CALPHAD is an acronym for CALculation of Phase Diagram. An equilibrium diagram is a diagram representing the temperatures and components of a chemical system. The diagram usually indicates the regions whereby any substance or solutions, which are the phases, are stable and also regions where combined substances or solutions can coexist.
Phase diagrams are considered to be very effective tools for coming up with characteristics of a system that is subjected to different conditions. Initially they were a graphical technique used to determine experimental data on the state of equilibrium. The CALPHAD concept is focused on the fact that a phase diagram is a manifestation of the equilibrium thermodynamic characteristics of a system, which are a combination of the characteristics of the each of the phases.
The origins of CALPHAD date back to over 40 years ago when Hino Ansara and Larry Kaufman came up with the idea to gather around various scientists who had previously researched on the experiments of alloy phase diagrams as the foundation that was required for the constant nature of the experimental thermodynamics and phase diagram collected data.
It was at that first conference that the term CALPHAD was used for the first time and the subsequent changes thereafter were associated with the computational combination of phase diagrams and thermochemistry. It is from the basis of these original CALPHAD method and subsequent successes that the method has been widely used in various areas of material development.
There is are information resources in the form of a paper that depicts the evolution of CALPHAD, presenting a brief account with certain focus on the formative years defining its creation and growth. The ultimate design of the industrial application of CALPHAD requires reliable thermodynamic data. There is ongoing research focussed on computational thermodynamics to support the development of tools and calculations that will help in improvement of the understanding of various industrial and technological processes.