Composition formulas of solid-solution alloys derived from chemical-short-range orders.

Solid solutions are the basis for most industrial alloys. However, the relationships between their characteristic short-range orders and chemical compositions have not been established. The present work combines Cowley parameter α with our cluster-plus-glue-atom model to accurately derive the chemical units of binary solid-solution alloys of face-centered cubic type. The chemical unit carries information on atomic structure and chemical composition, which explains prevailing industrial alloys. For example, chemical units in CuZn alloy with α = - 0.137 are formulated as [Zn-CuZn]ZnCu and [Zn-CuZn]ZnCu, with 64.0-70.0 wt% Cu corresponding to the most widely used cartridge brass C26000 (68.5-71.5 Cu). This work answers the long-standing question on the composition origin of solid-solution-based industrial alloys, by tracing to the molecule-like chemical units implied in chemical short-range ordering in solid solutions.