|Kazimierz Głownia, Andrzej Gwiżdż, Zenon Pirowski, Jacek Wodnicki|
The role of interstitial elements, i.e. nitrogen and boron, in the process of ductile iron solidification and heat treatment of castings was discussed. Austempering of ductile iron aims at obtaining an ausferritic matrix structure. Austempering is the kind of heat treatment that consists in cooling the alloy from the austenitising temperature, first, followed by further cooling in a salt bath at a constant temperature. The initial research studies proved favourable effect of boron microadditions on an increased rate of the ductile iron isothermal transformation process. The following cast iron grades were made: basic composition (designation 1/ADI), cast iron with an addition of nitrogen (designations 2/N1 and 4/N2), cast iron with an addition of boron (designations 3/B1 and 5/B2), and cast iron with additions of nitrogen and boron (designation 6/N B). The cast alloys were subjected to thermal analysis, their structure was examined, and hardness measurements were taken. The specimens cut out from ingots cast from the above mentioned alloys were subjected to heat treatment. Two austempering variants were applied, i.e. at temperatures of 275ºC and 350ºC. Mechanical tests were carried out (Rm, A5, KV, HB) and microstructure was examined after both heat treatment variants. The analysis of the obtained results enabled determination of the effect of boron and nitrogen microadditions on the as-cast and austempered structure of the examined iron; the effect on selected mechanical properties was established as well.
Keywords: ductile iron, austempering, structure, cast iron properties,
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Andrzej Białobrzeski, Marzena Lech-Grega, Janusz Żelechowski
The study presents the results of examinations carried out on ultra-light magnesium- and lithiumbased alloys of two-phase α-β structure and monophase β structure using scanning electron microscopy with chemical analysis in microregions (SEM + EDX - Philips XL30 + EDAX) and X-ray phase analysis (XRD - X-ray diffractometer model D8 Advance, Bruker). The diffraction reflexes were interpreted from a PDF-2 catalogue. It was observed that the addition of alloying elements (calcium or aluminium) definitely changes the structure of monophase Mg-Li α or β alloys. Calcium addition to a cast binary Mg-Li-Ca alloy results in the formation of two-phase structure composed of β phase dendrites, lamellar CaMg2 eutectic, and probably α phase. The addition of aluminium to a cast binary alloy from the Mg-Li-Al system results in the formation of a two-phase α and β system. The Mg-18,4%Li-1,2%Zn alloy is a monophase β structure material with zinc dissolved in alloy matrix.
Keywords: ultralight magnesium and lithium alloys, structural examinations, scanning microscopy, X-ray diffractometer,
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Tomasz Reguła, Paweł Darłak, Adam Tchórz, Marzena Lech-Grega
The study describes the attempts to use a mechanochemical synthesis in the fabrication of composites based on Cu-Al intermetallic compounds reinforced with homogeneously distributed ceramic Al2O3 phase. For this purpose, a high-energy ball mill was used to obtain the reaction of malachite reduction Cu2(OH)2CO3 with powdered aluminium Al0. The aim was to produce, besides the (Al2O3) ceramic phase, intermetallic CuxAly phases. Thus obtained materials were subjected to examinations by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). It has been proved that it is possible to fabricate a composite based on the intermetallic Cu9Al4 compound reinforced with Al2O3, as a result of numerous chemical reactions induced by various stimuli of strictly mechanical nature
Keywords: metal-ceramic composites, mechanosynthesis, ball mill, intermetallic compounds, X-ray diffraction,
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Aleksandra Siewiorek, Natalia Sobczak, Artur Kudyba
The wettability tests were carried out under a vacuum at 700°C in the drop/substrate couples, where drop is pure aluminium (99.999%), substrate - Ni (99.8%) and Niox (oxidized). Test were carried out using two different testing procedures: classical sessile drop method coupled with contact heating of the same Al/Ni couple (CH) and capillary purification method, where primary oxide film is removed from the surface of liquid aluminum (CP). After wettability tests, cross - sections of the samples were observed using optical microscope and SEM in order to observe phase boundaries of Al/Ni and Al/Niox couples and its phase morphology. The presence of characteristic phases of rhombic Al3Ni and irregular phase Al3Ni2 were observed. Tests of shear strength (push-off shear tests) and microhardness measurements of the phases were also performed. It was found that arose after contact with aluminum products of the reaction zone (RPR) on the oxidized nickel substrate is thinner than on the substrates unoxidized. Couple Al/Ni with a thin and compact RPR (reaction product region) resulting from the influence of Ni with a drop in the method of CH obtained after settling of the Al drop by CH in the oxidized nickel substrate is also the most resistant to shearing of the tested systems. The value of shear stress in this case is 63.1 MPa, and for the system Al on unoxidized nickel substrate obtained by the CP is only 33.9 MPa.
Keywords: aluminium-nickel system, wettability, microstructure,
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