Phase equilibria and mechanical properties of Cr–Fe–Ni alloys: A CALPHAD–DFT integrated approach with experimental validation

This study investigates the Cr–Fe–Ni system from the Cr-rich corner for the alloys Cr10Fe20Ni, Cr30Fe2.5Ni, and Cr47.5Fe6.96Ni wt.% have been sintered by field-assisted sintering technology (FAST) at 900°C under 10MPa pressure with a holding time of 15 minutes, guided by the CALculation of PHAse Diagrams (CALPHAD) approach. Lattice parameter has been investigated by the first-principles Density Functional Theory (DFT) model. The alloys were successfully synthesized rapidly, to achieve a relative density of approximately 98%, as measured by the Archimedes method, with a uniform microstructure averaging a grain size of 35–65 μm, and crack-free ingots. X-ray diffraction patterns validate CALPHAD phases prediction precisely by characteristic peaks for the alloys Cr10Fe20Ni, Cr30Fe2.5Ni, and Cr47.5Fe6.96Ni wt.% correspond to the phases α-Cr (islands) (110) + γFeNi (matrix) (111), α-Cr (equiaxed grains) (110), and σ (321) + α-Cr (110) (partial interlocked network), respectively. Vickers hardness values of the alloys are 281.5, 325.75, and 347.25 HV, respectively. Thermogravimetric analysis (TGA) / Differential scanning calorimetry (DSC) reveals thermal stability up to 1000°C. On the other hand, at elevated temperatures up to 1200°C, alloys show phase change evaluation. The increase in Ni content has a direct effect on the alloy's thermal properties.