Fabrication of the high-entropy alloys and recent research trends: A review

Abstract

High-entropy alloys (HEAs), which are defined as a single phase crystalline solid solution with the composition of each constituent element in the range of 5-35 at%, have been the subject of intensive study in the last decade. Most of the HEA research is focused on alloy design, microstructural characterization, and mechanical testing, not manufacturing, processing, and industrialization, although the properties, microstructures, and performance are strongly dependent on processing. In this review article, we aim to describe the manufacturing processes applied to HEAs. The manufacturing process of HEAs can be classified into three main routes. First, liquid processing that includes arc melting, Bridgman solidification, atomization, and laser cladding is the most commonly used methods because the processing facilities are already widespread in many laboratory and the liquid processing can be easily scaled-up for commercialization. Second, mechanical alloying, i.e. powder metallurgy, is a process starting from a solid particle state and employing sintering procedures for bulk manufacturing. In particular, the mechanical alloying has been used for achieving super saturated solid solution which cannot be obtaiend using the conventional liquid prcesses. Third, the HEAs can be manufactured by mixing elements of the vapor state, which includes sputter deposition, atomic layer deposition, and vapor phase deposition. Explanation and comparison between various manufacturing methods of the HEAs are systematically described and demonstrated in this review.