A new approach to determine/design the eutectic composition of binary, ternary, and high-entropy alloys using electromagnetic directional crystallization

Abstract

Eutectic materials have been widely employed in many high-tech fields, and recently, eutectic high-entropy alloys (EHEAs) have become a research focus of eutectic materials; however, it is challenging to determine/design the eutectic composition of alloys accurately, especially multi-component alloys and EHEAs. In this study, a new electromagnetic directional crystallization approach was proposed to determine/design eutectic alloy compositions. First, standard eutectic Al-Si, Al-Si-Fe, Al-Si-Ti, and Al-Si-Fe-Mn alloys were obtained by directly separating their respective melts using electromagnetic directional crystallization. Then their eutectic compositions were accurately determined by inductively coupled plasma-optical emission spectroscopy. Conflicting reports about the eutectic reactions and phase transformations occurring in the Al-Si-Ti system were also resolved. Thereafter, the application of electromagnetic directional crystallization was extended to EHEAs. The widely investigated AlCoCrFeNi 2.1 EHEA was confirmed to have a eutectic composition, and a new EHEA Al 16.8 Co 12.6 Cr 13.8 Fe 11.8 Ni 45.1 with a combination of high strength and high ductility was obtained in this study by separating the AlCoCrFeNi 3 melt via electromagnetic directional crystallization. Therefore, in the absence of thermodynamic data, electromagnetic directional crystallization provides a promising approach for determining and designing the eutectic composition of alloys, especially EHEAs. This new approach is more direct, efficient, and simpler than the conventional thermodynamic-calculation approach because the application of the latter is significantly limited when thermodynamic data are not available. • A new approach is proposed to design eutectic high-entropy alloys without thermodynamic calculation. • A new eutectic high-entropy alloys, Al 16.8 Co 12.6 Cr 13.8 Fe 11.8 Ni 45.1 , was designed and reported. • Standard eutectic alloys were prepared through one-step electromagnetic directional crystallization. • Controversial research results about AlCoCrFeNi 2.1 alloy and the Al-Si-Ti system were finally solved.