Molecule-like chemical units in metallic alloys

Each conventional alloy has its own specific compositions but the compositional origin is largely unknown due to our insufficient understanding about chemical shortrange ordering in the alloy,in particular,in the solid-solution state.In the present paper,the compositions of metallic alloys are discussed and formulated,by unveiling the basic moleculelike structural units in solid solutions.Friedel oscillation theory,which describes the partial charge screening behavior in solid solutions,and henceforth the origin of short-range ordering,is applied to pin down the ideal chemical compositions of conventional metallic alloys.We propose that,at a specific composition,atoms self-assemble into an ideally ordered structure consisting of atoms residing in the nearestneighbor shell(denoted as cluster)plus those in the next outer shell(denoted as glue atoms),which can be formulated as[cluster](glue atoms).This simplified version of short-rangeorder structure represents the smallest charge-neutral and mean-density zone(termed as“chemical units”)and can be regarded as the‘molecules’of solid solutions.Accordingly,the chemical units and the corresponding molecule-like formulas for face-centered-cubic(FCC),hexagonal close-packed(HCP),and body-centered cubic(BCC)structures are analyzed and equations are obtained to identify the chemical formulas for FCC solid solutions.For instance,well-knownα-brass Cu-30 Zn alloy is formulated as[Zn-Cu_(12)]Zn4.Examples of aluminum alloys,superalloys and stainless steels are also illustrated,demonstrating the versatility of the present model to interpret chemically complex alloys.

Research of chemical induction unit on mixing effect and chlorine saving

Rapid mixing and chlorine saving are two important problems that most drinking water industries are focus on, and this paper adopts chemical induction unit to compare with water jet injector to study what merits chemical induction unit has. The experiment chose coefficient of variability of chlorine concentration to evaluate the mix effect and used chlorine consumption to compare the two equipments. Distribution reservoir experiments show that chemical induction unit can completely mix chlorine less than 6.2 seconds and water jet injector can not completely mix in 3 minutes. Mixing pool experiments show that chemical induction unit can save chlorine compared with water jet injector, and can save more if more chlorine is consumed.

Composition optimization of high-strength Mg-Gd-Y-Zr alloys based on the structural unit of Mg-Gd solid solution

Mg-Gd-Y-Zr alloys with high strength fall within narrow composition range.The present paper explains their composition rule by establishing the cluster-plus-glue-atom unit of Gd-containing Mg solid solution with the aid of Mg matrix and Mg_(5) Gd precipitate phase.First,based on the structural homologue between Gd-containing Mg solid solution and Mg_(5) Gd precipitate phase and in combination with our previously established method for calculating the glue atoms,[Gd-Mg_(12)]Mg_(5) is obtained as the chemical unit of Gd-containing Mg solid solution.Then,seven compositions are designed using different combinations of this unit and that of pure Mg[Mg-Mg_(12)Mg3.After a systematic experimental investigation on the microstructure and mechanical property evolutions as a function of the unit proportions,it is revealed that the Mg-10.1 Gd-3.3 Y-0.9 Zr alloy,being issued from equi-proportion mixing of the two units,shows the strongest tendency of precipitation and reaches the highest strength of 374 MPa after aging.The composition and strength of this alloy are quite close to GW103 K which is well recognized for its general mechanical performance in Mg-Gd-Y-Zr system.