金属玻璃和固溶体合金的成分根源：近程序结构单元

发布时间：2018-04-17 20:19

  本文选题：金属玻璃 + 固溶体合金　； 参考：《大连理工大学》2017年博士论文

【摘要】：本论文将针对金属玻璃和固溶体合金的成分根源进行研究。这两类合金在特定成分下会具有特殊的性能,这些特定成分都是经过长期大量的实验探索而得,人们迫切需要理解其成分背后的结构根源,从而建立有效的成分设计理论,以指导合金研发。鉴于这些合金均呈现近程有序结构,本课题组前期工作利用团簇加连接原子模型实现了对近程有序结构的描述,经验式地提出了合金具有特定的"第一近邻团簇加若干连接原子"成分式,但是在成分式的获得上一直存在物理基础不明确、经验推断过多等缺点,包括第一近邻的准确定义、团簇的选择以及连接原子的定量确定。本论文将针对上述关键问题进行研究,通过引入电子的Friedel振荡和球周期,完善了描述近程序结构的团簇加连接原子模型,提出了类似于分子式的合金化学结构单元,并实现了其定量计算。由此,本工作揭示了金属玻璃和固溶体合金的成分根源,推出了统一的成分式规则,发展了合金成分设计的理论基础。具体的工作内容涵盖以下四个方面:(1)首先引入电子的Friedel振荡解决第一近邻多面体团簇的定义问题。第一近邻的确定一直缺乏物理机制,尤其是团簇第一近邻原子分布在多个壳层上时,团簇的截断距离无法确定。本论文通过引入电子的Friedel振荡机制和原子密堆判据,给出了截断距离的明确定义,并指出团簇的最近邻壳层被Friedel振荡势函数中第一个最小值的范围所限制。团簇中"中心原子-最外层原子"和"中心原子-最内层原子"的距离分别为rL和rS利用Friedel振荡得到rL/rs的上限为1.5。随后在硬球原子密堆的前提下,进一步将rL/rS与原子半径比和团簇表面覆盖构型建立关联,给出不同情况下rL/rS的比值。将rL/rS与测得的rS相乘,最终得到团簇的截断距离,并且在常见的团簇构型中得到验证。(2)其次,解决了进入金属玻璃成分式的团簇的精确选择问题。金属玻璃相关的合金相中通常含有多个非等效的原子占位,以任一个原子占位为心都可以定义出一个团簇,从这些团簇中选取出最具代表性的主团簇是需要解决的关键问题。本论文强调了主团簇的两个重要的特征:球周期性和团簇间距,同时也是金属玻璃的两个结构特征。利用这两个特征给出了二元块体金属玻璃相关合金相中主团簇的严格定义,并利用这些主团簇解释了二元块体金属玻璃成分,包括Cu-Zr、Cu-Hf、Ni-Nb、Ni-Ta、Al-Ca和Pd-Si体系。(3)提出了描述固溶体近程序的化学结构单元并实现了其定量计算。认为接近熔点的熔体与随后形成的固溶体之间存在类似的近程序结构遗传。通过将团簇共振模型引入到固溶体结构的中程序描述中,指出理想满足原子间作用的团簇加连接原子成分式就是类似于分子式的化学结构单元,而作为核心近程序结构从液态遗传到固溶体态,并得到了结构单元的计算公式,Z=c ·ρa·r13,其中c为常数,ρa为原子密度(单位体积原子个数),r1为团簇半径。利用这个公式计算得到了典型FCC结构工业合金中的化学结构单元,包括二元Cu基工业合金、Ni基单晶高温合金以及无Co马氏体时效不锈钢,其结果与最常用的合金牌号吻合,从而揭示出工业合金的成分根源在于具有特定结构的化学结构单元。(4)建立了具有焊料背景的Sn基共晶点的双团簇模型。本课题组之前的工作提出了共晶液体的双团簇模型,即共晶液体由两个稳定的液体结构单元构成,这两个结构单元分别来自两个共晶相,结构单元可以用理想金属玻璃的团簇式表示。Sn基共晶点多靠近β-Sn一侧,不能用上述双团簇模型解释。共晶点中Sn含量较高,因此可以假设构成共晶液体的两个结构单元都基于β-Sn结构,这样就可以利用上一章中固溶体结构单元的计算方法进行团簇式的计算。首先计算出β-Sn结构中的化学结构单元为[Sn-Sn10]Sn5,即配位数为10的团簇加上5个连接原子。然后将另一种元素当作溶质,根据公式Z=c·ρa·r13 计算出具体的团簇式形式。利用双团簇成分式解析了简单Sn基二元共晶点,包括Sn-(Ag,Au,Mg,Pb,Zn,Bi)。最后根据这些双团簇式,解析了典型Sn基共晶钎料成分,指出多组元Sn基共晶钎料中微合金化元素的添加一般是通过对基础二元成分进行整数个原子的替换实现的,从而为Sn基共晶钎料的成分设计提供了一种新的方法。
[Abstract]:This paper will research on metal glass and solid solution alloy composition of roots. The two kinds of alloy will have special properties in specific components, these specific components is through long-term experiments and exploration, the root of people need to understand the source behind the components, so as to establish the effective theory of composition design to guide, alloy research and development. In view of these alloys showed a short-range ordered structure, ourprevious work using cluster plus glue atom model for short-range ordered structure description, empirical formula proposed alloy has specific "nearest neighbor clusters with several atomic components, but the connection" in component there has been on the physical basis is not clear, too much experience and other shortcomings, including the accurate definition of the first nearest neighbor, determine the cluster selection and quantitative connection of the atoms. This paper will address. Research on the key problems, through the introduction of electronic Friedel oscillation and ball cycle, improve the structure of the program described near cluster plus glue atom model, put forward the chemical structure of alloy unit similar to the molecular formula, and realizes the quantitative calculation. Thus, this work reveals a metal glass and solid solution alloys the root, launched a unified composition rules, the development of the theoretical basis of alloy composition design. The main content covers the following four aspects: (1) the definition of the problem first introduced Friedel electron oscillation solution of first neighbor polyhedron clusters. The first neighbor has been the lack of physical mechanism, especially the first nearest neighbor cluster the distribution of atoms in multiple shell, cut distance cluster cannot be determined. This paper introduced the electronic Friedel oscillation mechanism and atomic packing criterion, given truncation distance defined, And pointed out that the cluster nearest neighbor shell is restricted by the first minimum value in the range of Friedel oscillation potential function. The cluster "central atom - the outermost atomic" and the "central atom of the innermost atomic distance were rL and rS by Friedel rL/rs of the upper limit of 1.5. oscillation was then in the hard sphere packing density the atom under the premise of further rL/rS with atomic radius ratio and cluster configuration of surface coverage, given the ratio under different conditions of rL/rS. RL/rS and rS measured by multiplying the truncation distance obtained clusters, and verified in the cluster configuration in common (2). Secondly, to solve the the precise selection problem into clusters. The composition of metallic glass alloy metal glass phase usually contains a number of non equivalent atoms occupying, with any of the atoms occupying heart can define a cluster, from these clusters in selecting the most The main cluster representative is the key problem to be solved. This paper emphasizes two important characteristics of the main clusters: Ball periodicity and cluster spacing, and two structural features is given by the metallic glass. The two features a strict definition of two yuan bulk metallic glass alloy related main phase the cluster, and use the main cluster explained two yuan bulk metallic glass components, including Cu-Zr, Cu-Hf, Ni-Nb, Ni-Ta, Al-Ca and Pd-Si system. (3) proposed chemical structure description of the unit solid solution near program and achieve its quantitative calculation. That close to the melting point and then melt the formation of solid solution are similar in genetic structure between programs through the cluster resonance model is introduced into the structure of solid solution in the program description, pointed out that the ideal meet cluster interaction and connection type atomic elements is similar to the molecular formula of chemical structure The unit, which is the core in the program structure from the liquid solid solution to the genetic body, and the calculate formula of the structural unit, Z=c p a R13, where C is a constant, a refers to the atomic density (number of atoms per unit volume), R1 as the cluster radius. Using this formula to calculate the chemical structure the typical structure of industrial unit FCC alloy, including two Cu based alloy industry, and Ni based single crystal superalloy Co maraging stainless steel, the most commonly used alloy anastomosis, so as to reveal the composition of alloy is the root of industrial chemical structure units with specific structure. (4) two clusters the model established with Sn based solder background of the eutectic point. The eutectic liquid cluster model of our group work, which is composed of two stable eutectic liquid liquid structure unit, the two units were from two eutectic phase, 缁撴瀯鍗曞厓鍙�浠ョ敤鐞嗘兂閲戝睘鐜荤拑鐨勫洟绨囧紡琛ㄧぃ�

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