Phase relations in the Tl2 Te–TlBiТe2 –TlTbTe2 system

The phase equilibria in the Tl2Te–TlBiТe2–TlTbTe2 concentration area of the Tl–Bi–Tb-Te quaternary system were investigated by using the differential thermal analysis and powder X-ray diffraction techniques. The diagram of the solid-phase equilibria of this system at room temperature was constructed. It was established that the Tl9BiTe6–Tl9TbTe6 section divides the Tl2Te–TlBiТe2–TlTbTe2 system into two independent subsystems. It was found that the Tl2Te–Tl9BiTe6–Tl9TbTe6 subsystem is characterized by the formation of a wide field of solid solutions with a Tl5Te3 structure (δ-phase) that occupy more than 90% of the area of the concentration triangle. The results of X-ray phase analysis of alloys of the Tl9BiTe6–Tl9TbTe6–TlTbTe2–TlBiТe2 subsystem showed the formation of wide regions of solid solutions based on TlTbTe2 and TlBiTe2 along the section of TlTbTe2–TlBiTe2 ((β1- and β2-phases) and made it possible to determine the location of the heterogeneous phase regions in this subsystem. The parameters of crystal lattices of mutually saturated compositions of the β1-, β2-, and δ-phases are calculated from powder diffraction patterns.The paper also presents some polythermal sections, isothermal sections at 740 and 780 K of the phase diagram, as well as projections of the liquidus and solidus surfaces of the Tl2Te–Tl9BiТe6–Tl9TbTe6 subsystem. The liquidus surface consists of three fields of the primary crystallization of α (Tl2Te)-, δ- and β1-phase. The constructed isothermal sections clearly demonstrate that the directions of the tie lines do not coincide with the T–x planes of the studied internal sections, which is characteristic of non-quasi-binary polythermal sections. The obtained new phases are of interest as potential thermoelectric and magnetic materials.

3D computer model of the Ag-Cu-Ni T-x-y diagram: verification of sections in the atlas of phase diagrams for lead-free soldering

Spatial (three-dimensional - 3D) computer model of the T-x-y diagram of the Ag - Cu - Ni system, which is promising for the development of environmentally friendly solders, is presented. The model is constructed on the basis of published data on the binary systems forming this ternary system, the concentration projection of the liquidus surfaces, and four isothermal sections. It is shown that the phase diagram (PD) consists of 14 surfaces and 9 phase regions. The adequacy of the model is confirmed by comparing the isothermal sections and the liquidus projection.

Phase equilibria of the Al-Co-Er system at 400°C and 600°C

The 400?C and 600?C isothermal sections of the Al-Co-Er system were studied assisted with X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) techniques. 18 three-phase fields were identified in the 400?C isothermal section. The maximum solid solubilities of Al in Co3Er and Co2Er were 13.93 at.% and 16.13 at.%, respectively. Whereas the maximum solid solubilities of Co in Al2Er, Al2Er3 and AlEr2 were 6.93 at.%, 6.65 at.%, and 6.49 at.%, respectively. And the solid solution range of ? is from 22.22 at.% Al to 44.44 at.% Al. While the 600?C isothermal section included 20 three-phase fields. The maximum solid solubilities of Al in Co17Er2 and Co7Er2 were 10.17 at.% and 10.24 at.%, respectively. Whereas the maximum solid solubilities of Co in Al2Er and Al2Er3 were 3.63 at.% and 2.01 at.%, respectively.

Thermodynamic assessment of the Fe-Nb-Si system

Nb-Si based alloys have drawn continuously increasing attention due to their excellent high-temperature mechanical properties. The addition of element Fe could improve their poor high-temperature oxidation resistance which largely restricts their applications. With the aim to study the effect of Fe addition on the Nb-Si system and to design appropriate alloy composition, the Fe-Nb-Si ternary system has been thermodynamically investigated using the CALPHAD (CALculation of PHAse Diagrams) approach aided with the formation enthalpies for ternary compounds at 0 K computed via ab initio calculations. A self-consistent thermodynamic description of the Fe-Nb-Si system was obtained in this work. Key isothermal sections and liquidus projection were presented, and the calculation results show a good agreement with available experimental data.