednicu identiteta, u skladu sa svojim talentima, intelektualnim i fizičkim potencijalima, slobodno i sretno živjeti zajednički je cilj marksista i kršćana. I to nije utopijski cilj
Corrosion Protection of Copper in Sodium Chloride Solution using Propolis
Get PDFIn this investigation the possibility of inhibiting corrosion of copper using ethanol extract of propolis in 0.5 mol dm-3 NaCl solution was investigated. The measurements were carried out in 200 cm3 of NaCl solution to which 4 ml of ethanol extract of propolis was added. Also, the protective effect of propolis coating, which was formed by applying the ethanol extract of propolis to the electrode surface, followed by air drying for 24 h, was investigated. Experiments were performed using electrochemical methods: open circuit potential measurements, linear and potentiodynamic polarization method and electrochemical impedance spectroscopy measurements (EIS). The results showed that the coating of propolis significantly shifted the value of the open circuit potential of Cu to more positive values, significantly increased the value of polarization resistance and as well led to a reduction in corrosion current density. On the other hand, addition of propolis in solution yielded minor changes in the value of the stable open circuit potential of copper, but increased the value of polarisation resistance and decreased the corrosion current density. After polarisation measurements, the electrode surface was examined by optical microscopy. Quantum chemical modelling of selected constituents of propolis was undertaken in order to ascertain their contributions to the corrosion inhibition performance
Influence of Cu on the microstructure development of AlSi7MgCu alloy
No full textDesigning and characterisation of AlSi7MgCu alloy with extra addition of Cu (up to 1.435 wt.%) represents a challenge in order to achieve advanced mechanical properties already in as-cast state. Microstructural investigation of AlSi7MgCu alloy reveals a wide range of complex reactions and possible intermetallic phases due to the interaction of alloying and trace elements. An extra addition of Cu (up to 1,435 wt.%) as a secondary alloying element initiates an additional interaction with transition elements Fe, Mn and secondary alloying element Mg. Evolution of microstructure and determination of solidification sequence enables detail overview of solidification path in both states, as-cast and heat-treated. Enrichment of solidification process with complex intermetallic phases reveals following constituents: dendrite network; iron-based needle-like Al5SiFe and / or complex Chinese script formation Al15(Fe,Mn,Cu)3Si2; main eutectic (αAl+βSi); complex eutectic clusters of Al8Mg3(Fe,Mn,Cu)Si6 and Al5(Fe,Mn,Cu)2Mg8Si6 phase and secondary eutectic phase precipitations αAl+Mg2Si and αAl+Al2(Fe,Mn,Cu). Infiltration of common transition elements such as Fe and Mn in Cu bearing phases’ resulted in high total content of transition elements (Fe+Mn+Cu). Microstructural investigation also indicates continuous interaction of Fe, Mn and Cu in formation of wide range of intermetallic phases´ through the whole solidification process. The nature (morphology and alloying elements interaction) of formed intermetallic phases comprehends to the tensile mechanical properties development due to strong connections and interactions during solidification process as a whole