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Molnar A.,University of Miskolc | Janovszky D.,MTA ME Material Science Research Group | Kardos I.,University of Miskolc | Molnar I.,University of Miskolc | Gacsi Z.,University of Miskolc
Journal of Electronic Materials | Year: 2015

Melting and crystallization processes of lead-free and lead-contaminated alloys in near-equilibrium state were investigated. In addition, the effect of silver content up to 4 wt.% on the microstructure of Sn-Ag-Cu alloys was studied. The volume fraction of β-Sn decreased by half owing to 4 wt.% Ag content. Furthermore, contamination by lead strongly influences the properties of the solidified microstructure. The Pb grains appear as a result of two processes when the Pb content is equal to 0.5 wt.% or higher: Pb phase solidifies in the quaternary eutectic at 176°C, and Pb grains precipitate from the primary β-Sn solid solution grain during a solid state reaction. The freezing range enlarges to 51°C due to 2 wt.% Pb content owing to quaternary eutectic. Above 1 wt.% Pb content, the mechanical properties also improve due to grains of quaternary eutectic Pb and precipitated Pb grains with a size <1 μm. © 2015, The Minerals, Metals & Materials Society. Source


Janovszky D.,MTA ME Material Science Research Group | Tomolya K.,MTA ME Material Science Research Group | Sveda M.,MTA ME Material Science Research Group | Sycheva A.,MTA ME Material Science Research Group | Kaptay G.,University of Miskolc
Journal of Alloys and Compounds | Year: 2014

Liquid immiscibility was studied in Cu-Zr-Ag-Y and Cu-Zr-Ag-Ni liquid alloy systems. In case of Y addition the liquid decomposes into an Ag-Y rich liquid (L1) and into a Cu-Zr rich liquid (L2). In case of Ni addition the separated liquid phases are Ag-rich and Cu-Zr-Ni rich liquids. Different microstructures were found as function of the volume fraction of the L1 liquid phase. The Y addition increased the field of miscibility gap of the ternary Cu-Zr-Ag system to a greater extent compared to Ni addition. Also, the rate of coalescence of droplets in the Cu-Zr-Ag-Y system was considerably larger compared to the Cu-Zr-Ag-Ni system. These two observations are interconnected: increased miscibility means more positive excess Gibbs energy, which leads to higher liquid/liquid interfacial energy, being the driving force of coalescence. Alloys with different compositions taken from the tip of the wedge have been studied by DSC. The amorphous fraction progressively reduces when increasing the Ag-content. A small amount of amorphous phase was detected by DSC in the alloy with Ag contents of not greater than 50 at%. © 2014 Elsevier B.V. All rights reserved. Source


Mertinger V.,University of Miskolc | Benke M.,MTA ME Material Science Research Group | Nagy E.,MTA ME Material Science Research Group | Pataki T.,University of Miskolc
Journal of Materials Engineering and Performance | Year: 2014

The variation of thermal characteristics of the ε ↔ γ transformation during thermal cycling and the effect of Cr content was studied in two Fe-Mn-Cr steels through cyclic DSC examinations. It was found that the martensite start temperature decreased and the austenite start temperature increased in the first cycles, then both stabilized after several cycles. The latent heat of the transformations increased first and then also stabilized. The Cr content pushed the ε ↔ γ transformations to lower temperatures, decreased the thermal hysteresis and the latent heat. It is experimentally shown that 6.53 m/m% Cr content increases the stacking fault energy in this alloy. © 2014 ASM International. Source


Janovszky D.,MTA ME Material Science Research Group | Tomolya K.,MTA ME Material Science Research Group
Materials Science Forum | Year: 2014

The Cu-Zr-Ag system is characterized by a miscibility gap. The liquid separates into Agrich and Cu-Zr rich liquids. Yttrium was added to the Cu-Zr-Ag and Cu-Zr-Ag-Al systems and its influence on liquid immiscibility was studied. This alloying element has been chosen to check the effect of the heat of mixing between silver and the given element. In the case of Ag-Y system it is highly negative (-29 kJ/mol). The liquid becomes immiscible in the Cu-Zr-Ag-Y system. To the effect of Y addition the quaternary liquid decomposed into Ag-Y rich and Cu-Zr rich liquids. The Y addition increased the field of miscibility gap. An amorphous/crystalline composite with 6 mm thickness has been successfully produced by liquid-liquid separation based on preliminary calculation of its composition. The matrix was Cu38Zr48Al6Ag8 and the crystalline phases were Ag-Y rich separate spherical droplets. © (2014) Trans Tech Publications, Switzerland. Source

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