Thermodynamic Database for Multi-Principal Element Alloys Within the System Al–Co–Cr–Fe–Mn–Ni–C

The development of multi-principal element alloys requires the navigation within a multi-dimensional composition space, which has proven to be challenging. Various methods to predict the state of an alloy, in particular if it is single-phase or not, have been tested with various success. The only approach that can consistently predict the constitution of an alloy, e.g. single-phase, multi-phase, intermetallics, is thermodynamic calculations using Calphad databases. Conventional Calphad databases, such as steel or Ni-base, are of limited use since they are developed for alloys with a specific base element. More suitable databases, such as TCHEA, have been developed, but their development is challenging since they require the inclusion of more subsystems than conventional databases. The predictive capability depends strongly on which elements are considered, and their development is still ongoing. A Calphad database including the elements Al, Co, Cr, Fe, Mn, Ni and C was built up from scratch using mostly assessments of binary and ternary systems from the literature, but with many amendments. This database covers a substantial fraction of the alloys investigated until now plus the element C that is usually not included, but can provide additional strengthening, either in solution or in the form of carbides.