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The influence of melt processing on microstructure and mechanical properties of AlSi12 alloy
Get PDFMehanička svojstva aluminijskih legura ovisna su o mikrostrukturnim parametrima poput
veličine i oblika zrna, udaljenosti između dendritnih grana, veličini i raspodjeli primarnih i
sekundarnih faza i uključaka. Kontrola tih parametara ostvaruje se obradom taline te
utjecajem na proces skrućivanja i hlađenja. Obrada taline provodi se s ciljem usitnjenja
primarnog zrna aluminija cijepljenjem, odnosno modifikacijom mehanizma rasta eutektika
(α-Al + β-Si).
U ovom je radu ispitana AlSi12 legura za proizvodnju gravitacijski lijevanih zateznih
stezaljki u tvrtki Dalekovod d.o.o. Cilj provedenog istraživanja bio je procijeniti utjecaj
tehnološke obrade taline i debljine stjenke na razvoj mikrostrukture i mehanička svojstva
AlSi12 legure gravitacijski lijevane u pješčani kalup i kokilu. Istraživanje je temeljeno na
hipotezi da se odgovarajućom tehnološkom obradom taline može poboljšati metalurška
kvaliteta taline te na taj način utjecati na razvoj i pojavu grešaka u mikrostrukturi.
Modifikacija taline dodatkom sredstva na bazi natrija, odnosno stroncija, osigurala je
izlučivanje eutektika (α-Al + β-Si) potpuno modificirane morfologije te smanjenje razlike u
mikrostrukturi i mehaničkim svojstvima.Mechanical properties of aluminum alloys depend on microstructural parameters such as
grain size and shape, distance between dendritic arms, size and distribution of primary and
secondary phases and inclusions. These parameters are controlled by melt processing and the
influence on solidification and cooling process. The melt treatment is carried out by refining
of primary aluminum grain by inoculation or by modification of the eutectic (α-Al + β-Si)
growth mechanism.
This paper examines AlSi12 alloy for the production of gravity cast clamps in a company
Dalekovod d. o. o. The aim of this study was to evaluate the influence of technological
processing of melt and wall thickness on the development of microstructure and mechanical
properties of AlSi12 alloy using gravity casting in sand mold and permanent mold. The
research is based on the hypothesis that adequate technological processing of the melt can
improve the metallurgical quality of the melt and thus influence the development and
occurrence of defects in the microstructure. Modification of the melt with the addition of
sodium or strontiumbased agents provided complete modification of eutectic (α-Al + β-Si)
morphology and reduced the difference in microstructure and mechanical properties
Influence of the AlSi12 alloy inoculation on the microstructure and mechanical properties development
No full textDue to a wide range of favourable properties, aluminium alloys found its application in almost all industrial branches. Potential of improving the usage properties has been recognized through forming of favourable intermetallic in mutual interaction of numerous alloying elements such as silicon, copper or magnesium, along with trace elements such as iron and manganese. Other important elements such as titanium, boron, strontium or sodium are intently added through targeted melt treatment in order to improve solidification path by increasing the nucleation potential and therefore changing morphology. Consideration of the casting technology parameters which influence the cooling / solidification rate also represent the base for changing the microstructure and final quality of the casting. Synergy activity of alloying and/or trace elements and theirs interaction and technological parameters of casting process is of great importance in consideration of alloy applicability. This investigation deals with EN AC AlSi12 (EN AC 44100) eutectic alloy with narrow solidification interval, intended for rapid cooling/solidification technology such as high pressure casting (HPDC). Effect of different mode of AlSi12 alloy melt treatment on microstructure and mechanical properties was monitored as a quality insurance. Applied melt treatment mode consists of modification of eutectic with addition of AlSr10 master alloy in all investigated cases. The difference in melt treatment mode was in targeted addition of AlTi5B master alloy. Hypothesis of the examination is based on the assumption that targeted melt treatment can influence the solidification manner, development of microstructural characteristics and finally achieving mechanical properties of the alloy in accordance to corresponded casting geometry and/or technology application
Appropriate mathematical model for stress calculation based on the measured values of deformation and temperature changes
No full textPresented mathematical model determines the stresses depending on the measured temperature
changes and the associated deformations of the samples. Investigations were conducted by tensile
testing machine Zwick 50 kN on the samples from low-carbon niobium microalloyed steel. The values
of measured parameters were determined by using the methods of thermography and digital image
correlation. The model is formulated on the basis of a multiple regression analysis of the relations
between measured and calculated parameters. Verification and validation of the model showed a
good agreement between the model and the system modeled
Influence of Microstructure Development on Mechanical Properties of AlSi7MgCu Alloy
No full textThe design of materials through the selection of the chemical composition, thermodynamic modelling, melt treatment, correctly developed casting technology followed by adequate heat treatment could improve casting properties. A wide range of complex reactions and intermetallic phases occurs due to numerous alloying (Si, Mg, Cu) and trace elements (Fe, Mn) interaction. Determination of solidification sequence was performed by modeling of equilibrium phase diagram, simultaneous thermal analysis and metallographic investigations. Microstructure revealed needle-like Al5SiFe and Chinese script phase Al15(Fe,Mn,Cu)3Si2 enriched in copper. Copper addition resulted in formation of compact complex intermetallic phases Al5Cu2Mg8Si6 and Al8FeMg3Si6. Solidification ended with secondary eutectic phases Mg2Si and Al2Cu. Wide spectra of favourable intermetallic phases comprehend to the tensile mechanical properties development already in as-cast state. Comparison of yield and tensile strength with commonly used AlSi7Mg alloy indicates significant increase of investigated properties for innovative chemistry of AlSi7Mg(Cu) alloy in as-cast stat
Electrochemical and corrosion behaviour of copper shape memory alloy in NaCl solution
Get PDFThis paper presents a review of electrochemical and corrosion investigations on behaviour of CuAlNi and CuAlMn alloys in NaCl solutions, which were carried out within the framework of the project IP-2014-09-3405“ Design of microstructure and functional properties of copper-based shape memory alloys”, supported by the Croatian Science Foundation. The influence of alloys heat treatment on their corrosion behaviour was investigated, as well as the influence of chloride concentration, pH values and electrolyte temperatures. Cu-shape memory alloys were produced by continuous vertical casting and melt spinning method. Investigations were conducted by electrochemical methods such as open circuit current measurement method, electrochemical impedance spectroscopy method, linear and potentiodynamic polarization. Corroded specimens characterization was obtained by optical and scanning electron microscope. Analysis of the corrosion product composition was carried out by EDS method
Thermal analysis of biocompatible materials for tissue engineering
Get PDFTkivno inženjerstvo pruža velike mogućnosti u razvoju umjetnih organa, osobito bioloških regenerativnih materijala, kao što su hrskavica, kosti i koža. Dizajniranje odgovarajućih biorazgradljivih i biokompatibilnih materijala te praćenje biokemijskih i fizikalnih svojstava, kao i rasta stanica, omogućuje generiranje nadomjestaka koji mogu obnoviti ili znatno poboljšati funkciju oštećenih tkiva.
U ovom radu, istražen je utjecaj različite topografije elektroispredenih polimernih nosača polikaprolaktona (PCL) na uspješnost zasijavanja i rasta stanica. Kolektori su dizajnirani programom 123D Design te su zatim 3D printani. Nosači polikaprolaktona i antibiotika Cefuroxima, CFU®, pripremljeni su elektroispredanjem, u koncentracijama antibiotika, 14 % PCL + 15 % mas. i 14 % PCL + 20 % mas.CFU®. Morfološka struktura pripremljenih nosača prije i nakon zasađivanja HeLa stanica, praćena je skenirajućom elektronskom mikroskopijom (SEM), a biofunkcionalnost nosača ispitana je MTT testom. Temperature kristalizacije (Tk) i taljenja (Tm) PCL/CFU® nosača te stupanj kristalnosti (c) određeni su diferencijalnom pretražnom kalorimetrijom (DSC), dok je toplinska stabilnost materijala praćena tehnikom termogravimetrije (TG). Dobiveni rezultati mikrostrukture nosača korelirani su s rezultatima dobivenih temperatura transformacija te koncentracijom antibiotika, kao i rasprostranjenošću i rastom stanica na nosaču.Tissue engineering provides a great opportunities in the development of artificial organs, especially biological regenerative materials, such as cartilage, bone and skin. Designing the appropriate biodegradable and biocompatible materials and investigation of their biochemical and physical properties as well as cell growth factors, makes it possible to generate substitutes that can restore or substantially improve the function of damaged tissues.
In this paper, the effect of different topographies of electrospun Polycaprolactone fibrous carrier on the incorporation and cell growth was investigated. Polymer carriers with different structure and porosity, have been prepared by electrospinning of PCL/CEFUROXIM® (CFU®) solution at the designed and 3D printed collectors. Polymer solution was prepared with different concentrations of antibiotic CFU®, 15 and 20 %wt. Fibrous morphology was followed by scanning electron microscopy (SEM), while biocompatibility was detected by MTT test. Melting (Tm) and crystallization (Tc) temperatures of PCL/CFU® as well as degree of crystallinity (c) were determined by differential scanning calorimetry (DSC), while thermal stability of material was obtained by thermogravimetry (TG). Results of PCL/CFU® carrier microstructure were correlated with transformation temperatures and antibiotic concentrations as well as cell growth
Influence of Cu on the microstructure development of AlSi7MgCu
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
"Zbornik sažetaka 18. Međunarodnog savjetovanja ljevača: Suživot znanosti o materijalima i održive tehnologije u ekonomskom rastu"
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.
The importance of coexistence of material science and sustainable technology in economic growth reveals in collaboration between small and medium enterprises’ (SMEs´), industry and higher education institutions (HEI). International Foundrymen Conference organized by University of Zagreb Faculty of Metallurgy, Sisak, Croatia in cooperation with University of Ljubljana Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia, University North, Koprivnica, Croatia, Technical University of Košice Faculty of Materials, Metallurgy and Recycling, Košice, Slovakia, and ELKEM ASA, Norway found its significant position due to aforementioned reasons. Coexistence of material science and sustainable technology in economic growth 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 18th 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
Book of Abstracts; 18th International Foundrymen Conference: Coexistence of Material Science and Sustainable Technology in Economic Growth; Student’s section
Get PDFMetalurgija je specifično polje koje se bavi dizajnom, razvojem i karakterizacijom materijala od onih svakodnevnih koji nas okružuju u našim domovima, radnim mjestima, ali i materijala s posebnim zahtjevima za specifične namjene poput onih za automobilsku ili svemirsku industriju. Pritom treba poznavati i proizvodne procese. Kroz ove prethodne spoznaje provlači se oporaba i zbrinjavanje metalnih materijala i otpada iz proizvodnje kojim se bavi Industrijska ekologija. Industrijske djelatnosti, koje se utvrđuju kao strateške djelatnosti u Republici Hrvatskoj su Lijevanje metala i Proizvodnja gotovih metalnih proizvoda, prepoznate kao „pokretači gospodarskog rasta“ jer se od njih očekuje da ostvaruju veće stope rasta i zapošljavanja. Sinergijom istraživanja u metalurgiji i drugim poljima tehničkih znanosti poput strojarstva izrazito se doprinosi razvoju i karakterizaciji tehničkih materijala te potiče razvoj tehnologija i njihova optimizacija. Korelacijom inženjerstva tehničkih materijala utemeljenog na znanju i visoko tehnoloških rješenja odvija se transfer znanja interakcijom tvrtki i visokoškolskih institucija. Osim navedenog, a uvažavajući vještine i znanja stečene u praksi Fakulteti prepoznaju i organiziraju radionice, predavanja i prezentacije radi transfera znanja i iskustva stručnjaka iz industrije usmjerenih prema nastavnicima radi podizanja kompetencija, ali i studentima radi stjecanja specifičnih znanja i vještina. Visokoškolsko obrazovanje na Metalurškom fakultetu, ali i drugim suradnim ustanovama koncipirano programima i ishodima učenja zasniva se, između ostalog i na poticanju znanstvenoistraživačkog rada studenata s primijenjenim temama, kako bi ambiciozni i kreativni mladi ljudi postali samostalni rješavatelji problema, razvijajući i podupirući njihovu znatiželju, analitičnost, komunikativnost: Kako bi postali diplomci kakve želi tržište rada!Metallurgy, as a specific field of technical sciences, deals with the design, development and characterization of everyday materials in our homes, workplaces, as well as materials with special requirements for specific applications such as those for the automotive or space industry. Knowledge about manufacturing processes should also be acquired. The recovery and disposal of metal materials and waste from the production is underlined as a prerequisite knowledge. 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. The synergy of research in metallurgy and other fields of technical sciences, such as mechanical engineering, is particularly beneficial for the development and characterization of engineering technical materials and encourages the development of sustainable technologies and theirs optimization. Correlation of engineering of knowledge-based technical and high technological solutions is the transfer of knowledge through interaction between economy and higher education institutions. In addition to this, recognizing the skills and knowledge acquired in practice, the faculties recognize and recognize workshops, lectures and presentations for the transfer of knowledge and experience from industry-oriented teachers to raise competences, but also to students to acquire specific knowledge and skills. Higher education at the Faculty of Metallurgy, but also at the other HEIs´ conceived through the program and the learning outcomes, is based, inter alia, on promoting students scientific and research work on applied topics, enabling ambitious and creative young people to become independent problem solvers, developing and supporting their curiosity, analytics and communication: Graduates like the labour market needs
The impact of multiwall carbon nanotubes on the photocatalytic properties of imobilizied TiO2
Get PDFIndustry development, Earth’s population growth, ever increasing need for greater pharmaceuticals production causes irreversible changes in the environment. Photocatalysis is a process that leads to complete decomposition of pharmaceuticals to non-hazardous degradation products under the influence of solar radiation in the presence of a photocatalyst. A photocatalyst, such as titanium dioxide (TiO2), is required for photocatalysis. The efficiency of using TiO2 is limited due to the high energy banned zone (3-3.2 eV) so only UV-A light, which makes up 5% of solar radiation, activates the photocatalyst. In order to overcome the problem of prohibited zones and to shift the light response threshold of TiO2 into the visible part of the spectrum, different methods can be used. One of the methods showing the potential is the use of multiwall carbon nanotubes (MWCNT). In this paper a TiO2 / MWCNT composites with various concentrations of MWCNT were prepared. The concentrations of MWCNT ranged from 1.5, 5, 10, 25, 50 and 100 wt. % MWCNT relative to the mass of TiO2. It was observed that the concentration of MWCNT affects the photocatalytic activity of the composite obtained. Photocatalytic activity was followed by a degradation of salicylic acid, in a pilot reactor followed by UV-ViS spectrometry, as a modal solution and an example of a pharmaceuticals present in the water. The prepared catalysts were characterized by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectroscopy (EDX)