Maria Parfenova

Abstract:

The detailed analysis of ternary systems that form the quinary Ag-Au-Cu-Ni-Sn has been performed to assemble 3D computer models of T-x-y diagrams. The usual 3 steps were followed [1]: (1) scheme of mono- and non-variant states in table and space (3D) forms, (2) phase diagram (PD) prototype and (3) T-x-y diagram of the real system. E.g., there are 14 invariant transformations within the system Ag-Cu-Sn (6 of them with the liquid phase participation). As a result, T-x-y diagram, Ag-Cu-Sn includes 56 horizontal (isothermal) planes and 111 ruled surfaces. Besides, it is formed by 8 pairs of liquidus and solidus surfaces, 4 surfaces of transus and 54 surfaces of solvus (33 of them is degenerated into the vertical edges of the prism). In total, PD consists of 241surfaces and 88 phase regions. Space (3D) computer model was tested by 3 isothermal and 5 polythermal cuts in the Atlas [2]. Errors were found: on isothermal cut 221^оC in [2, p. 179] which is pictured an extra phase region L+C+R2, and on the isopleths via point Е an extra phase region L+R2+R8 is depicted. An error, that violates the rule of contacting state spaces (two two- phase regions are adjacent), and three more inaccuracies are found [2, c. 181] on the isopleth А-S (0, 0.82, 0.18). Other 3 isopleths don’t contain the contradictions between the [2] and model variants. Analysis of all four ternary systems, forming the Ag-Cu-Ni-Sn quaternary system (A- B-C-D), led to a scheme of di-, mono and invariant states, formally describing the geometric structure of the T-x-y-z diagram. According to this scheme, it’s possible to say, that T-x-y-z diagram contains 11 hypersurfaces of liquidus and the region of liquid immiscibility. In addition to Ag (A), Sn (D) and Cu (Ni) or B (C) solid solution, as well as seven compounds, including the R3 (R9) solid solution, there is an internal liquidus surfaces of the R11 compound and a low- temperature polymorphic modification of the R9 (Ni 3 Sn) compound. Seven invariant transformations are expected, including five of quasiperitectical type, one - euthetic and one of polymorphic transformation between allotropic forms of Ni3Sn2. Partial validation of the geometric structure forecast of the quaternary system liquidus can be carried out based on the experiments [3-4] with alloys, rich in Sn (80, 90, 95 and 97 at. %) at 210^oC and at 250^oC. This work was been performed under the program of fundamental research SB RAS (project 0336- 2019-0008), and it was partially supported by the RFBR project 19-38-90035.