Structure of alloys and equilibrium phase diagram of the Zr-Ru-Ir system. VI. Influence of iridium on the stability of the laves phase ZrRu2
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Information is given regarding the metallic systems investigated by V. N. Eremenko and his school over the decades 1960-1990. His. approach to predicting the phase equilibrium diagrams and thermodynamic properties of unknown systems, based on the generalization of experimental data obtained in this period, is discussed. The prediction level (methods of successive comparison, interpolation or extrapolation, correlation, thermodynamic modeling) depends not only on the amount and reliability of data generalized, but also on the thermodynamic properties of the systems under consideration. The necessity of using a combined approach, in which experimental and calculated phase diagram and thermodynamic data are used together, is emphasized. Mathematical optimization and evaluation of such data made it possible to obtain information on the thermodynamics and phase diagrams of previously unknown systems, and to establish a methodological base for predicting the phase diagrams of multicomponent systems of any degree of complexity.V. N. Eremenko assigned primary significance to the investigation of phase equilibria, construction of phase equilibrium diagrams for condensed systems, and study of the thermodynamic properties of alloys and compounds as the most important components of contemporary materials science. His investigations in these fields were initiated in the late 1940's, early 1950's [1,2] in the Institute for Ferrous Metallurgy of the Academy of Sciences of the Ukr. SSR and in the Kiev State University. They have been extended and continue to the present time in the school established by V. N. Eremenko at the Institute for Materials Science Problems of the Ukrainian Academy of Sciences.Phase equilibrium diagrams (PED) contain in themselves, and present in a concise graphical form, the most important information on the fundamental properties of simple and complex substances. As geometrical reflections of the relative thermodynamic stability of phases, they are reflections of the chemical interactions of the components --of the nature and strength of chemical bonds in the phases which coexist in equilibrium. As geometrical representations of the dependence of alloy phase composition and structure (and, thus, of the types of phase transformations) on equilibrium conditions, they are basic information for those who develop new materials, and also for chemists and physicists investigating the properties of substances. Experimental studies of structure, phase stability and phase equilibria; theoretical investigations of the nature and strength of chemical bonds; thermodynamic calculation of phase equilibria; and, fmaUy, critical evaluation and compilation of data on alloy thermodynamics and phase diagrams constitute, in a sense, a unified field of knowledge on the structure of alloys in the state of thermodynamic equilibrium (Fig. 1).All of the enumerated subjects are successfully pursued in Ukraine. V. N. Eremenko made a large contribution to the establishment and development of this field of materials science in the...
Information is given regarding the metallic systems investigated by V. N. Eremenko and his school over the decades 1960-1990. His. approach to predicting the phase equilibrium diagrams and thermodynamic properties of unknown systems, based on the generalization of experimental data obtained in this period, is discussed. The prediction level (methods of successive comparison, interpolation or extrapolation, correlation, thermodynamic modeling) depends not only on the amount and reliability of data generalized, but also on the thermodynamic properties of the systems under consideration. The necessity of using a combined approach, in which experimental and calculated phase diagram and thermodynamic data are used together, is emphasized. Mathematical optimization and evaluation of such data made it possible to obtain information on the thermodynamics and phase diagrams of previously unknown systems, and to establish a methodological base for predicting the phase diagrams of multicomponent systems of any degree of complexity.V. N. Eremenko assigned primary significance to the investigation of phase equilibria, construction of phase equilibrium diagrams for condensed systems, and study of the thermodynamic properties of alloys and compounds as the most important components of contemporary materials science. His investigations in these fields were initiated in the late 1940's, early 1950's [1,2] in the Institute for Ferrous Metallurgy of the Academy of Sciences of the Ukr. SSR and in the Kiev State University. They have been extended and continue to the present time in the school established by V. N. Eremenko at the Institute for Materials Science Problems of the Ukrainian Academy of Sciences.Phase equilibrium diagrams (PED) contain in themselves, and present in a concise graphical form, the most important information on the fundamental properties of simple and complex substances. As geometrical reflections of the relative thermodynamic stability of phases, they are reflections of the chemical interactions of the components --of the nature and strength of chemical bonds in the phases which coexist in equilibrium. As geometrical representations of the dependence of alloy phase composition and structure (and, thus, of the types of phase transformations) on equilibrium conditions, they are basic information for those who develop new materials, and also for chemists and physicists investigating the properties of substances. Experimental studies of structure, phase stability and phase equilibria; theoretical investigations of the nature and strength of chemical bonds; thermodynamic calculation of phase equilibria; and, fmaUy, critical evaluation and compilation of data on alloy thermodynamics and phase diagrams constitute, in a sense, a unified field of knowledge on the structure of alloys in the state of thermodynamic equilibrium (Fig. 1).All of the enumerated subjects are successfully pursued in Ukraine. V. N. Eremenko made a large contribution to the establishment and development of this field of materials science in the...
An analysis of the extensive information on the interaction of transition metals of group IV with high-melting platinum metals in binary [1][2][3][4][5][6][7][8][9][10][11] and ternary [12][13][14][15][16][17][18][19][20][21][22][23][24][25] systems accumulated at the Institute of Materials Science of the Academy of Sciences of Ukraine by V. N. Eremenko's school and also data of Western authors [26][27][28] showed that the platinum metals as well as titanium, zirconium, hafnium, which are in the same group of the periodic table, are metallochemically not complete analogs. For instance, upon transition from ruthenium to osmium, rhodium, and, in particular, iridium, the number of compounds forming in binary systems greatly increases. The replacement of titanium by zirconium leads, on the one hand, to an increase of the number of compounds, on the other hand to the appearance of a different crystal structure in compounds with the same stoichiometry ( Fig. 1, Table 1). Yet neither the dimensional factor nor the factor of electron concentration expressed in terms of the sum of (s + d)-electrons per atom is completely determining.Nevertheless a number of regularities were discovered in the structure of the phase diagrams of binary systems formed by transitions metals of group IV and high-melting platinum metals. In all the systems phases with the equiatomic composition AB form. It can be seen from Fig. 1 that they all (except ZrOs) melt congruently and are high-melting compounds. Their melting point is sometimes as high as 2600°C. Such high thermal stability is well correlated with the published data on the high thermodynamic stability of these phases [29, 30]. The crystal lattice of the high-temperature modification of the mentioned phases belongs to the structural type CsCI. In systems with ruthenium and osmium it is stable down to room temperature, in systems with rhodium and iridium a lowering of the temperature entails polymorphic transformation in consequence of the lattice being distorted into a tetragonal one and then into a more complex one, viz., a monoclinic or rhombic one. In all systems with rhodium and iridium there forms a phase with composition AB 3 and with a crystal lattice of type AuCuy A characteristic trait of the phase diagrams under consideration is that there is no trace at all of Laves phases in systems with titanium whereas in systems with zirconium all the platinoids except rhodium form a Laves phase, and in systems with hafnium only osmium does, although the criteria of the formation of Laves phases (the dimensional factor ~md the electron concentration) are favorable in all the systems under consideration. Consequently the mentioned criteria are, as repeatedly pointed out a necessary but not a sufficient condition of the formation of Laves phases.In the range of compositions rich in a transition metal of group IV the number of intermediate phases increases in the series Ti ---Hf--, Zr. In the series of platinoids their number increases from osmium to rhodium and then to iridium; ruthenium, ...
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