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Influence of melt treatment by inoculation on microstructure and mechanical properties development of AlSi12 alloy
Get PDFZahvaljujući širokoj lepezi povoljnih svojstava, aluminijske legure pronalaze primjenu u svim industrijskim granama. Radi poboljšanja mehaničkih, fizikalnih i korozijskih svojstva aluminijskih legura osnovnom elementu dodaju se legirajući elementi poput silicija, bakra ili magnezija te elementi u tragovima poput željeza, mangana, titana, bora, stroncija ili natrija. Njihov primarni utjecaj, ali i međusobna interakcija doprinijet će ciljanom razvoju mikrostrukture koja će indirektno utjecati na poboljšanje zahtijevanih svojstava. Važnu ulogu pritom ima i odabir tehnologije koja će utjecati na brzine hlađenja i/ili skrućivanja te pritom sinergijski s dodanim elementima činiti osnovu razvoja mikrostrukture i konačnu upotrebnu vrijednost odljevaka.
U ovome radu ispitana je EN AlSi12 (DIN 230) legura namijenjena visokotlačnom lijevanju. Proizvedena je i praćena kvaliteta AlSi12 legure s različitom obradom taline: AlSi12 s dodatkom modifikatora AlSr10 te AlSr12 s dodatkom modifikatora AlSr10 i cjepiva AlTi5B1. Hipoteza istraživanja bazira se na pretpostavci da se ciljanom obradom taline utječe na slijed skrućivanja, razvoj mikrostrukturnih značajki, a time i postignuta mehanička svojstva legure.Due to a wide array of favourable properties, aluminium alloys are used in all industrial branches. Elements like silicon, copper or magnesium, along with trace elements such as iron, manganese, titan, boron, strontium or sodium are added in order to improve mechanical, physical and corrosion properties of aluminium alloys. Their primary effect, as well as their interaction will lead to the development of microstructure, thus resulting in improvement of desired properties. The choice of technology which will impact the speed of cooling and/or solidification, along with making the base for the improvement of microstructure and final worth of the casts in synergy with added elements, is of great importance.
This paper examines EN AlSi12 (DIN 230) alloy intended for high pressure casting. Produced alloy AlSi12 with different way of melt processing was monitored for quality. Different ways of melt processing were AlSi12 with addition of AlSr10, and AlSr12 with addition of AlSr10 and AlTi5B1 refiner. Hipothesis of the examination is based on the assumption that targeted processing of melts can influence the sequence of solidification, development of microstructural characteristics and finally the acquired mechanical properties of the alloy
Properties, production and application of white cast irons
No full textBijeli željezni ljevovi sadrže visok volumni udio karbida u mikrostrukturi zbog čega imaju visoku tvrdoću. Prvenstveno se upotrebljavaju za odljevke koji moraju biti otporni na abraziju. Osim toga, mogu se koristiti i za odljevke od kojih se zahtijeva otpornost na koroziju ili visoke temperature.
U ovom preglednom radu prikazane su vrste, svojstva, utjecaj kemijskog sastava na mikrostrukturu, proizvodnja, toplinska obrada i primjena bijelih željeznih ljevova s perlitnom metalnom osnovom, bijelih željeznih ljevova legiranih niklom i kromom te bijelih željeznih ljevova visokolegiranih kromom.White cast irons have high hardness because they contain a high volume fraction of carbides in the microstructure. They are primarily used for castings that must be resistant to abrasion. In addition, they can also be used for castings that must be resistant to corrosion or high temperatures.
This review article shows the types, properties, the influence of the chemical composition on microstructure, production, heat treatment, and application of pearlitic white cast irons, nickel-chromium white cast irons and high-chromium white cast iron
Application of ion exchange in water preparatio
Get PDFVoda je jedna od najvažnijih tvari u prirodi. Koristi se za ljudsku potrošnju, ali i za različite potrebe u industriji. Sukladno zahtjevima potrošača voda mora biti adekvatno pročišćena odnosno pripremljena. Za tu namjenu koriste se različite metode poput adsorpcije, membranske filtracije, reverzne osmoze i slično. Kao najefikasnija, najjednostavnija i ekonomski najisplativija metoda za pripremu vode pokazala se ionska izmjena. U ovom radu su kroz teorijski pregled obrađeni osnovni pojmovi vezani uz ionsku izmjenu. Prikazana je najosnovnija primjena ionskih izmjenjivača u tehnologiji vode, odnosno pri dekarbonizaciji, omekšavanju, demineralizaciji i denitrifikaciji vode. Osim toga, prikazani su osnovni načini regeneracije zasićenih ionskih izmjenjivača.Water is one of the most important substances in nature. It is used for human consumption, but also for different needs in the industry. In accordance with the requirements of consumers, the water must be adequately purified or prepared. For this purpose are used different methods such as adsorption, membrane filtration, reverse osmosis and the like. Ion exchange has proved to be the most efficient, simplest and economically most cost-effective method for water preparation. In this final thesis through the theoretical review basic terms related to ion exchange have been elaborated. The most basic application of ion exchangers in water technology, i.e. decarbonisation, softening, demineralisation and denitrification of water is shown. In addition, basic methods of regeneration of saturated ion exchangers are shown
Numerical study on characteristics of combustion and pollutant formation in a reheating furnace
Get PDFEnergy consumption of fuel-fired industrial furnace accounts for about 23% of the national total energy consumption every year in China. Meanwhile, the reduction of combustion-generated pollutants in furnace has become very important due to the stringent environment laws and policy introduced in the recent years. It is therefore a great challenge for the researchers to simultaneously enhance the fuel efficiency of the furnace while controlling the pollution emission. In this study, a transient three- dimensional mathematical combustion model coupled with heat transfer and pollution formation model of a walking-beam-type reheating furnace has been developed to simulate the essential combustion, and pollution distribution in the furnace. Based on this model, considering nitrogen oxides formation mechanism, sensitivity study has been carried out to investigate the influence of fuel flow rate, air-fuel ratio on the resultant concentration of nitrogen oxides in the flue gas. The results of present study provide valuable information for improving the thermal efficiency and pollutant control of reheating furnace
Effect of combined hole configuration on film cooling with and without mist injection
Get PDFTurbine blades operate under a harsh environmental condition, and the inlet temperature of gas turbines is increasing with requirement of high engine efficiency. Some cooling schemes are adopted to prevent these blades from the thermal erosion of the hot mainstream. Film cooling technology is used widely and effectively in gas turbines. The coolant air is suppressed to the wall by the mainstream after jetting out of the film hole. A new hole configuration is first proposed to improve the film cooling characteristics in this paper. Comparison between a conventional cylindrical hole and a new combined hole is conducted by computational fluid dynamics, and effects of various blowing ratios and droplet sizes are also investigated. Results show that the combined hole configuration provides a wider coverage than that in the cylindrical hole configuration case at high blowing ratios (M = 1.0 and M = 1.5). In addition, the film cooling with mist injection also provides a significant enhancement on cooling performance especially for the combined hole case with a small droplet size (10−5 m)
Analysis of the low energy layering fracture in Al- 2.5Mg-0.7Li alloy
Get PDFThe mechanism of nucleation and propagation of low energy layering fracture, observed during thermo-mechanical testing of Al-2.5Mg-0.7Li alloy in as cast condition, was analyzed. Since the low energy layering fracture is affected by Li segregations and microstructural constituents’ development, solidification sequence of Al-2.5Mg- 0.7Li alloy was investigated in equilibrium and non-equilibrium conditions. Results of the investigations have shown that Mg has more pronounced effect on low energy layering fracture due to reducing solubility of Li in liquid phase and αAl, maximizing precipitation of hardening (Al3Li) δ’ phase, ternary (Al2LiMg) T phase and (Al8Mg5) β phase, and reducing ductility by solid solution hardening
Influence of solution hardening on microstructure and mechanical properties of Al-2.5Mg-0.7Li alloy
Get PDFAlthough utilization of lightweight aluminum alloys in transportation industry reduced harmful emissions and improves fuel economy, their further application is limited by low stiffness, low Young modulus and sensitivity to elevated temperatures. It was found that specific strength properties of aluminum alloys can be improved by Li additions. The beneficial effect is achieved by precipitation of hardening Al3Li precipitate. The microstructural and mechanical properties of Al-2.5 Mg-0.7 Li alloy were investigated in as cast and solution hardened condition. The microstructure constituents and thermo-mechanical properties for both conditions were determined and compared
Effect of antimony on austenite transformation and the metallic matrix structure in different wall thicknesses of ductile iron castings
No full textEffects of additions of 0.0039, 0.01, 0.019 and 0.029 wt.% Sb on austenite transformation and the metallic matrix structure in the wall thicknesses of 3, 12, 25, 38, 50, 75 and 100 mm of ductile iron casting containing 2.11 wt.% Si and a low amount of Cu, Sn and Mn were analyzed in this paper. In the examined ductile iron casting without the addition of Sb, the share of pearlite in the metal matrix was decreased and the share of ferrite was increased with increasing wall thickness. The share of pearlite was low. Additions of Sb were increased the share of pearlite in all the walls. Increase of Sb content resulted in increasing the share of pearlite. Almost the same high share of pearlite in the wall thicknesses of 12, 25, 38, 50, 75 and 100 mm was obtained by addition of 0.029 wt. % Sb (varied from 96.00 to 97.61 %). The additions of 0.01, 0.019 and 0.029 wt.% Sb were resulted in a fully pearlitic metallic matrix in the wall thickness of 3 mm. Iron carbides were found in the wall thickness of 3 mm when Sb was added
Properties of continuously casted Cu-Al alloy
Get PDFIn this work are shown properties of continuously casted Cu – 9.1Al alloy before and after heat treatment. The continuously cast cylindrical bar with 8 mm diameter was produced using the device for the vertical continuous casting which is connected with the vacuum induction furnace. Heat treatment was consisted of annealing at 900 °C/30 minutes and water quenching. Microstructural analysis was performed by optical microscopy (OM), scanning electron microscopy (SEM) equipped by device for energy dispersive spectroscopy (EDS) and using differential scanning calorimeter (DSC). Also, hardness and mechanical properties were measured. EDS analysis confirmed that as-cast state of Cu – 9.1Al alloy is successfully done and alloy with homogeneous composition was produced. Optical and scanning electron microscopy showed existence of dual-phase α+β microstructure, which keeps after heat treatment but with certain sporadic changes of α - phase shape. DSC analysis on all samples presented one endothermic change of the heat flow during the heating, which probably represents α→β transformation and one exothermic change of the heat flow during the cooling which probably represents β→α transformation. The effect of heat treatment on the hardness and yield strength values is insignificant, while the tensile strength decreases with annealing
Microstructural analysis of Cu-Al-Mn-(Ti) ribbons with shape memory effect
Get PDFU ovom radu provedena je mikrostrukturna analiza Cu-Al-Mn i Cu-Al-Mn-Ti legure s prisjetljivosti oblika. Ispitivanje se provodilo na uzorcima u lijevanom i kaljenom stanju. Istraživane legure su proizvedene “melt spinning“ postupkom. Nakon lijevanja provedena je toplinska obrada dobivenih traka. Toplinska obrada se sastojala od žarenja na 900 ℃ u trajanju 30 min te hlađenja u vodi. Mikrostrukturna analiza je provedena optičkom mikroskopijom (OM), pretražnom elektronskom mikroskopijom (SEM) te energetsko disperzijskom spektrometrijom (SEM). Temperature faznih transformacija određivane su pomoću diferencijalno pretražne kalorimetrije dok je fazni sastav određen pomoću rendgenske difrakcijske analize (XRD). Utvrđeno je da se mikrostruktura lijevane Cu-Al-Mn legure sastoji od β_1 faze i martenzita β_1^, dok se Cu-Al-Mn-Ti legura u lijevanom stanju sastoji od dvofazne α+β mikrostrukture. Toplinskom obradom postignuta je martenzitna mikrostruktura kod obje istraživane legure. DSC analizom su utvrđene temperature faznih transformacija.In this work the microstructural analysis has been performed on Cu-Al-Mn and Cu-Al-Mn-Ti alloy with shape memory effect. The testing was performed on the samples in casting and quenched state. The investigated alloys were produced by a “melt spinnig“ process. After casting, the heat treatment of the obtained ribbons was performed. Heat treatment consisted of annealing at 900 ℃ for 30 minutes and cooling in water. Microstructural analysis was performed by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectrometry (SEM). Temperatures of phase transformation were determinated by differential scanning calorimetry while the phase composition was determined by X-ray diffraction analysis (XRD). It has been found that the microstructure of as-cast Cu-Al-Mn alloy consists of β_1 phase and martensite β_1^, while Cu-Al-Mn-Ti alloy in as-cast state consists of two phase α+β microstructure. Heat treatment resulted in a martensitic microstructure in both investigated alloys. Phase temperature were determined by DSC analysis