Faasikarttoja

Faasikarttoja, or phase diagrams, are diagrams that map the stable and metastable phases of a material system as functions of variables such as temperature, composition, and sometimes pressure. They summarize thermodynamic information about which phases are energetically favorable under given conditions and show how phase assemblages change with heating or cooling. These diagrams are widely used in chemistry, metallurgy, materials science, and geology to understand and predict material behavior.

Most faasikarttoja depict systems with one or more components, with binary diagrams (two elements) being the simplest and ternary diagrams (three elements) more complex. Typical elements of a faasikartta include regions corresponding to single-phase stability (e.g., a pure liquid or a single solid phase) and multiphase regions where two or more phases coexist. Key features often shown are liquidus and solidus lines, invariant reactions such as eutectic, peritectic, or eutectoid points, and the compositions and temperatures where phase changes occur. The diagrams can be constructed from experimental data or computed from thermodynamic models using methods such as CALPHAD.

Applications of faasikarttoja include guiding alloy design, heat-treatment schedules, and material processing by predicting the phases that will form under specific cooling or heating paths. They also serve as educational tools to illustrate phase transformations. Limitations include the equilibrium assumption, neglect of kinetics and metastable states, and increasing complexity with more components, which can make high-dimensional diagrams difficult to visualize.