Preparation and evaluation of properties of cast metallic foams with regular inner structure

Lately we encounter still more new applications of metallic foams, as well as possible methods of their manufacture. These metallic materials have specific properties, such as large rigidity at low density, in some cases high thermal conductivity, capability to absorb energy, etc. The work is focused on the preparation of these materials using conventional casting technology, which ensures rapid and economically feasible method for production of shaped components. In the experimental part we studied conditions of casting of metallic foams with a regular structure made of ferrous and non-ferrous alloys. For thus obtained castings we evaluated the achieved microstructure and mechanical properties, which determine the possible use of these materials. The samples were subjected to compression tests, by which we investigated deformation behaviour of selected materials and determined the value of energy absorption.Web of Science6231646164

Manufacturing of cast metal foams with irregular cell structure

Metallic foams are materials of which the research is still on-going, with the broad applicability in many different areas (e.g. automotive industry, building industry, medicine, etc.). These metallic materials have specific properties, such as large rigidity at low density, high thermal conductivity, capability to absorb energy, etc. The work is focused on the preparation of these materials using conventional casting technology (infiltration method), which ensures rapid and economically feasible method for production of shaped components. In the experimental part we studied conditions of casting of metallic foams with open pores and irregular cell structure made of ferrous and nonferrous alloys by use of various types of filler material (precursors).Web of Science152585

Evaluation of properties of cast metal foams with irregular inner structure

Internal structure of metal foams is one of the most important factors that determine its mechanical properties. There exists a number of methods for studying the nature of the inner porous structure. Unfortunately most of these processes is destructive and therefore it is not possible to reuse the sample. From this point of view, as a suitable method seems to be the ability of using the so-called X-ray microtomography (also micro-CT). This is a non-destructive methodology used in a number of fields (industry, science, archaeology, medicine) for a description of the material distribution in the space (e.g. pores, fillers, defects, etc.). In principle, this technology works on different absorption of X-ray radiation by materials with changing proton number. The contribution was worked out in collaboration with experts from the Faculty of Electrical Engineering and Computer Science of the VSB-Technical University of Ostrava and it is focused on the analysis of internal structure of the metal foam casting with irregular arrangement of internal pores by using micro-CT. The obtained data were evaluated in the commercial software VGStudio MAX 2.2 and in the FOTOMNG system. For the evaluation of these data a new specialized module was introduced in this system. Several methods of pre-processing the image was prepared for the measurement. This preliminary processing consists, for example, from a binary image thresholding for better diversity between the internal porosity and the material itself or functions for colour inversion.Web of Science6341851184

Proposal of method of removal of mould material from the fine structure of metallic foams used as filters

Metallic foams are materials that are subject of an ongoing research with the broad applicability in many different areas (e.g. automotive industry, building industry, medicine, etc.). These metal materials contain in their structure artificially created pores. These pores give them specific properties, such as: large rigidity at low density, high thermal conductivity, capability to absorb energy, etc. Since the discovery of porous metallic materials numerous methods of production have been developed. The aim of the paper is to introduce effective casting methods of manufacturing of metallic foams, namely cast metal filters from the aluminum alloy. Research deals with investment casting with use of pattern made of polymeric foam, which is used for production of metallic foam with open pores. The main disadvantage of this procedure consists in removing the mould material without damaging the fine structure of the cast filter. Plaster is used as the mould material and the most important result of this paper is the presentation of the effective procedure of plaster removal from the porous structure of cast filters.Piany metalowe są przedmiotem wielu badań gdyż znajdują szerokie zastosowanie w wielu dziedzinach np. produkcji samochodów. budownictwie czy w medycynie. W swojej strukturze zawierają sztucznie wytworzone pory, zapewniające uzyskanie specyficznych właściwości jak duża wytrzymałość, niewielka gęstość, wysokie przewodnictwo cieplne zdolność do absorpcji energii itp. Od czasu wynalezienia porowatych materiałów metalowych opracowano wiele metod ich wytwarzania. Celem opracowania jest wprowadzenie efektywnych metod odlewniczych produkcji pian metalowych, szczególnie ze stopów glinu. Studium zajmuje się precyzyjną metodą odlewania przy zastosowaniu modelu wykonanego z piany polimerowej stosowanej w produkcji piany z otwartymi porami. Główna niedogodność metody polega na trudności usuwania materiału formierskiego, bez naruszenia delikatnej struktury odlewanego filtra. Jako materiał formierski stosuje się gips i najważniejszym wynikiem pracy jest przedstawienie efektywnej procedury usuwania gipsu z porowatej struktury odlanego filtra.Web of Science59273072

Influencing of foundry bentonite mixtures by binder activation

Although new moulding processes for manufacture of high quality castings have been developed and introduced into foundry practice in recent years, the green-sand moulding in bentonite mixture still remains the most widely used technology. Higher utility properties of bentonite binders are achieved through their activation. This contribution is aimed at finding a suitable activating agent. A number of sodium salts and MgO based agents has been chosen. In the framework of the experiment the swelling volume of chosen agents was tested and technological parameters of a bentonite mixture with a binder activated with the studied agents were determined.Web of Science55110

Thermophysical properties and microstructure of magnesium alloys of the Mg-Al type

Generally speaking, magnesium alloys of the Mg-Al type are used as structural materials, but their disadvantage lies in their low heat resistance. The addition of suitable alloying elements can be positive, as it makes it possible to achieve good thermo-mechanical properties. For the application of a specific material for thermally stressed cast parts it is necessary to consider the extent of their linear and volumetric changes at elevated and high temperatures. The aim of this paper is to study the behaviour of selected magnesium alloys based on Mg-Al during heat stress conditions in order to simulate real conditions using dilatometric analyses. These properties were evaluated on samples of alloys prepared by gravity casting in metallic moulds. The effect of the metallurgical processing of the alloys on the studied parameters was also investigated.Web of Science49581180

Uporaba prekurzorjev za izdelavo litih kovinskih pen

The presented work was devoted to the development of the production processes for metallic foams, which were based on conventional casting technologies. The use of the standard casting processes and standard materials made it possible to identify the range of metallic foams amongst affordable materials, thereby making a full use of their application potentials. The experimental part was focused on the development and subsequent optimization of the casting processes for manufacturing cast metallic foams with irregular inner-cell structures, and especially on the development of the technology of infiltrating molten metal into a mold cavity filled with precursors.Avtorji predstavljajo razvoj procesa izdelave kovinskih pen, ki temelji na konvencionalnih tehnologijah litja. Zaradi uporabe standardne livarske prakse in materialov spadajo kovinske pene med dostopne materiale, in tako je mogoč poln izkoristek njihovega potenciala. Eksperimentalni del študije je bil osredotočen na razvoj in takojšnjo optimizacijo livarskega postopka izdelave kovinskih pen z nepravilno notranjo celično strukturo. Delo je bilo še posebej osredotočeno na razvoj tehnologije infiltracije kovinske taline v votlino orodja, ki je bila pred tem napolnjena s predhodno surovino (prekurzorjem).Web of Science53219118

Uporaba vodotopnih dodatkov v proizvodnji litih kovinskih pen

The paper is devoted to the field of manufacturing cast metallic foams - porous metal materials - with a stochastic arrangement of the inner cavities. The mastering of inexpensive ways of manufacturing metallic foams is a prerequisite for a full utilization of such a material. That is why the experimental part was devoted to the casting technologies for the production of metal foams based on conventional foundry processes. In the experiment, the infiltration of molten metal into mould cavities filled with precursors was tested. Particular attention was paid to the use of water-soluble precursor materials. It is assumed that a thorough knowledge of the production parameters and conditions will contribute to the expansion of the foundry range, which can also increase the competitiveness of this industry on a global scale.Pričujoči članek opisuje izdelavo litih kovinskih pen, to je poroznih kovinskih materialov s stohastično (naključno) porazdelitvijo notranjih praznin oz. por. Umetnost obvladovanja cenenih poti proizvodnje kovinskih pen je temelj za izkoriščanje uporabnosti tega materiala. Avtorji članka so se v eksperimentalnem delu tako posvetili tehnologijam litja v proizvodnji kovinskih pen, ki temeljijo na konvencionalnih livarskih postopkih. S praktičnim preizkusom so testirali potek infiltracije raztaljene kovine v votlino modela, polnjeno s prekurzorji – izhodnimi dodatki. Posebno pozornost so posvetili vodotopnim prekurzorjem. Zaklju~ujejo z ugotovitvijo, da poznavanje parametrov proizvodnje in pogojev te vrste proizvodnje, prispeva k raz{iritvi livarskega programa, kar lahko tudi pove~a njihovo konkuren~nost na globalnem trgu.Web of Science54112712

Evaluation of the effect of external conditions during crystallization and solidification on the final structure of AlSi7Mg

The paper deals with the possibilities of influencing the final microstructure of aluminium alloy castings by changing the external conditions of crystallization and solidification. Aluminum alloys, especially Al-Si alloys, are nowadays one of the most used non-ferrous metal alloys, especially due to their mass application in the automotive field. It is in this industry that extreme emphasis is placed on the quality of cast parts with regard to safety. For this reason, a key production parameter is the mastery of the control of the resulting microstructure of the castings and the associated internal quality, which is subject to high demands defined by international standards. The aim of the experiment of this paper is to evaluate the effect of different preheating of the metal mould on the resulting structure and hardness of test castings made of AlSi7Mg0.3 material. The hardness measurement will be evaluated on a hardness tester. The parameter SDAS, Microporosity, Content of excluded eutectic will be evaluated. Dependencies will be found and plotted.Web of Scienc

Uporaba grafitnih rotorjev za refinacijo talin iz zlitin na osnovi aluminija

The presented paper is focused on the study of refining aluminium-alloy melts. The quality of castings is determined by the basic material, i.e., the input material (furnace charge), its subsequent melting and subsequent metallurgical modifications. To allow the profitability of production, low-quality input materials are currently used, which, although they have the required chemical composition, may contain a large amount of impurities, coming not only from the original input materials, but also from their processing. To allow a cost reduction, in addition to rejected castings, the residues of gating and chipping from the machining are used as charge materials in foundries. However, the melt thus prepared is heavily contaminated with gases and inclusions.The aim of the research was, therefore, to verify the use of graphite rotors functioning as degassing units for refining aluminium melts. The experiments were conducted under laboratory and pilot-plant conditions using the plant equipment. The refining efficiency was monitored with respect to the type and shape of the graphite rotor and the refining medium used. The achieved purity of the resulting melt was evaluated to establish the density index and the final cast microstructure.Članek opisuje rafinacijo talin iz Al zlitin. Kvaliteta ulitkov je odvisna od osnovnega materiala (sestave, čistosti itd.), postopka taljenja in metalurških modifikacij. S pridobitvenega stališča proizvodnje se trenutno uporabljajo manj kakovostni vhodni materiali, ki sicer ustrezajo glede zahtevane osnovne kemijske sestave, vendar lahko vsebujejo veliko nečistoč. Te se ni nujno, da nahajao v originalnem izhodnem materialu, lahko pa nastajajo tudi med samim proizvodnim procesom. Zaradi zmanjšanja stroškov se v livarnah kot vlo`ek uporabljajo tudi s strani kontrole zavrnjeni ulitki (izmet) in ostanki mehanske obdelave (odrezki, ostružki). Zaradi tega je pripravljena Al talina močno kontaminirana s plini in nekovinskimi vključki. Cilj avtorjev pričujoče raziskave je bil verificirati rafinacijo Al talin z uporabo grafitnih rotorjev v enotah za razplinjevanje. Preizkuse so izvajali na laboratorijskih in pilotnih napravah. Učinkovitost rafinacije so zasledovali glede na tip in obliko izbranega grafitnega rotorja in uporabljeno rafinacijsko sredstvo. Doseženo čistost talin so ovrednotili z določanjem indeksa gostote (naprava Dichte Index) in analizo končne mikrostrukture ulitkov.Web of Science54226526