摘要
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.
本文引入Friedel振荡理论,揭示固溶体合金中存在类似分子式的结构单元,指出在特定的成分下,合金中的原子在近程序上倾向于聚集为理想的有序结构,这个结构包括最近邻壳层原子(记作团簇)和次近邻壳层原子(记作连接原子),用团簇式:[团簇](连接原子)来表示.这种近程序结构被称为化学结构单元,类似于固溶体中的"分子".本文给出了FCC结构固溶体合金中化学结构单元的计算公式,通过计算得到Cu基二元体系的理想化学结构单元,包括CuZn、Cu-Al、Cu-Ni、Cu-Be和Cu-Sn,均为工业中最常用的合金成分.此外,工业上常用的多元合金,如Al合金5083和7075、高温合金TMS-196和TMS-82、马氏体时效不锈钢Cutom-465和奥氏体不锈钢310s,其成分均满足模型的预测,表明本模型可以为FCC结构复杂固溶体合金的成分设计提供理论指导.
作者
Dandan Dong
Qing Wang
Chuang Dong
Tai-Gang Nieh
董丹丹;王清;董闯;Tai-Gang Nieh(College of Physical Science and Technology,Dalian University,Dalian 116622,China;School of Materials Science and Engineering,Dalian Jiaotong University,Dalian 116028,China;Key Laboratory for Materials Modification by Laser,Ion and Electron Beam(Dalian University of Technology),Ministry of Education,Dalian 116024,China;Hong Kong Institute for Advanced Study/Department of Materials Science and Engineering,City University of Hong Kong,Hong Kong,China;On leave from Department of Materials Science and Engineering,University of Tennessee,Knoxville,37996-2100,Tennessee,USA)
基金
supported by the National Natural Science Foundation of China(51801017)
the Key Discipline and Major Project of Dalian Science and Technology Innovation Foundation(2020JJ25CY004)
the Subject Development Foundation of Key Laboratory of Surface Physics and Chemistry(XKFZ201706)
the State Key Lab of Advanced Metals and Materials(2018-Z03)
the Scientific Challenge Program for National Defense Basic Scientific Research(TZ2016004)
supported by the US National Science Foundation under Contract DMR-0905979。
