From simple binary to complex multicomponent eutectic alloys

The eutectic solidification of almost all binary and majority of key ternary alloy systems have been studied and modelled extensively. The development of eutectic microstructure in ternary, multicomponent and high entropy alloys have generated potential engineering alloys with superior mechanical/magnetic properties that outperform their traditional binary eutectic counterparts due to refined microstructure and/or the presence of dual hard/soft phase mixture. Currently, our understanding of the eutectic solidification is mainly restricted to alloy systems having upto 3 constituents (eg. ternary eutectic). There exists a knowledge gap in our understanding of the solidification behaviour of high order multicomponent eutectic alloys. This review article gives a brief background of the development of eutectic alloys from binary to senary multicomponent systems, together with an overview of recent development of complex microstructures of aluminium based multicomponent alloys with five or more constituents at/near eutectic compositions. Although the number of crystalline phases coexisted in the Al-based eutectic alloys increases with increasing number of constituents. The solidification of a melt at near eutectic composition of 13-element alloy system has led to the development of seven crystalline phases with predominantly non-cooperative growth, leading to a microstructure free of lamellar feature, as compared to their low-order constituent alloy counterparts. Finally, the hardness of Al-based eutectic alloy increases significantly as the number of constituents in excess of ten. This opens up a new opportunity to develop ultrahigh strength alloys based on high-order multicomponent eutectic alloy systems.

Automated summary

The eutectic solidification of binary and ternary alloys has been extensively studied, leading to the development of high entropy alloys with superior properties. However, there is a knowledge gap in understanding the solidification behavior of high order multicomponent eutectic alloys. The hardness of Al-based eutectic alloys increases significantly with an increasing number of constituents, offering new opportunities for developing ultrahigh strength alloys.