Fartushna I. Phase equilibria, structure and properties of alloys of titanium and iron systems with d-metals, p-elements and REM. – Qualifying scientific work asсollection of cientific manuscripts.
The Doctor of Science thesis by speciality 02.00.04 – physical chemistry. I.M. Franceviсh Institute for Problems of Material Science, NAS of Ukraine, Kyiv, 2021.
The thesis is devoted to the construction of phase diagrams of ternary systems Ti-{V, Zr, Co, Ni, Ga}-Sn, Zr-Co-Sn, Ti-{V, Cr}-Si, Fe-R-{C, Co, Ni} and some boundary binaries in wide concentration and temperature ranges.
The intermetallic compounds and miscibility gap in liquid phase in the La-Fe system were not confirmed. Most remarkable feature of La-Fe-C system involves isolatedmiscibility gap in liquid phase L1 + L2 and formation of ternary compound La3,67FeC6 (τ) (La3,67FeC6, hP24-P63/m). It is shown that τ is formed by peritectic reaction at 1250 °C. An expert evaluation of the published data on phase equilibria was performed for Fe-Ce-C and Fe-Nd-C systems. The absence of a miscibility gap in liquid phase, in contrast to La-Fe-C system, confirms the conclusion that the shape of liquidus curve of La-Fe system determines the appearance of a miscibility gap in La-Fe-C system.
A new binary compound Ce5Ni19 was found. Its crystal structure was determined (Ce5Co19, hR72-R-3m). Ce5Ni19 is formed by a peritectic reaction at 1123 °C. New ternary compounds Ti5GaSn2 (Nb5SiSn2, tI32-I4/mcm)and Ti2Ni2Sn (U2Pt2Sn, tP20-P42/mnm) were found and their crystal structure was established. The crystal structure of the ternary compound Zr5Co6Sn18 was determined for the first time.The thermodynamic description of the Ti-Ni-Sn system is carried out. The enthalpies of formation of ternary compounds Ti5GaSn2, TiNi2Sn, TiNiSn, Ti2Ni2Sn and Ti5NiSn3 have been calculated. It is shown that ternary compound (Co,Fe)17La2 (τ) (Th2Zn17, R-3m) is formed by peritectic reaction at 978 °C and has a wide homogeneity range from 46 to ~78 % Co at solidus temperature.
It was found that compounds Ce2Fe17 and Ce2Co17 and Laves phases Fe2Ce and Co2Ce continuous solid solutions Ce2(Co,Fe)17 and Ce(Co,Fe)2. The Laves phases Fe2Ce and Ni2Ce also form a continuous solid solution Ce(Ni,Fe)2.
An expert evaluation of the published data on phase equilibria was performed for the Fe-Mn-Ce system. There are two ternary compounds Fe11Mn6Ce2 (τ1) (Th2Ni17, hP38- P63/mmc) and Fe5Mn7Ce (τ2) (ThMn12, tI26-I4/mmm), which are formed by peritectic reactions and have wide homogeneity regions.
A comparative analysis of the studied and related systems was performed. All systems are divided into two groups: systems with weak ternary interaction and systems with strong or middleternary interaction. Systems with weak interaction are formed by binary systems, in one of which binary compounds are not formed. In all boundary binary systems that form a ternary system with a strong ternary interaction, binary compounds are formed. The first group includes systems Ti–MIV-VI–p-element, Fe – MVIII – R and Ti- Sn-Ga, Fe-Mn-Ce, the second – systems Ti – MVIII – Sn, Zr-Co-Sn, Fe-РЗМ-С.
A prediction of the phase diagrams of unstudied Fe-R-Co systems is made.
The systems Ti – MVII-VIII– Sn and Zr-Co-Sn are characterized by a noticeable ternary interaction and, consequently, the formation of ternary compounds, because in all boundary binary systems compounds are formed. The number of ternary compounds in the Ti – MVII-VIII, Ib – Si systems is much higher than in the Ti – MVII-VIII, Ib – Sn systems. The largest number of ternary compounds is formed in systems of cobalt and nickel, the least – in systems of iron and copper. This representthe increase of energy of binary interaction in systems from manganese to cobalt / nickel and a sharp decrease to copper, which correlates with number of valence electrons of metal MVII-VIII, Ib.
The most typical ternary compounds in the MIV-VI-MVII-VIII, Ib-Sn and Ti-MVII-VIII, Ib-Sn systemsare Heusler phases M1M2Sn (for titanium systems – TiMSn, half-Heusler phase, HH) and M1M22Sn (for titanium systems – TiM2Sn, Heusler phase, H). The temperature formation of these compounds also has a parabolic dependence on number of valence electrons of metal MVII-VIII, Ib. The temperature formation of H phases is higher than HH phases. This is due to order and occupation of crystallographic positions in structure of H phases, while structure of НН phases is subtraction phase with respect to H. Changing method of formation of Heusler (H) and half-Heusler (HH) phases from number of valence electrons are opposite. Thus, the TiM2Sn phases with cobalt and nickel melt congruently, with copper – is formed in the solid state. TiMSn phaseson the contrary, with cobalt are formed in the solid state, with nickel and copper –by peritectic reaction.
Keywords: titanium, iron, transition metals, rare earth metals, phase digram, liquidus, solidus, isothermal section, vertiсal section.
