Mechanical and thermodynamic data-driven design of Al-Co-Cr-Fe-Ni multi-principal element alloys

Data-driven materials design is a modern approach, which is particularly desired for complex systems, such as the multi-principal element alloy (MPEA), also known as the high entropy alloy (HEA). The concept of MPEA/HEA brings tremendous opportunities of alloy design for superior mechanical properties, for instance, seeking for the ultimate goal of balanced strength and elongation in structural materials applications. Herein, we took the Al-Co-Cr-Fe-Ni quinary alloys as a model system to examine the semi-empirical method of alloy design based on empirical equations and high-throughput CALculation of PHAse Diagram (CALPHAD) modeling. The hardness, yield strength, ultimate tensile strength, and elongation of the as-cast Al-Co-Cr-Fe-Ni MPEA in the literatures were fit with the phase volume fraction of the fcc, bcc, and B2 phases. 10,000 CALPHAD solidification modeling based on the Scheil model were performed. Two alloys, Al₁₄Co₂₄Cr₂₂Fe₂₁Ni₁₉ (A1) and Al₁₆Co₂₃Cr₁₇Fe₁₉Ni₂₅ (A2), were cast and characterized with an X-ray diffractometer, a scanning electron microscope, a differential scanning calorimeter, hardness tests, and tensile tests. The semi-empirical method of combining empirical fitting of mechanical data in the literatures and thermodynamic calculation showed qualitatively agreements between experiments and predictions. While the CALPHAD modeling successfully interpreted the formation of phases and microstructures, the accuracy of empirical predictions can be further improved when more data are accessible for alloy and MPEA design under the guidance of calculations.