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Mertinger V.,University of Miskolc | Benke M.,Materials Science Research Group | Nagy E.,Materials Science Research Group
Materials Today: Proceedings | Year: 2015

The characteristics of the martensitic transformations induced by uniaxial tensile tests performed between room temperature and 200 °C in two Fe-Mn-Cr alloys with different Cr contents were examined. Different volume fraction of α' martensite and ε martensite were detected in the austenitic matrix as the function of parameters of the thermo-mechanical treatments. Quantitative and qualitative phase analyses by X-ray diffraction were carried out on the samples. The crystallographic orientation (texture) of the phases on macro scale was also determined. The decomposition of ε martensite was followed by DSC measurements. It was found that increasing Cr content increased the stability of austenite, thus, increased the stacking fault energy. The increased Cr content also suppressed the formation of α' martensite. Deformation of austenite stabilized the austenite phase and led to the formation of textured ε martensite. © 2015 The Authors.


Roosz A.,University of Miskolc | Kovacs J.,Materials Science Research Group | Ronafoldi A.,Materials Science Research Group | Kovacs A.,University of Miskolc
Materials Science Forum | Year: 2013

Al-7wt.% Si-1wt.% Fe alloy was solidified unidirectionally in the Crystallizer equipped with a High Rotating Magnetic Field (CHRMF) device. The diameter of the sample was 8 mm and its length was 120 mm. The parameters of solidification were as follows: solid/liquid interface velocity ~0.082 mm/s, temperature gradient 7±1 K/mm, no magnetic field or RMF with magnetic induction 150 mT and frequency of magnetic field 50 Hz. The structure obtained after solidification carried out without rotating magnetic field showed the regularly distributed columnar dendrites. However solidification performed under magnetic stirring produces a structure of dual periodicity. On the one hand, the branches of the "Christmas tree"-like structure containing Al+Si binary eutectic was formed. On the other hand, bands with the higher Fe- and Si-contents appeared, which were distributed in a larger distances from each other than the branches of the "Christmas tree" structure. The developed phases were analyzed by SEM with EDS. The average Si- and Feconcentrations were measured along the length of the longitudinal section of the rod. Furthermore, the Si- and the Fe-concentrations within the bands' area as well as the composition of the compounds were determined. © (2013) Trans Tech Publications, Switzerland.


Budenkova O.,Grenoble Institute of Technology | Baltaretu F.,Technical University of Civil Engineering Bucharest | Kovacs J.,Materials Science Research Group | Roosz A.,Materials Science Research Group | And 3 more authors.
IOP Conference Series: Materials Science and Engineering | Year: 2012

We propose an approach for the solidification of metallic alloys taking into account the turbulence in the liquid phase. For modeling of the turbulent flow a k-ε model is used. This model is applied for solidification of AlSi-based alloys under the action of rotating electromagnetic field of intensity up to 65mT. Two cases have been considered, namely solidification of a binary Al-7wt%Si and a ternary alloy Al-7wt%Si-1wt%Fe. It is shown that increase of the electromagnetic field leads to the formations of various types of channels. © Published under licence by IOP Publishing Ltd.


Sveda M.,Materials Science Research Group | Sycheva A.,Materials Science Research Group | Kovacs J.,Materials Science Research Group | Ronafoldi A.,Materials Science Research Group | Roosz A.,Materials Science Research Group
Materials Science Forum | Year: 2014

The peritectic alloys, such as some types of steel, Ni-Al, Fe-Ni, Ti-Al, Cu-Sn, are commercially important. In contrast to other types of alloys, many unique structures (e.g. banded or island ones) can form when peritectic alloys are directionally solidified under various solidification conditions. It can be observed in the course of the directional solidification experiments performed in a rotating magnetic field (RMF) that the melt flow has a significant effect on the solidified structure of Sn-Cd alloys. This effect was investigated experimentally for the case of Sn-1.6 wt% Cd peritectic alloy. For this purpose, a Bridgman-type gradient furnace was equipped with an inductor, which generates a rotating magnetic field in order to induce a flow in the melt. As a result, the forced melt flow substantially changes the solidified cellular microstructure. The cell size and the volume fraction of the primary tin phase were measured by an image analyzer on the longitudinal polished sections along the entire length of the samples. The microstructure was investigated by scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). © (2014) Trans Tech Publications, Switzerland.

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