The Atomistic 2nd Law of Thermodynamics and its necessary and sufficient condition can be used to explain the phase diagrams of one or two components. In these explanations, the molar total chemical potentials of atomistic features play important roles, while the common tangent and lever rule are useful. In explaining the microstructural evolution at a composition of a binary phase diagram, the driving force, mobility of atomistic features and lever rule etc. are applied. Recently the use of machines or AI in the optimization of material properties is highly valued. More effective results could be obtained if the user of these tools have better understanding of the Atomistic 2nd Law of Thermodynamics and kinetics. The discussed topics are: T-T-T curve, T-T-T curve of 1080 steel, T-T-T of other materials, contains low-melting impurities.
