Aluminum alloys are widely applied in automotive, aircraft, food, and building industries. Multicomponent technical AlSi9MgMn alloy is primarily intended for high cooling rate technology. Controlled ...addition of alloying elements such as iron and manganese as well as magnesium can improve mechanical and technological properties of the final casting depending on the cooling conditions during solidification. The aim of this investigation is the characterization of AlSi9MgMn alloy microstructure and mechanical properties at lower cooling rates than those for which this alloy was primarily developed. Thermodynamic calculation and thermal analyses revealed solidification sequence in correlation to the microstructure investigation as follows: development of primary dendrite network, precipitation of high temperature Al15(Mn,Fe)3Si2 and Al5FeSi phases, main eutectic reaction, precipitation of intermetallic Al8Mg3FeSi6 phase, and Mg2Si as a final solidifying phase. Influence of microstructure features investigation and cooling rate reveals significant Al15(Mn,Fe)3Si2 morphology change from Chinese script morphology at low, irregular broken Chinese script morphology at medium, and globular morphology at high cooling rate. High manganese content in AlSi9MgMn alloy together with high cooling rate enables the increase of Fe+Mn total amount in the intermetallic Al15(Mn,Fe)3Si2 phase and encourage favourable morphology development, all resulting in enhanced mechanical properties in as-cast state.
Powder Mo&O2 has an important role in the production of coatings with increased resistance to slide in conditions without the use of lubricants. Mo&O2 coatings have the low coefficient of friction ...and good abrasion characteristics in mechanical stresses. For the purpose of producing coatings of high hardness, Mo&O2 powder is plasma deposited with optimal parameters. The surface shape of oxide powder particles and the coating fracture surface are analysed by SEM, and the microstructure of layers is examined by light microscopy. The coating microstructure consists of Mo lamellae and MoO3 and MoO2 primary oxide thin films, which surround the Mo lamellae. The analysis of the obtained results showed that the Mo&O2 coating layers with the diffusion oxidized Mo particles have such a structure and mechanical characteristics which enable its application in working tools under the conditions of wear and sliding friction without lubricants. / Применение порошка Mo&O2 играет важную роль в процессе нанесения покрытия с повышенной устойчивостью к скольжению в бессмазочных условиях. Покрытия Mo&O2 обладают низким коэффициентом фрикции и высоким пределом прочности при механическом напряжении. В целях достижения наибольшей прочности покрытия, порошок Mo&O2 наносится методом плазменного напыления, с учетом оптимальных параметров. Характеристики состояния поверхности частиц оксидного порошка и поверхности излома покрытия установлены SEM методом. А микроструктура слоев нанесенного покрытия испытана методом световой микроскопии. Микроструктура покрытия состоит из ламелей Мо и тонких оксидных прослоек MoO2 и MoO3 вокруг ламелей Мо. Анализ полученных результатов доказал, что слои покрытия Mo&O2 с диффузионными оксидными частицами Мо обладают структурой и механическими характеристиками, позволяющими нанесение данного покрытия на поверхности рабочих участков в условиях износа и скольжения при бессмазочном трении. / Prah Mo&O2 ima značajnu ulogu u proizvodnji prevlaka sa povišenom otpornošću na klizanje u uslovima bez primene maziva. Prevlake Mo&O2 imaju mali koeficijent frikcije i dobre karakteristike na habanje pri mehaničkim naprezanjima. Radi proizvodnje prevlaka visoke tvrdoće, prah Mo&O2 je deponovan plazmom sa optimalnim parametrima. Karakterizacija oblika površine čestica oksidnog praha i površine preloma prevlake izvedena je metodom SEM, a mikrostruktura slojeva primenom svetlosne mikroskopije. Mikrostruktura prevlake sastoji se od lamela Mo i tankih filmova primarnih oksida MoO2 i MoO3 koje okružuju lamele Mo. Analiza dobijenih rezultata pokazala je da slojevi prevlake Mo&O2 sa difuziono oksidiranim česticama Mo imaju strukturu i mehaničke karakteristike koje omogućuju njenu primenu na površinama radnih delova u uslovima habanja i klizanja trenjem bez maziva.
ZrO2 stabilized with Y2O3 has superior and excellent physical properties compared to other modern ceramic materials. Due to its high biocompatibility, ZrO2 ceramics in the ZrO2 - Y2O3 system is ...widely used as a biomaterial in orthopedic surgery. ZrO2 - Y2O3 ceramics is widely applied in the production of the head of the hip, knee prosthesis, temporary holders, and more. ZrO2 is used for a total hip replacement (THR), for an artificial knee joint as well as for the application and development of other medical devices. In order to use ZrO2Y2O3 ceramics (YSZ) in biomedical substrates, it is necessary to deposit coating layers without defects. For the purpose of the deposition of a ZrO28wt.%Y2O3 ceramic coating with the best structural properties, the ZrO2Y2O3 / ZrO2Y2O3CoNiCrAlY / CoNiCrAlY coating system was tested. For financial reasons, the deposition was performed on a steel substrate by applying a CoNiCrAlY bond coating, which does not affect the structure and functionality of the ZrO2Y2O3 ceramic layer. The structure of the layers was tested by the method of light microscopy, and the surface of the upper ZrO28wt.%Y2O3 ceramic coating was tested by the method of scanning electron microscopy SEM. The obtained characteristics showed that the porosity content in the ceramic layer was not high and that micropores were uniformly distributed. The mechanical properties of the layers were assessed by testing microhardness using the method HV0.3 and tensile bond strength using tensile testing. The values of the microhardness of the ZrO28wt.%Y2O3 coating were satisfactory as well as the tensile bond strength of the coating system. / Керамика ZrO2 стабилизированная оксидом иттрия Y2O3 обладает наилучшими характеристиками по сравнению с иными современными керамическими материалами. Благодаря высокому проценту биосовместимости, керамика ZrO2 в системе ZrO2-Y2O3 широко применяется в качестве биоматериалов в ортопедической хирургии. Керамика ZrO2 используется в области протезирования, в частности, для изготовления головки бедренной кости, колени, временного протеза и пр. В области медицины ZrO2 широко используется в изготовлении протеза бедра (THR), коленного сустава, и иных медицинских аппаратов. Нанесение керамического покрытия ZrO2Y2O3(YSZ) на биомедицинские субстраты должно быть равномерным, а его слои без изъянов. Для нанесения керамического покрытия ZrO2Y2O3(YSZ), обладающего наилучшими структурными характеристиками была испытана система покрытий ZrO2Y2O3/ZrO2Y2O3CoNiCrAlY/CoNiCrAlY. В целях экономии, напыление выполнено на стальном субстрате связывающим покрытием CoNiCrAlY, не влияющим на структуру и функциональность керамического слоя ZrO2Y2O3. Структура слоев испытана методом оптической микроскопии, а поверхность ZrO28mas%Y2O3 испытана методом электронной микрографии SEM. На основании полученных характеристик установлено, что содержание порообразований в керамическом слое достаточно низкое, а микропоры равномерно распределены. Анализ механических характеристик покрытия проведен на основании испытаний микротвердости методом HV0.3 и прочности соединений методом растяжения. Значения микротвердости ZrO28mas%Y2O3 покрытия соответствуют требованиям, так же как и прочность связи покрытий. / Keramika ZrO2, stabilizovana sa Y2O3, ima superiorna i odlična fizička svojstva u poređenju sa drugim savremenim keramičkim materijalima. Zbog visoke biokompatibilnosti ona u sistemu ZrO2-Y2O3 ima široku primenu kao biomaterijal u ortopedskoj hirurgiji. Keramika ZrO2-Y2O3 najčešće se primenjuje za izradu glava kuka, proteza kolena, privremenih držača itd. ZrO2 je u kliničkoj upotrebi kao ukupna zamena kuka (THR), u zglobu veštačkih kolena, ali se koristi za primenu i razvoj drugih medicinskih uređaja. Da bi se keramika ZrO2Y2O3(YSZ) koristila na biomedicinskim substratima, neophodno je deponovati slojeve prevlake bez defekata. Radi depozicije keramičke prevlake ZrO28tež%Y2O3 sa najboljim strukturnim svojstvima, ispitan je sistem prevlaka ZrO2Y2O3/ZrO2Y2O3CoNiCrAlY/CoNiCrAlY. Zbog ekonomičnosti depozicija je izvršena na čeličnom supstratu uz primenu vezne prevlake CoNiCrAlY, što ne utiče na strukturu ifunkcionalnost keramičkog sloja ZrO2Y2O3. Struktura slojeva ispitana je metodom svetlosne mikroskopije, a površina gornje keramičke prevlake ZrO28mas%Y2O3 metodom skening elektronske mikroskopije (SEM). Na osnovu dobijenih karakteristika utvrđeno je da sadržaj poroznosti u keramičkom sloju nije bio visok i da su mikropore ravnomerno raspoređene. Procena mehaničkih osobina slojeva urađena je ispitivanjem mikrotvrdoće metodom HV0.3 i zatezne čvrstoće spoja ispitivanjem na zatezanje. Vrednosti mikrotvrdoće ZrO28mas%Y2O3 prevlake bile su zadovoljavajuće i zatezna čvrstoća spoja sistema prevlaka.
Mullite-zirconia composites were prepared by reaction sintering of alumina and zircon powder. Slip casting was also used to fabricate the composites. The effect of nano-TiO2 additions on their ...properties was investigated, and the results compared with using micro-sized TiO2 additions. The physical properties, phase composition, flexural strength and microstructure after firing at 1600 C were studied. The results showed that the flexural strength tended to increase with the addition of 0.5 wt% nano-TiO2, due to the formation of larger size rod-like ZrO2 and enhanced ceramic bonding between them.
U radu je analizirana vakuum plazma sprej prevlaka VPS – Cr3C2 - 25(Ni20Cr). Upotrebljen je komercijalni prah oznake Sulzer Metco Woka 7205. Prah je deponovan sa plazma pištoljem F4 na odstojanju ...substrata od 340 mm. Glavni cilj rada bio je da se na smanjenom pritisku inertnog gasa Ar eliminiše razgradnja primarnog karbida Cr3C2 u karbid Cr23C6 koji bitno umanjuje mikrotvrdoću i mehaničke karakteristike prevlake. Prevlaka je deponovana debljine od 100 do 120 µm na čeličnom substratu. Mikrotvrdoća prevlake ispitana je metodom HV0.3. Vrednosti mikrotvrdoće bile su u rasponu od 1248 do 1342 HV0.3. Čvrstoća spoja prevlake ispitana je metodom na zatezanje. Utvrđeno je da čvrstoća spoja između substrata i prevlake ima vrednost 89 MPa. Mikrostruktura prevlake ispitana je tehnikom svetlosne mikroskopije. Struktura prevlake sastoji se od osnove NiCr legure sa dominantnom primarnom karbidnom fazom Cr3C2. Pored Cr3C2 faze prisutna je i faza Cr7C3. Nagrizanje prevlake urađeno je reagensom 1HNO3: 4HCl: 4H2O koji prvenstveno rastvara Ni da bi se videla raspodela karbidne faze u prevlaci. Nagrizanjem prevlake reagensom utvrđeno je da je u slojevima prevlake u velikom udelu prisutna primarna nerazgrađena karbidna faza Cr3C2 koja prevlaci daje visoke vrednosti mikrotvrdoće. / This paper analyzes vacuum plasma spray VPS - Cr3C2 - 25(Ni20Cr) coatings. Commercial powder marked Sulzer Metco Woka 7205 is used. The powder is deposited with a plasma gun F4 at a distance of 340 mm from the substrate. The main objective of the study was to eliminate, at the reduced pressure of inert gas Ar, the degradation of primary Cr3C2 carbide into Cr23C6 carbide which significantly reduces the microhardness and mechanical properties of the coating. The coating is deposited with a thickness of 100 - 120 µm on a steel substrate. The microhardness of the coating was tested by HV0.3. The microhardness values were in the range of 1248 - 1342 HV0.3. The bond strength of the coating was tested by tension. It was found that the bond strength between the substrate and the coating has a value of 89 MPa. The microstructure of the coating was tested by the light microscopy technique. The structure of the coating consists of an NiCr alloy base with a dominant primary Cr3C2 carbide phase. In addition to the Cr3C2 phase, the Cr7C3 phase is also present. The coating etching was done with the reagent 1HNO3 : 4HCl : 4H2O that primarily dissolves nickel to enable the distribution of the carbide phase to be clearly seen in the coating. Etching the coating with this reagent revealed the presence of the largely undegraded primary Cr3C2 carbide phase which provides high hardness values to the coating. / В данной работе анализируется метод вакуумного плазменного напыления покрытия Cr3C2 - 25(Ni20Cr) с использованием промышленного порошкового состава Sulzer Metco Woka 7205 при применении плазматрона F4 на расстоянии 340мм от основания. Основной целью работы является проверка утверждения, что при пониженном давлении инертного газа исключается распад первичного карбида Cr3C2 до карбида Cr23C6, который значительно снижает микротвердость и механические свойства. Покрытие толщиной 100 – 120 µm наносилось на стальное основание. Испытания покрытия на микротведость проводились по методу HV0.3. Значения показателей микротвердости находятся в промежутке 1248 - 1342 HV0.3. Испытание адгезии покрытия к основанию проводилось методом натяжения, полученное в результате испытания значение составляет 89 MPa. Изучение микроструктуры покрытия, методом световой микроскопии показало, что покрытие состоит из основного сплава NiCr с преобладанием первичной карбидной фазы Cr3C2 и присутствием фазы Cr7C3. Травление покрытия проводилось с использованием реагента 1HNO3: 4HCl: 4H2O, растворяющего в первую кочередь никель, что позволяет увидеть распределение карбидной фазы в покрытии. Травление покрытия показало, что в слое преобладает карбидная фаза Cr3C2, обеспечивающая высокое значение микротвердости покрытия.
Namjena ove studije je ispitivanje ponašanja mikro strukture alatnoga čelika za rad na hladno Mat. No.1.2379 (ENX160CrMoV121; AISI D2) po pretaljivanju s preciznim pulsiranim Nd:YAG laserom. Zbog ...velike količine legirnih elemenata istraživani materijal spada u grupu vrlo teško zavarljivih alatnih čelika. Analiza je provedena na pojedinim pretaljenim točkama korištenjem specifi čnog oblika i parametara laserskog impulsa koji osiguravaju skrućivanje bez pukotina. Pretaljena područja su ispitivana mikroskopom, mjerenjem mikro tvrdoće, rendgenskom spektroskopijom i defrakcijskom metodom. Tretman laserom uzrokvao je brzo skrućivanje koja dovodi do formiranja fi ne dendritičke strukture s velikim udjelom zaostalog austenita što uzrokuje bitno smanjivanje tvrdoće.
Obrada metala intenzivnom plastičnom deformacijom (IPD) – odgovarajuća struktura i mehanička svojstva. IPD je postupak pretvorbe krupno u ultrafino zrnate (UFZ-a) metale i legure. Dobiveni UFZ ...materijal posjeduje oplemenjena mehanička i fizikalna svojstva, te su namjenjeni za široko komercijalno rabljenje. Ovaj članak s jedne strane daje osvrt na povijesni razvitak IPD-a postupka, a s druge strane djelomice ishodište za razvitak UFZ-a i njezine stabilnosti u trgovački čistom aluminiju, kao funkcija preoblikovanja i poslije deformacije primjenjenog žarenja.
Termički i mehanički parametri oblikovanja i stvaranje mikrostrukture trebaju biti što bliži realnim uvjetima. Test ravninskom tlačnom deformacijom i daljnja računalna simulacija omogućili su analizu ...kinetike rekristalizacije. Istraživanje raspodjele deformacijskih karakteristika u uzorku po rasterećenju provedeno je zajedno s analizom mikrostrukture čelika AISI 304 tijekom vrućeg oblikovanja. Dobiveni su podaci o veličini zrna uzorka ovisno o narinutoj deformaciji.
The presentation of this book emphasizes an exposition of the computational principles and the application of computational welding mechanics to practice. The objective in Computational Welding ...Mechanics is to extend the capability to analyze the evolution of temperature, stress and strain in welded structures together with the evolution of microstructure. Distortion caused by volumetric strains due to thermal expansion and phase transformations are a dominate load in the stress analysis. The microstructure evolution influences the constitutive equations. In particular, as the temperature changes from above the melting point to room temperature, the stress-strain relationship changes from linear viscous, to visco-plastic to rate independent plasticity. In high strength steels, transformation plasticity can have a major affect in reducing the longitudinal residual stress in welds. In the past twenty years the capability to analyze short single pass welds including the above physics has been developed. The software engineering to develop codes to solve these coupled problems has tended to be near the limit of what users and software developer can manage. The complexity has been too great to develop codes to deal with long multipass welds in complex structures. To deal with this problem, new software engineering methods and strategies have been developed, that are able to automatically create initial conditions, boundary conditions, adaptive mesh generation and manage time stepping. The input is a functional specification of the problem that includes a weld procedure, a weld path and a structure to be welded. The weld procedure contains weld parameters for each weld pass in a weld joint.