T-X-Y diagrams of lead-free soldering systems with thermodynamic contours of minimal surfaces

Alternative principle of the phase diagrams (PD) engineering has been offered: 1) before proceeding with the assembly of hypothetical or real PD, a space scheme of monovariant reactions (three-phase regions scheme) is to be elaborated; 2) contours of the surfaces with the unruled nature are to be closed and data of thermodynamic calculations are used on this stage; 3) surfaces should be approximated as the minimal ones, like the soap films, with the minimal area; 4) all geometrical elements (points, lines, surfaces, phase regions) are designated, and their “names” contain the meaning (reason) of these designations; 5) after the computer assembling the PD space model is a useful tool to solve different fundamental and applied tasks of materials science. E.g. solidification paths are confirmed by the mass balances: a vertical one - for the given centre of masses, and a horizontal one - for the isothermal state of isopleth. As computer model of PD saves information about system in compact form and permits to receive any projection, isotherm and isopleth with the decoding of intersected surfaces and phase regions, it helps also to enquire the errors and incorrectly interpreted experimental data, especially in the cases of surfaces’ degeneration because of negligibly small sizes of homogeneous regions. To investigate a competition of tiny eutectical crystals with more large primary crystals of the same phase in the invariant reaction with melt, an idea of “disperse” tie-line is used, and as a result the microstructures can be located with large, small and with mixed type of crystals. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2055