Preparation of Ti–Ni–Fe phase by levitation and its structural characterisation A. Sypien* and W. Przybylo This paper presents results concerning the electromagnetic levitation of solid metal samples. It describes the levitation system and some coils designed to melt 10 g metal samples under controlled atmosphere, as well as melting the process. The main advantage of the method is the absence of any type of crucible and owing to this, the effect of side reaction can be avoided, resulting from the influence of the active metal on the walls of the ceramic crucible in the physicochemical investigations. In many cases, the side reaction makes the correct interpretation of the experimental results sometimes difficult and/or impossible. In order to describe the crystallisation process and the change in the microstructure of the samples obtained during electromagnetic melting at the intermetallic Fe–Ni–Ti phase, a scanning electron microscopy analysis and an X-ray diffraction analysis were used. Keywords: Levitation melting, Intermetallic compound Introduction The increasing need for science and technology for new materials possessing better mechanical, semiconductive or optical properties makes the process of crystallisation of great interest. The latter is the most important factor influencing the utilitarian properties of materials obtained by the process of casting, as it determines the type, number and distribution of phases, as well as their geometric characteristics; in other words, it forms the structure of the cast, which directly affects its proper- ties. 1 That is why this investigation is devoted to melting by means of electromagnetic levitation. The method, due to the process of rapid crystallisation during the casting, makes it possible to obtain casts of a dispersed structure and the elimination of the effect of segregation. Generally speaking, the process of rapid crystal- lisation means the use of high speed cooling or high undercooling, in order to obtain a high speed shift of the crystallisation front (u.1 cm s 21 ). The type of the process, the cooling speed and the type of the material determine the type of nucleation and the growth of the solid phase. In the material, a number of metastable phases can form, which have structures of different types, dendrites and eutectics. 2 Thus, the knowledge of the metastable phase equilibrium diagram makes it possible to predict the microstructure to be formed. The process of rapid crystallisation enables to obtain materials with better properties which are improved due to dispersion of the dendrite or eutectic structure, reduction or elimination of the effect of segregation, formation of the solid phases of extended solubility of the component or the metastable phases, and change of the phase morphology. 3 The aim of the investigation was to use the process of melting by means of the electromag- netic levitation method, in order to obtain monophase alloys and eliminate the effect of segregation. Experimental The following alloys were used as the experimental material: Ti 50 Fe 15 Ni 35 (alloy 1), Ti 50 Fe 25 Ni 25 (alloy 2) and Ti 50 Fe 35 Ni 15 (alloy 3). The alloys were obtained in a furnace used for metal melting by means of the electromagnetic levitation method, with the application of an ‘inner’ heating coil, placed inside the chamber of the furnace. The furnace for levitation melting was designed and produced, showing the basic positive properties of the crucible free electromagnetic levitation melting: lack of a ceramic crucible, a possible source of impurities in the reactive alloy (titanium); intensive mixing and quick homogenisation of the liquid alloy; possibility of obtaining very high temperatures in a short period of time, on the other hand, a possibility of applying techniques for a quick metal freezing. The furnace consists of a frame with flanges, made of stainless steel, in a form of a cylinder with a vertical axis, and two sleeves, one of which is designed to fasten the seal wire and the other is designed to observe the metal when placing it in the heating coil and during melting (Fig. 1). The cover of the furnace contains two extra viewing windows and the vacuum manometer used to measure the pressure of the gas in the furnace. The heating inductor constitutes the horizontal coils of the copper tube: in the bottom part, the coils are placed conically; in the upper part, the coils are placed cylindrically, and both parts of the inductor’s winding are coiled in opposite directions to one another (Fig. 2). Institute of Metallurgy and Materials Science of the Polish Academy of Sciences, 25 Reymonta St., 30-059 Krako ´ w, Poland *Corresponding author, email nmsypien@imim-pan.krakow.pl ß 2010 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 15 November 2008; accepted 11 February 2009 DOI 10.1179/174328409X422257 Materials Science and Technology 2010 VOL 26 NO 1 31