3/26/2023 0 Comments High entropy alloys![]() Miracle introduced another important term, multi-principal-element alloy (MPEA), which should be used when the community is interested in looking onlyĪt the central region of the complex composition space to avoid some of the confusion that results from the standard definition of HEA. However, Miracle noted, there are three issues with these two definitions: (1) solid solutions are rarely ideal, even in the liquid state (2) people incorrectly believe that in order to be classified as an HEA, the material must be both a single-phase and solid solution and (3) the composition-based and entropy-based definitions have some contradictions. According to Miracle, both definitions support the motivation of favoring solid solution formation through configurational entropy while placing no restrictions on phase numbers or types. Two definitions currently exist within the HEA community, Miracle continued-one is composition-based (composed of five or more principal elements, each with a concentration between 5 and 35 atomic percent), while the other is entropy-based (retains an ideal, configurational entropy greater than or equal to 1.61 R, where R is the gas constant). ![]() Although both ideas are compelling, Miracle asserted that the latter is not as well supported by experimental data as the former. High-Entropy Materials AN ASSESSMENT OF THE HIGH-ENTROPY FIELDĭaniel Miracle, Senior Scientist, Air Force Research Laboratoryĭaniel Miracle highlighted the two fundamental objectives that exist in the high-entropy alloy (HEA) community: (1) to examine the unknown central region of multicomponent alloy phase space ( Cantor et al., 2004) and (2) to favor solid solutions over intermetallic phases by regulating the configurational entropy in complex alloys ( Yeh et al., 2004). ![]()
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