Microstructure characterization of AlxCoCrCuFeNi high-entropy alloy system with multiprincipal elements

A new approach for the design of alloy systems with multiprincipal elements is presented in this research. The AlxCoCrCuFeNi alloys with different aluminum contents (i.e., x values in molar ratio, X = 0 to 3.0) were synthesized using a well-developed arc-melting and casting method. These alloys possessed simple fcc/bcc structures, and their phase diagram was predicted by microstructure characterization and differential thermal analyses. With little aluminum addition, the alloys were composed of a simple fcc solid-solution structure. As the aluminurn content reached x = 0.8, a bcc structure appeared and constructed with mixed fcc and bcc eutectic phases. Spinodal decomposition Occurred further on when the aluminum contents were higher than x = 1.0, leading to the formation of modulated plate structures. A single ordered bee structure was obtained for aluminum contents larger than x = 2.8. The effects of high mixing entropy and sluggish cooperative diffusion enhance the formation of simple solid-solution phases and submicronic structures with nanoprecipitates in the alloys with multiprincipal elements rather than intermetallic compounds.