Papers by Keyword: Light Microscopy

Abstract: The present study describes ice characterization technique by utilizing light microscopy. Two different optical setups were used and compared. For ice structure characterization, ice was formed by adding water to an ice base layer: pouring hot water (+20 °C), pouring cold water (+3 °C) and spraying of hot water (+20 °C) water. Ice substrate specimens were made (20 x 30 x 20 mm prepared in a polypropylene mould) at -20 °C for 48 h. The heat flow direction governed the orientation of the air bubbles, and set the inner structure of ice. Pouring hot water onto ice slowly solidified the top layer and created channel-like pores perpendicular to the top surface, but cold water quickly solidified the top layer and created chaotically oriented air bubbles.

Abstract: The article shows the analysis of castings parts produced by rheocasting method SEED. Structures of as cast and heat treated castings samples were observed by light microscopy and electron microscopy. Scanning electron microscope was also used for studying of fracture surfaces after destruction of the samples during testing of mechanical properties. Also analysis of chemical composition of specific phenomena found within the structure is described. Findings resulting from those analyses are related with the technological settings and other process conditions.

Abstract: . The Ni-base superalloys have an interesting history and evolution since they start to be used in aero jet engines. Microstructures of superalloys have dramatically changed through the years as modern technology of its casting or forging becomes more sophisticated. The first superalloys have polyedric microstructure consist of gamma solid solution, some fraction of gamma prime and of course grain boundaries. As demands on higher performance of aero jet engine increases, the changes in superalloys microstructure become more significant. Further step in microstructure evolution was directionally solidified alloys with columnar gamma prime particles. The latest microstructures are mostly monocrystalline, oriented in [001] direction of FCC gamma matrix. What does not changed through the years is elementary FCC structure of matrix and fundamental group of alloying elements. All microstructure changes bring necessity of proper preparation and evaluation of microstructure. Except already mentioned structures have gamma double prime and various carbides form appear. These structural parameters have mainly positive influence on important mechanical properties of superalloys. However, some detrimental phases as Laves, σ-phase appears as well and have negative influence on heat resistance of superalloys. Paper deals with such microstructural evaluation of both groups of alloys – cast and wrought as well. Microstructure evaluation helps to describe mechanism at various loading and failure of progressive superalloys. Such example where microstructure evaluation is employed is fractography of failure surfaces after fatigue tests, which are as example of metallography evaluation described in this paper as secondary objective. Fatigue test done in this article were at high frequency with push-pull loading, so called high frequency fatigue loading (HFFL) and at low frequency three point flexure, so called low frequency fatigue loading (LFFL).

Abstract: The paper deals with the qualitative, quantitative, and phase analyses of particles that were found during the metallographic analysis of a cracked spring washer made of silicon spring steel 38Si7, with the aim of ruling out the client’s suspicion of possible initiation of graphitization in the course of the heat treatment. The problem is solved via metallographic analysis using light microscopy, scanning electron microscopy including EDS microanalysis of the chemical composition and EDS line analysis.

Abstract: The purpose of these researches was to determine the effect of silicon carbide particles (SiCp) proportion and the effect of some process parameters (temperatures and times of aging) on characteristics of Al-Cu/SiCp composites obtained by P/M route. The age-hardened composites and un-reinforced alloys solution treated at 515 ± 5°C, maintaining time 360 minutes, quenched in water and artificial aging at 150-190^o C during respectively 240-720 minutes/ furnace cooled, were tested from hardness and microstructural point of view. The effect of SiCp proportion in matrix during cold compaction was observed on densification curves of all experimental powders mixtures Al-4Cu/ (5, 10, 15 and 20) wt.%SiC. The composites were analyzed using optical and electron microscopy (including ESEM-Enviromental Scanning Electron Microscopy), in terms of shape and size of grains, pores, ceramic particles, second phases and precipitates.

Abstract: The contribution deals with an analysis of thick wear-resistant coatings produced on the surface of cast iron friction bearings by means of twin wire arc spraying or by pouring, with the aim of comparing the two manufacturing technologies. In addition to a detailed analysis of the microstructure and phase composition of the two types of coating, their mechanical and adhesion properties were established (using tensile and shear stress testing methods as well as cyclic thermal shocks).

Abstract: Steel CB2 developed in frame of the COST actions belongs to the most promising steel for production of cast turbine components working at ultra-supercritical steam conditions. VZÚ Plzeň has participated on assessment of original trial melt CB2 as well as on testing of samples coming from one of pilot valves produced of steel CB2 in full scale. Recently VZÚ Plzeň has cooperated with Doosan Škoda Power in development of weld processes of advanced power energy steels including steel CB2. This contribution deals with a comparison of properties of the steel CB2 produced by four various steelmakers from point of view of their microstructure in relation with their mechanical and creep resistant properties. Evaluation is focused on chemical heterogeneity, porosity, content of non-metallic inclusions, in particular on an occurrence of coarse NB, microstructure and substructure using methods of light and electron microscopy.

Abstract: Production of primary Al- alloys belong to heavy source fouling of life environs. Care of environment in industry of aluminium connects with the decreasing consumptions resource as energy, materials, water and soil, with increase recycling and extension life of products. Recycled (secondary) aluminium alloys are made out of Al-scrap and workable Al-garbage by recycling. Applications of these alloys in recent years increase especially in automotive industry (dynamic exposed cast, engine parts, cylinder heads, pistons and so on). Controlling the microstructure of secondary aluminium cast alloy is very important, because these alloy containing more of additions elements, that forming various intermetallic phases in the structure. Improved mechanical properties of secondary alloys are strongly dependent upon the morphologies, type and distribution of the second phases, which are in turn a function of alloy composition and cooling rate. The presence of additional elements as Mg, Mn, Fe or Cu allows many complex intermetallic phases to form, which make characterization non-trivial. A combination of different analytical techniques (light microscopy, scanning electron microscopy (SEM) upon deep etching and energy dispersive X-ray analysis (EDX)) were therefore been used for the various phases identification.

Abstract: In the present paper, the current state of magnesium scrap recycling via melt refinement was reviewed and the difficulties confronted in the developing fluxless techniques were highlighted. Then, the working principle of a fluxless technique newly developed in China was briefly introduced followed by chemical and light microscopy investigation of the processing quality of the recycled ingots in comparison with the commercial ingot produced with predominant flux processing to have a first insight into the difference of the two refining techniques. The results indicate that a stable, continuous and cost effective melt refinement can be achieved with the commercial Mg scraps in-house fluxless recycling system.

Abstract: Hydroxyapatite (HA), widely used as bone graft, can be modified by the incorporation of bivalent cations (Mg2+ and Zn2+) and its gradual release could favor the bone repair. The purpose of this research was to evaluate the effect of the HA and zinc-containing hydroxyapatite (Zn-HA) in the bone repair in rat calvaria in comparison to autogenous bone. Critical size defect in the calvaria was filled with the graft material and the samples were harvested at the 30, 90 and 180 days. The light microcopy observations showed the biocompatibility of the graft materials. In the Zn-HA group the area of neoformed bone was larger than in the HA group, but smaller than in the autograft. A fibrous connective tissue was more evident around HA granules. It could be conclude that the presence of zinc ions in HA crystal accelerated the osteogenesis and increased the area of newly formed bone in relation to HA.