The Calculation of Phase Diagrams in High Entropy Alloys

High entropy alloy, with excellent properties such as high
temperature thermal stability, corrosion resistance, high strength,
hardness, high oxidation resistance, has improved material properties
compared to traditional alloy. High entropy alloy creates a
brand-new field of metal materials and becomes a new potential
material for development.
In this study, the main focus is based on Cu-Co-Ni-Cr-Al-Fe
system alloy with multi-components. Commercial software Thermal
Calc. is used to set up the database of this multi-components system
alloys and to select an appropriate thermodynamic module for the
simulation of phase diagrams. Then, by changing the contents of Al
and Fe, phase diagrams of Cu-Co-Ni-Cr-Al-Fe multi-components
system alloys are plotted.
At the same time, the designed alloy is synthesized by an
arc-melting and casting method. These samples were observed under
optical microscope and then identified by electron microscope
analysis, X-ray analysis, and thermal analysis (high-temperature
DSC) to verify the result of the simulation. Dendrite and inter-dendrite
structures were observed in these systems of alloys. By energy
dispersive spectrometry analysis, Cu enriched inter-dendrite structure
IV
was obtained. With more addition of aluminum (x=1), the dendrite
subsequently transformed into net-like structure due to the
decomposition of spinodal.
The specimens are heat treated and quenched under a specific
temperature determined by thermal analysis measurement and
analyzed in order to assess the accuracy of the simulated phase
diagram. X-ray analysis results indicated that each element would
solute reciprocally in a single BCC or FCC crystal structure.Therefore,
these results indicated that the experimental phase diagrams reflected
roughly with the calculated phase diagrams.