Fundamentals of High Entropy Alloys

High-entropy alloys (HEAs) are a new class of materials which are defined as alloys consisting of four or more base elements with equal or non-equal fractions. The high configurational entropy which is induced by the number of base elements is able to prevent the formation of intermetallic phases, and thereby avoids the disadvantages of conventional multicomponent alloys. HEAs mainly consist of simple solid solution structures, such as body-centered cubic (BCC), face-centered cubic (FCC), or hexagonal close-packed (HCP) structures. Many HEA systems reported are based on transition metals-namely Co, Cr, Fe, and Ni-with the additions of such elements as Al and Mn. The widely studied AlxCoCrFeNi HEAs are demonstrated from FCC to BCC structures through a mixture of both phases with increased Al content. The goal of this research is making high entropy alloy AlxCoCrFeNi (x=0, 1.25, 2) by microwave mechanical- combustion alloying. In most of the mechanical alloying methods, solid solution forms after more than 40 hours. In this research after 15 hours of mechanical alloying, alloy powder is pressed and lies under microwave combustion.