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Hydrometallurgical processing of the copper concentrates is a promising alternative to the conventional pyrometallurgical production of copper due to significantly lower environmental impact, capital and operational costs. Development of the hydrometallurgical process for copper recovery from mineral concentrate requires extensive work in testing and optimization of operational parameters from laboratory to semi-industrial scale. Mathematical modelling of the copper leaching process can save human labour and time. Leaching of copper from chalcopyrite concentrate using sulphuric acid and sodium nitrate as an oxidant was tested, and the influence of temperature, particle size, stirring speed and concentrations of sulphuric acid and sodium nitrate were evaluated. Obtained results showed that increasing temperature and concentrations of sulphuric acid and sodium nitrate increase the leaching degree of copper, while increasing particle size and stirring speed reduce copper extraction. In this paper, second-order polynomial models (SOP) were applied to experimental data. Presented results show that mathematical models fit experimental data. The conclusion is that SOP models are a promising tool to be used for modelling leaching processes of metals.

Izrada jednog umetničkog dela obično uključuje brojne različite tehnologije. To podrazumeva da je za razumevanje eventualno prisutnih nepravilnosti potrebno znati puno tehničkih detalja. Tehnologija lemljenja je jedna od njih, ispitivanje integriteta, takođe. Tehnologija lemljenja, uopšte, se razvijala na empirijski način, uglavnom pokušajima i greškama. Osnovnu teškoću čini realna situacija, koja je veoma složena, usled prisustva velikog broja uticajnih veličina, neke od njih se ne mogu lako prepoznati. Veliki problem je pojava pukotina u periodu posle čišćenja, tj. po završetku lemljenja, a to znači nekada posle više godina ili decenija. Dobar zalemljeni spoj mora biti valjano fizički i hemijski spojen. Jedna od primenljivih metoda ispitivanja je radiografsko ispitivanje, kada debljina ispitivanih delova obično ne predstavlja problem. Ovde izvedena radiografska ispitivanja su nagovestila prisustvo nekih indikacija samo na listovima. Penetranstsko ispitivanje je sledeći korak za ispitivanje površine. Registrovanje indikacija i njihovo lociranje su neophodni koraci u svakom daljem pristupu u cilju uklanjanja takvih diskontinuiteta. Izbor metode reparacije uvek je poseban problem, dakako u celoj tehnici, a posebno na osetljivim umetničkim predmetima. Svako delovanje u reparaciji ili restauraciji može dovesti do manje ili više vidljivih tragova. Neodgovarajuća delovanja mogu dovesti do manje ili više vidljivih tragova. Ovde je pokazana jedna nepravilnost (pukotina) na zalemljenom listu, na jednoj umetničkoj stonoj lampi., Making of an artistic piece usually includes a number of different technologies. It implies that for understanding of eventually present irregularities one should knows a lot of technical details. Brazing tehnology is one of them, inspection of integrity, also. Brazing technology generally has evolved on empirical manner, mainly by trial and error(s). The basic difficulty in this technology is that the real situation is highly complex due to the presence of large number of variables, some of them may not be easy to recognize. The great problem is the appearance of crack(s) in postcleaning periode, i.e after brazing is finished, it means over years or decades. A good braze joint must be both physically and chemically bounded. One of the available method for investigation is radiographic testing, when the thickness of testing components commonly does not represents a problem. Here provided radiographic testing has revealed the existence of some indications only at leaves. The indications usualy mean discontinuity in material homogenity. Penetrant testing is a next step for investigation of surface. Registration of indications and their locations are necessary steps in any further approach for removing such discontinuities. Choosing the repair method always is particular problem, however in entire technique, especially on sensitive artistic component(s). Every action in repairing or restauration may led to more or less visible traces. Unadequate actions may permanently change the appearance or usage of treated artefact. Here is shown one irregularity (crack) at one brazed leaf from an artistic desk lamp.

U istraživačkom radu opisan je komercializovan reciklažni proces prerade otpadnog rastvora iz postrojenja za proizvodnju sijaličnih vlakana od volframa radi izdvajanja molibden (VI)-oksida i njegovom daljem iskorišćavanju kao legirajućeg agensa sivog liva. U prvom delu izvršena je neutralizacija utrošene kiseline, koja u sebi sadrži izvesne količine molibdena, uz pomoć rastvora amonijaka, a potom kristalizacija i filtracija amonijum-molibdata, njegovo sušenje i prženje u cilju dobijanja praha molibdentrioksida tehničke čistoće (maseni udeo molibdena 59,2 mas%). U drugom delu izvršeno je legiranje sivog liva uz pomoć MoO3 u indukcionoj peći. Finalni proizvod je legura železa sa povećanom tvrdoćom uz postignut visok stepen usvajanja molibdena u leguri (čak do 86%)., The present work reports the commercialization of a recycling process of spent acid from filament tungsten wire plant to recover molybdenum (VI)-oxide and further utilizing this product for alloying cast iron. First part of the process consists of ammonia gas neutralization of spent acid containing molybdenum, crystallization and filtration of ammonium molybdate, drying and roasting to produce a commercial grade molybdic-trioxide powder (molybdenum mass fraction 59.2 mas%). Second part of the process consists of grey cast alloying with MoO3 in inducing furnace. Final product was hardened iron alloy with high yield of molybdenum recovery (up to 86 %).

Making of an artistic piece usually includes a number of different technologies. It implies that for understanding of eventually present irregularities one should knows a lot of technical details. Brazing technology is one of them, inspection of integrity, also. Brazing technology generally has evolved on empirical manner, mainly by trial and error(s). The basic difficulty in this technology is that the real situation is highly complex due to the presence of large number of variables, some of them may not be easy to recognize. The great problem is the appearance of crack(s) in postcleaning periode, i.e after brazing is finished, it means over years or decades. A good braze joint must be both physically and chemically bounded. One of the available method for investigation is radiographic testing, when the thickness of testing components commonly does not represents a problem. Here provided radiographic testing has revealed the existence of some indications only at leaves. The indications usualy mean discontinuity in material homogenity. Penetrant testing is a next step for investigation of surface. Registration of indications and their locations are necessary steps in any further approach for removing such discontinuities. Choosing the repair method always is particular problem, however in entire technique, especially on sensitive artistic component(s). Every action in repairing or restauration may led to more or less visible traces. Unadequate actions may permanently change the appearance or usage of treated artefact. Here is shown one irregularity (crack) at one brazed leaf from an artistic desk lamp., Izrada jednog umetničkog dela obično uključuje brojne različite tehnologije. To podrazumeva da je za razumevanje eventualno prisutnih nepravilnosti potrebno znati puno tehničkih detalja. Tehnologija lemljenja je jedna od njih, ispitivanje integriteta, takođe. Tehnologija lemljenja, uopšte, se razvijala na empirijski način, uglavnom pokušajima i greškama. Osnovnu teškoću čini realna situacija, koja je veoma složena, usled prisustva velikog broja uticajnih veličina, neke od njih se ne mogu lako prepoznati. Veliki problem je pojava pukotina u periodu posle čišćenja, tj. po završetku lemljenja, a to znači nekada posle više godina ili decenija. Dobar zalemljeni spoj mora biti valjano fizički i hemijski spojen. Jedna od primenljivih metoda ispitivanja je radiografsko ispitivanje, kada debljina ispitivanih delova obično ne predstavlja problem. Ovde izvedena radiografska ispitivanja su nagovestila prisustvo nekih indikacija samo na listovima. Penetranstsko ispitivanje je sledeći korak za ispitivanje površine. Registrovanje indikacija i njihovo lociranje su neophodni koraci u svakom daljem pristupu u cilju uklanjanja takvih diskontinuiteta. Izbor metode reparacije uvek je poseban problem, dakako u celoj tehnici, a posebno na osetljivim umetničkim predmetima. Svako delovanje u reparaciji ili restauraciji može dovesti do manje ili više vidljivih tragova. Neodgovarajuća delovanja mogu dovesti do manje ili više vidljivih tragova. Ovde je pokazana jedna nepravilnost (pukotina) na zalemljenom listu, na jednoj umetničkoj stonoj lampi.

The present work reports the commercialization of a recycling process of spent acid from filament tungsten wire plant to recover molybdenum (VI)-oxide and further utilizing this product for alloying cast iron. First part of the process consists of ammonia gas neutralization of spent acid containing molybdenum, crystallization and filtration of ammonium molybdate, drying and roasting to produce a commercial grade molybdic-trioxide powder (molybdenum mass fraction 59.2 mas%). Second part of the process consists of grey cast alloying with MoO3 in inducing furnace. Final product was hardened iron alloy with high yield of molybdenum recovery (up to 86 %).

High toxicity of lead and damaging effects on the environment resulted in its prohibited use in electronic materials (RoHS Directive from 1 July 2006 in the EU). Therefore, great effort has been made on the development of new Pb-free soldering and brazing materials [1-5]. The Bi–Cu–Ni ternary system belongs to the group of potential Cu-Ni-based advanced lead-free solder materials for high temperature application [6-8]. The results of phase equilibria investigation of the alloys selected in the Bi-Cu0.75Ni0.25 section from bismuth corner with molar ratio Cu:Ni = 3:1, are presented in this paper. The investigations were performed using DTA/DSC experimental methods, while thermodynamic calculation was done according to the CALPHAD method using PANDAT software. The results of the DTA/DSC heating measurements of the chosen samples in the Bi-Cu0.75Ni0.25 section, including liquidus temperatures and other phase transition temperatures are presented in graphical abstract. The phase diagram of the investigated Bi-CuNi section has been calculated using PANDAT software and is presented in graphical abstract, together with experimentally determined DTA/DSC points. It could be noticed that calculated phase diagram is in good agreement with DTA/DSC experiments.

Ispitivana legura zlata oznake 585, posmatrana u ovom radu je najčešće korišćena legura u juvelirskoj proizvodnji. Nedovoljno podataka, čak i danas, postoji oko proizvodnih postupaka legura zlata, uključujući režime topljenja, valjanja i termičke obrade. Strukture kompleksnih legura, kao što je ovde korišćena legura, su manje poznate ili izučavane. Principijelno, dijagram stanja sistema Au-Ag-Cu je poznat, kao (meta)stabilni dijagram. Ali posle relativno brzog hlađenja rastopa za vreme livenja obrazuju se polikristalna zrna, koja nisu nastala u ravnotežnim uslovima. Takav polikristalni materijal često se podvrgava valjanju radi dobijanja željenog oblika (polu)proizvoda. Ovi procesi, livenja i valjanja, pokazuju uticaj na konačnu strukturu, takođe i na osobine ovako tretirane legure. Strukturne promene kao i dobijene faze u procesima obrade legure zlata 585 još uvek nisu adekvatno ispitane. U ovom radu prikazani su neki rezultati izvršenih rendgenografskih ispitivanja nakon hladnog valjanja trake. Ispitivanja su izvršena na odlivcima dimenzija 4,5x50x50mm, koji su podvrgavani plastičnoj preradihladno valjanje do debljine trake od 1,5 mm, međufazno odžareni i završno izvaljani do debljine od 0,5mm, uz visinsku redukciju od 66,7%., Here is investigated an golden alloy 585 as one of widely used gold alloy in jewelry production. Insufficient data, even in nowadays, exist about the production schedule of gold alloys, including melting, rolling and heat treatment regimes. The structures of complex alloys, such as used golden alloy, are less known and/or investigated. Principally, the constitutional diagram of Au-Ag-Cu system is known, as a (meta)stable equilibrium diagram. But, after relatively fast cooling from liquid state during casting will be obtained polycrystalline grains, different from equilibrium conditions. Such polycrystalline material frequently undergoes to rolling for obtaining a desired shape of (semi)product. Those processes, casting and rolling, will show the influence on the final structure to be obtained, also on properties of such treated alloy. The structural changes and obtained phases in metal working processes of 585 gold alloy still are not well examined, so here is provided an XRD examination after heavy reduction at cold rolling of a strip. The castings were in the flat form in dimension of 4,5x50x50mm, than cold rolled to 1,5mm, intermediate annealed and finally cold rolled to thickness of 0,5mm with height reduction of 66,7%.

For investigation of artistic components, generaly, there are many developed methods, but a lot of them still are not fully reliable or standardized. One of the available method for such investigation is radiographic testing, when the thickness of testing components does not represents a problem, whatever if the great or small thickness exists. Here is tested an artefact in the shape of desk lamp. The chemical composition of the body is analysed by using XRF spectrography while the radiographic transparent testing is applied through the whole body of the lamp. The body of this desk lamp is produced by casting, using the precise casting method, while other decorative ornaments were shaped by hammering. The fastening of those components is provided by brazing or mechanically. The plastic deformation is designated as method for shaping of thin elements – here leaves. The radiographic testing has revealed the existence of some indications only at leaves produced by hammering. The indications usualy mean discontinuity in material homogenity. Registration of indications and their locations are necessary steps in every further approach for removing such discontinuities. Chossing the repair method always is particular problem, however in entire technique, especially in sensitive artistic component(s). Every action in repairing or restauration may led to more or less visible traces. Unadequate actions may permanently change the appearance or usage of treated artefact., Za ispitivanje umetničkih predmeta, uopšte, razvijene su brojne metode ali sve te metode još uvek nisu potpuno pouzdane ili standardizovane. Jedna od primenljivih metoda za ovakva ispitivanje je radiografsko ispitivanje, kada debljina ispitivanih delova ne predstavlja problem, bilo da se radi o velikoj ili maloj debljini. Ovde je ispitivan jedan umetnički predmet u obliku stolne lampe. Hemijski sastav tela je analiziran korišćenjem rendgenske spektrografske analize (XRF) dok je rendgensko prozračivanje upotrebljeno za snimanje celog tela lampe. Telo lampe je proizvedeno livenjem, korišćenjem metode preciznog liva, dok su ostali dekorativni ornamenti oblikovani kovanjem. Pričvršćivanje ostalih komponenti je izvedeno lemljenjem ili mehanički. Plastično deformisanje je označeno kao metoda oblikovanja tankih elemenata – ovde su to listovi. Radiografsko ispitivanje je otkrilo prisustvo izvesnih indikacija samo na listovima izrađenih kovanjem. Indikacije obično označavaju prekid u homogenosti materijala. Registrovanje indikacija i njihovo lociranje su neophodni koraci u svakom daljem pristupu u cilju uklanjanja takvih diskontinuiteta. Izbor metode repariranja uvek je poseban problem, dakako u celoj tehnici a posebno pri ispitivanju umetničkih komponenti. Svaka akcija u reparaciji ili restauraciji može dovesti do manje ili više vidljivih tragova. Neadekvatne akcije mogu za stalno da promene izgled ili upotrebu tretiranog artefakta.

U disertaciji je razvijena nova eksperimentalna postavka za merenje graničnih uslova pri livenju u peščanim kalupima. Utvrđeno je da se uvođenjem pojma prividne toplotne difuzivnosti materijala kalupa može poništiti greška pozicioniranja termoparova i time smanjiti greška procene graničnih uslova. Dodatno, pokazano je da proces izdvajanja intermetalnih jedinjenja tokom procesa očvršćavanja kalupa može uticati na vrednosti graničnih uslova. Razvijena je i nova empirijska korelaciona funkcija kojom se može opisati promena vrednosti koeficijenta prenosa toplote između kalupa i odlivka., In this study a new experimental technique and apparatus for estimation of boundary conditions in sand casting process were developed. It is shown that thermocouple positioning errors can be nullified by introducing a concept of apparent heat diffusivity of the mold material. In this way, total error of the heat transfer estimation can be reduced. Additionally, it was found that the process of precipitation of intermetallic compounds can influence the value of achieved metal-mold heat transfer. A novel empirical correlation function is proposed. This function has the ability to accurately describe the change in interfacial heat transfer with the casting surface temperature.

The effect of tempering at 450 - 650A degrees C of different duration on mechanical properties and microstructure of a cast low-alloy steel is investigated. The ultimate rupture strength, the yield strength, the elongation and the Vickers hardness of the steel are determined. Metallographic analysis is performed.

Eksperimentalnim istraživanjima su definisani kako tehnološka šema dobijanja kalcijuma iz krečnjaka aluminotermijskim procesom tako i osnovni radni parametri pojedinih tehnoloških faza. Uzorci krečnjaka koji su korišćeni u radu imaju visok sadržaj Mg, Na i K. Rendgenska analiza je pokazala da uzorci uglavnom sadrže kalcit i u manjoj količini dolomit. Na početku je ispitan uticaj temperature, vremena i granulometrijskog sastava na kalcinaciju kalcijum-karbonata. Vreme trajanja procesa disocijacije je 10-15 min na 1200 °C i povećava se sa smanjenjem veličine čestica do 5 mm. Nakon toga, ispitana je aluminotermijska redukcija kalcijum-oksida. Na temperaturi od 1200 °C i vakuumu od 3 KPa proces redukcije se završava za 2 h. Analiza hemijskog sastava kalcijum-oksida i kalcijuma pokazuje povećan sadržaj magnezijum-oksida i oksida alkalnih metala, posebno natrijuma., We present experimental investigations that define both the technological scheme of calcium production from limestone by aluminothermic process and the basic operating parameters of the particular technological phases. The limestone with high content of Mg, Na and K was used in the study. X-ray analysis reveals that the samples contain mainly calcite with small amount of dolomite. At first, the effects of temperature, time and granulometry on the calcium carbonate calcination were examined. The dissociation process was completed in 10-15 min at 1200 °C, and the dissociation rate increased with decreasing particle size down to 5 mm. Afterwards, the aluminothermic reduction process of calcium oxide was investigated. At a temperature of 1200 °C and vacuum of at least 3 kPa, the reduction process completed within 2 h. The chemical composition of calcium oxide and calcium showed increased content of magnesium oxide and alkaline oxides (especially sodium).

U radu je prikazana mogućnost dobijanja homogenije mikrostrukture i ravnomernije raspodele legirajućih elemenata Zn i Mg u aluminijumskoj leguri EN AW 7075, prilikom livenja u prisustvu elektromagnetnog polja. Ispitana su i mehanička svojstva uzoraka koji su odliveni bez i sa elektromagnetnin poljem. Rezultati pokazuju da se livenjem u elektromagnetnom polju postižu prednosti u odnosu na klasičan postupak livenja aluminijumskih legura., The microstructure and the mechanical properties of the samples obtained by conventional vertical continuous casting and electromagnetic casting of 7075 aluminum as-cast alloy were investigated. The better surface quality, more homogeneous alloying elements distribution and hence the microstructure and better mechanical properties were obtained in samples casted with electromagnetic field (EMF) compared with samples casted without EMF. The microstructure was analyzed by optical microscope and the variation of alloying elements, Zn and Mg, through the sample cross section was examined by chemical analysis. The mechanical properties of samples casted with and without electromagnetic field were determined using computerized materials testing machine Zwick/Roel Z 100.

The processes that take place at the liquid metal-sand mold interface during the casting and crystallization of metal were studied in this paper. The mold was made using the CO2 - Method, with the addition of active components, such as: MgO, TiO2, AIK(SO4)(2) and Na2SO4. At the liquid steel pouring temperature, these active components undergo decomposition in the mold, caused by heat release during pouring, Crystallization and cooling of castings. Silicates, which have an important influence on casting surface quality, are formed as a result of the interaction between the mould material and liquid steel.

Hidroksiapatitna (HAp) prevlaka je atmosferskim (APS) plazma-sprej postupkom naneta na metalne uzorke napravljene od 316LVM čelika, namenjenog za izradu implantata u ortopedskoj hirurgiji. Razvoj savremenih ortopedskih implantata podrazumeva da se na podlogu od bioinertnih legura nanosi bioaktivna HAp prevlaka. Sintetički HAp je hemijski sličan onom koji čini mineralnu građu kostiju i zuba. Zahvaljujući dobrim bioaktivnim svojstvima hidroksiapatitnih prevlaka moguće je obrazovanje stabilne veze između koštanog tkiva i implantata. U radu je prikazana mogućnost primene APS postupka za dobijanje stabilnih HAp prevlaka na uzorcima od nerđajućeg čelika 316LVM. Praćena je mikrostruktura i poroznost prevlake metodom optičke mikroskopije i skenirajuće elektronske mikroskopije. Ca/P odnos je određen EDS analizom., For decades, the standard metallic materials for hip implants, besides the 316LVM stainless steel, were titanium- and cobalt/chromium-based alloys. Although bioinert, due to their corrosion resistance, they are not biocompatible. Contemporary surgical implants are no longer made solely from bioinert metals anymore, but with deposited bioactive hydroxyapatite (HAp) coatings. Hydroxyapatite is chemically identical with the mineral constituent of bones and teeth, which, besides its biocompatibility, provides bioactivity as well. The HAp limitations are, however, weak tensile strength and low fatigue resistance for long term loadings, if used alone. This is the reason for HAp to be deposited onto the surgical implant, and to enable its bioactivity, which means intergrowth with bones, and therefore the long-lasting and mechanical stable non-cemented prosthesis. This is important predominantly because of the need for such prostheses for younger population and a better life quality. There are several contemporary techniques that have been used for deposition of these coatings onto the metal implant. The possibilities of atmospheric plasma-spraying for obtaining stable HAp coatings on 316LVM stainless steel, ordinarily used as a standard material for hip implants production, are presented in this paper. The coatings of a commercially available hydroxyapatite powder were plasma-sprayed onto specimens of medical grade 316LVM stainless steel under various operating conditions. Optical microscopy was used for microstructure and porosity characterization, while the coating morphology and Ca/P ratio were analyzed using an SEM equipped with EDX. The coating microstructure varied from a porous to a glassy structure, depending on the operating conditions and coating thickness. Coating porosity was determined to be at the lower required limit requested for the bone-coating intergrowth possibility, but nevertheless adhesion measurements showed good results. The Ca/P ratio was determin

U radu su prikazani osnovi elektromagnetnog postupka livenja aluminijumske legure EN AW 7075 kao i rezultati mehaničke karakterizacije otkovka od ove legure koja je dobijena livenjem klasičnim polukontinualnim postupkom livenja i livenjem pod dejstvom elektromagnetnog polja sa dve različite frekvence. Rezultati pokazuju da uzorci otkovaka dobijeni od legure koja je livena u elektromagnetnom polju imaju zadovoljavajuće vrednosti mehaničkih svojstava i da se pravilnim izborom radnih parametara livenja mogu stvoriti uslovi za skraćenje tehnološkog postupka prerade ove legure., The electromagnetic casting process fundamentals of EN AW 7075 Al-alloy casting, as well as the mechanical characterization results of this alloy forgings are presented in this paper. Forgings are obtained from the alloy casted by classical semi-continuous casting process and by electromagnetic casting process using two different frequencies. Results reveal that forgings obtained from the alloy casted by electromagnetic casting process have adequate values of mechanical properties and that proper choice of operating parameters can lead to shortening of this alloy processing.

Od vrste i kvaliteta kalupne mešavine odnosno njenog ponašanja u dodiru sa stopljenim metalom u realnim uslovima najviše zavise intenzitet, i uopšte razvoj, pojedinih procesa na graničnoj površini dodira metal-kalup. Značajno mesto u odigravanju procesa međusobnog delovanja livačkih kalupa i tečnog metala pored hemijskog, mineralnog sastava peska, vrste vezivnog sredstva imaju i dodaci kalupnim mešavinama. Ovi dodaci, tj aktivne komponente, uslovljavaju određene promene na povišenim temperaturama u samoj mešavini kao i njeno reagovanje sa površinskim slojem tečnog metala. Cilj ispitivanja je bio da se vidi u kolikoj meri sastav kalupne mešavine sa i bez dodatih-aktivnih komponenata utiče na površinu odlivaka., The intensity, and overall development of individual process on the metal-mould interface depend on the type and quality of mould mixture or its behavior in contact with the melted metal in real conditions. Important role in interaction between foundry moulds and liquid metals, in addition to chemical and mineral composition of sand, and a type of binding material, play also additives for mould mixtures. These additives, i.e. active components, provided some changes at elevated temperatures inside the mixture, as well as its reaction with the surface layer of liquid metal. The aim of this investigation was to determine how the composition of the mould mixture with and without active components affect the surface of castings.

Metalni implantati za ortopedsku hirurgiju izrađuju se najčešće od nerđajućeg čelika, legura na bazi titana, kobalta ili hroma, koje imaju odlične konstrukcione i mehaničke osobine i otporne su na koroziju. Ipak, ovakvi implantati poldožni su lokalnoj koroziji u ljudskom telu jer je zapaženo prisustvo njihovih metalnih jona u okolnim tkivima i telesnim tečnostima. Da bi se iskoristila prednost njihovih mehaničkih karakteristika, a postigla biokompatibilnost, moguće je na njihovu površinu naneti bioinertnu ili čak bioaktivnu prevlaku. Hidroksiapatit je poznat po svom bioaktivnom ponašanju, koje duguje hemijskoj istovetnosti sa ljudskim kostima. Elektroforetska deopzicija je relativno stara tehnika, koja je ovde primenjena uz upotrebu novog materijala - nanostrukturnog hidroksiapatita, kako bi se dobile ravnomerne i kompaktne hidroksiapatitne prevlake i tako prevazišla ograničenja prethodno korišćenih visokotemperaturnih tehnika nanošenja prevlaka i problemi sa složenim oblikom metalnog supstrata. Prevlake nanostrukturnog hidroksiapatita eletroforetski su deponovane na peskiranu površinu uzoraka od nerđajućeg čelika 316LVM, pri konstantnom naponu, za različito vreme deponovanja, a zatim su sinterovane u atmosferi argona na 1000oC. Toplotna stabilnost HAp praha prvo je ocenjena DTA/TG analizom u temperaturnom intervalu 23oC-1000oC. Za mikrostrukturnu karakterizaciju prevlake korišćen je SEM, a za određivanje faznog sastava XRD analiza., Surgical metallic implants are usually made of stainless steel, titanium- and cobalt/chromium- based alloys which have superior structural and mechanical properties, and are corrosion resistant. Nevertheless, they are susceptible to local corrosion in the human body, releasing metal ions into the nearby body tissue and fluids. Keeping the advantage of their mechanical properties, their biocompatibility can be achieved through deposition the bioinert or even bioactive coating onto their surface. Hydroxyapatite is known by its bioactive behavior, originating from its chemical identity with human bones. The electrophoretic deposition is rather old technique used here with a novel nanostructured hydroxyapatite powder to obtain uniform and dense hydroxyapatite coatings, to overcome the restrictions of previously used high temperature coating techniques and to overcome the complex geometry metallic substrate problems. The coating of nanosized hydroxyapatite was electrophoretically deposited on blasted surface of stainless steel 316LVM samples at constant voltage, for different deposition times and subsequently sintered in argon atmosphere at 1000 oC. The HAp powder thermal stability was initially assessed using DTA-TG analyses over the temperature range of 23oC-1000oC. The microstructure characterization of the coating was accomplished using SEM, and phase composition was determined by XRD.

High strength low-alloyed (HSLA) Cr-Mn-Si steels belong to a group of steels that can reach their full mechanical properties after quenching and tempering. Those properties depend both on the temperature and time of tempering. Knowing the tempering parameters, it is possible to reach the desired properties of the treated steel. Some results on investigating the Hollomon-Jaffe equation (in parametric form) application for tempering of HSLA steel, are shown in this paper. The experiments were performed in real production conditions, using a standard material. The quenching was performed at 870°C, the heating period was always 30 min, with subsequent cooling into the oil bath. The tempering was carried out in temperature range from 480 to 680°C, while tempering time varied from 15 min to 24 h. The degree of tempering is referred through the hardness values changing. The experimental results have shown a pretty well agreement to tempering parameters, included in Hollomon-Jaffe equation, for this kind of HSLA steel.

Proučavana je mikrostruktura odlivaka koji su dobijeni kontinuiranim livenjem Al legure EN AW 2024 čija se kristalizacija odvijala bez uticaja i pod uticajem elektromagnetnog polja malih frekvencija. Mikrostrukturna analiza pokazuje da se pod dejstvom niskofrekventnog elektromagnetnog polja dobija finija i po preseku homogenija mikrostruktura. S obzirom da su ovo kod nas prva primenjena istraživanja uticaja elektromagnetnog polja na proces očvršćavanja, rezultati jasno ukazuju u kom pravcu treba menjati radne parametre kako bi se dobili odlivci optimalnog kvaliteta., The results presented in this paper were obtained from microstructure examination of Al alloy 2024 ingots casted with or without low-frequency electromagnetic field. The microstructure characterization shows that it is possible to get finer and more homogeneous microstructure through the entire cross section of ingots casted with electromagnetic field, compared to ingots casted without electromagnetic field. Although, this is our first examination into the effect of electromagnetic field on process of solidification, it is obvious in which way the operation parameters should be varied in order to get a good quality of ingots.