EFFECT OF METAL-OXIDE DIFFUSION BARRIER ON INTERDIFFUSION OF ELEMENTS BETWEEN COATING AND SUBSTRATE

The effect of LPPS Ni_3Al-Y_2O_3 diffusion barrier layer on interdiffusion of elements betweencoating and substrate has been investigated.It was found that the retardation of interdiffusionis related to the amount of oxide in the diffusion barrier layer.The retardation is not remark-able when the content of Y_2O_3 is 8 wt-%,whereas the diffusion of Al,Co or Cr has all beennotably retarded when the content of Y_2O_3 reaches 30 wt-%.The retardation effect of diffu-sion barrier is different for different elements such as Al,Co or Cr.     

Al/Ti扩散层形成的扩散溶解机制

分别在铝组元熔点之下和之上对Al/Ti镶嵌式扩散偶进行退火热处理,形成固-固和固-液扩散偶.利用光学显微镜、扫描电子显微镜和电子探针显微分析仪观察和分析Al/Ti固-固和固-液扩散层的形态和结构,并对其形成微观机理进行了研究.结果表明,Al/Ti固-固扩散层由一层TiAl₃构成;固-液扩散层由TiAl₃单相层与TiAl₃和Al(Ti)固溶体双相层两层构成,双相层TiAl₃和Al(Ti)固溶体的形态自铝向钛呈现规律性变化.Al/Ti固-固TiAl₃扩散层和固-液TiAl₃单相层的形成都是铝扩散溶解到钛中形成以钛为溶剂的Al-Ti固溶体结晶形成的;而Al/Ti固-液TiAl₃和Al(Ti)固溶体双相层是钛先溶解再扩散到液态铝中形成的Al-Ti液溶体结晶形成的.铝液中Ti原子浓度自铝向钛逐渐升高,导致了双相层TiAl₃和Al(Ti)固溶体形态的规律性变化.     

金属-氧化物扩散障对涂层和基体间元素互扩散的阻碍作用

本文研究了低压等离子喷涂的Ni_3Al-Y_2O_3扩散障层对外层涂层与基体间元素互扩散的阻碍作用,发现阻碍扩散的作用与扩散障层中氧化物含量有关。当Y_2O_3含量为8wt-%时,扩散障对元素互扩散没有明显的阻碍作用;当Y_2O_3含量为30wt%时,对Al,Co和Cr等元素的扩散有明显的阻碍作用。并且,阻碍作用随元素不同而不同。     

填充Co的CoCrCuFeNi高熵合金扩散焊接头的组织和扩散机制

在850,950,1050和1100℃下,填充Co中间层对CoCrCuFeNi高熵合金（HEA）进行了扩散焊接,并对接头微观组织和扩散机制进行了分析。结果表明,在各温度下接头均形成了牢固的结合,接头无金属间化合物生成,高熵合金侧界面周围残留部分柯肯达尔孔。对Cr、Fe、Cu和Ni在Co填充层中的扩散系数进行了计算,排序如下：Cu>Cr>Fe>Ni。所有元素的扩散速度均在相同水平,CoCrCuFeNi高熵合金和Co填充层之间的扩散是在空位机制和晶界扩散机制的共同作用下发生的。     

Ti／Al扩散焊的接头组织结构及其形成规律

以TA2和L4为焊接材料进行扩散焊，结合剪切断口形貌，XRD分析，SEM分析和接头强度测试，研究了Ti／Al扩散焊的接头形成规律。结果表明，接头形成过程包括互扩散形成冶金结合、冶金结合区生成新相、新相颗粒长大连接成片层、新相片层按照抛物线规律生长4个阶段。TiAl3是扩散反应的初生相，且在较长时间内是唯一生成相。它的生成具有一定延迟时间tD，tD受温度影响很大。接头强度取决于扩散区中冶金结合的程度及界面结构，在TiAl3新相连接成片层之后，接头强度达到甚至超过L4型Al母材。接头剪切断裂发生在界面扩散区的Al侧或Al母材内部。     

Reactive Diffusion in Ni-Si Bulk Diffusion Couples

Reactive diffusion in the Ni-Si system has been studied using bulk polycrystalline Ni/Si wafer diffusion couples in the temperature range from 450 to 700 °C and with annealing times of up to 32 h. For all diffusion couples, three phases were detected Ni₂Si, Ni₃Si₂, and NiSi. The thickness e of the reaction product is not homogeneous; its global growth kinetics satisfies the parabolic law and the total growth coefficient k ² (e ² = k ² t) is found to be expressed by: k ² = 2.5 × 10⁻⁴ exp (−160 kJ/RT), in m²/s. The Ni₂Si layer is homogeneous in thickness, and the value of its growth coefficient obtained by extrapolation at lower temperatures is more than two orders of magnitude smaller than the values obtained in thin-film experiments.     

LF6/TA2扩散焊接接头组织结构及性能

进行了LF6／TA2扩散焊接试验，结合断口形貌、XRD分析、能谱分析和接头强度测试，研究了Al，Mg，Ti三组元互扩散过程，给出了接头形成规律及其强度性能。结果表明，扩散焊接可以得到最高抗剪强度达83MPa的LF6／TA2接头；525℃以上扩散焊接时会发生扩散反应，生成唯一的三元金属间化合物新相Al18Ti2Mg3；接头强度受固溶冶金结合区及扩散反应新相区的影响，随前者增大而增大，随后者增大而减小；Al，Ti元素可以互扩散，但未发现有Mg元素向TA2母材中扩散的迹象；Al，Ti，Mg三元扩散反应产物按照近似线性的生长方式长大。     

SIMULATION OF THE CHANGE OF SINTERING NECK BETWEEN TWO GRAINS IN TWO DIMENSIONS

1.IntroductionThe powder sintering is an important process in powder metallurgy,in which complex changes oc-cur at elevated temperature;however,these changes are difficult to be observed directly.With the devel-opment of computer simulation,the simulation of powder sintering process have been carried out by anumber of researchers[1-6].For example,the simulation of the intermediate and last stages for ceramicpowder sintering have progressed to a certain extent,and the growth and evolution proce…     

"相变-扩散钎焊(T/DB)"新工艺及其接头界面形貌

为减小相变超塑性扩散连接的循环次数,提出了一种新型焊接工艺"相变-液相扩散焊(T/DB)",即在待焊母材间预先放入液相扩散焊用的中间层,然后按传统相变超塑性扩散连接工艺施焊,但要求温度循环的峰值温度须同时大于母材的相变点与中间层的熔点.试验以低碳钢为母材,以镍基非晶箔带(BNi2)为中间层,进行了低碳钢的相变-扩散钎焊(循环3次)与液相扩散焊接(1200℃×3 min)的对比试验.结果表明相变-液相扩散焊所需温度循环次数少,接头无界面空洞,其接合线呈非平面状;而液相扩散焊接头的接合线较平直.分析认为,界面的起伏是母材的适度溶解与超塑性流变共同作用的结果;非平面状界面有利于增大金属-金属接触面积及扩散通道的面积,为获得合格接头做出了相应贡献.     

扩散连接接头金属间化合物新相的形成机理

扩散连接接头中界面区脆性金属间化合物相的出现往往会造成接头性能的恶化,因此研究并建立接头界面区金属间化合物相的生成和成长行为的数学模型对扩散连接过程有非常重要的理论及现实意义。本文根据扩散理论,指出界面处生成相的动力学驱动力限决于扩散偶中组元自身的特性,生成机的组元及比例应按原子扩散通量比优先生成,本文从动力学及热力学角度出发,提出了多组元扩散偶界面处的金属间化合物生成相原则：通量-能量原则;并以钛/镍/钢扩散接接头为例,证明钛/镍界面处金属间化合物相的生成规律为Ni/TiNi3/TiNi/Ti2Ni/Ti。提出,通量-能量能力相当的两种或多种金属间化合物有可能同时形核篚,接头界面处会形成混合的金属间化合物。     

机械能助Al-Zn-Cr共渗工艺及渗层组织

采用机械能助渗技术,在600℃温度下对20钢进行Al-Zn-Cr共渗试验。利用光学显微镜、扫描电镜(SEM)、能谱仪(EDS)等仪器,分析合金元素铬对渗层组织共渗速率的影响,分析助渗时间对渗层组织的影响,测定铬在渗层中的分布,以及铬含量对渗层厚度的影响。结果表明:在机械能助Al-Zn-Cr共渗的研究中,铬含量的增加促进了渗层厚度的增加,而铬在渗层中分布相对均匀,无富集现象。在相同助渗时间下,铬含量的增加,促进了共渗速率的提高,促使渗层组织由单一的铁铝渗层组织转变为铁铝、铁锌多层渗层组织。在同一渗剂配比条件下,助渗时间的延长,促进Fe-Zn相形成,Fe-Al相减少。在助渗条件为600℃、3 h、5%Cr时,渗层为α-Fe(富锌)、Fe_3Zn_(10)、FeZn_7、FeAl等相组成的多层组织,而且相对致密;渗层兼顾抗氧化性和阴极保护作用。     

Solid-state displacement reactions in the Fe-Ni-S and Cu-Ni-S systems between 400 and 500°C

Solid-state displacement reactions of the type A+BSB+AS have been studied in the systems Fe-Ni-S and Cu-Ni-S. In diffusion couples, mainly of the type Fe/Ni₃S₂ and Cu/Ni₃S₂, the layer sequence, morphology, and growth rate of the reaction products have been investigated. The layer sequence of the reaction products in the couples appears to be just the reverse of that found previously in displacement reactions in some couples of oxide systems like Ni/Cu₂O and Co/Cu₂O. We find the sequence A/B/AS/BS, whereas in the oxide systems the sequence A/AO/B/BO has been found. This means that the metal atoms exchange and sulfide ions practically stand still in the first case, whereas in the oxide system the transport of oxygen is essential. For a correct interpretation of the results it was necessary to determine the isothermal cross-section through the Fe-Ni-S system at 460 and 500°C. At 500°C the iron stabilized high-temperature modification -Ni₃S₂ was found.     

VisiMat-Software for the Visualization of Multicomponent Diffusion in Two and Three Dimensions

VisiMat is a MATLAB code with a graphical user interface (GUI) that is intended to be used for instructional purposes. It is designed to facilitate understanding of the complex multicomponent diffusion phenomena that may occur in couples of three or more components with a special emphasis on the compositions and locations where maxima, minima, or zero-flux behavior may occur. VisiMat is an implementation of the square-root diffusivity method for predicting and visualizing the diffusion behavior of ternary and quaternary, single-phase, multicomponent diffusion couples with constant diffusivity. The program determines concentration profiles, fluxes including zero-flux conditions, and two- or three-dimensional representations of composition space and diffusion path. Although the code will accomodate any number of components, the three-dimensional visualizations are not possible for more than four components.     

金属扩散系数的测量方法与理论研究

介绍了金属扩散系数的几种测量方法,包括扩散对法、毛细管-熔池法、剪切单元法、转盘法和等离子轰击技术等;以及几种自扩散系数的理论研究和液态合金的扩散、自扩散系数的理论研究方法,包括硬球模型、线性轨道假说、小步扩散理论、流体动力学模型、经验公式及慢中子散射技术,液态合金中的扩散有Darken给出的互扩散系数及互扩散系数模型。通过对比各种实验方法的优缺点,分析实验值与理论计算值之间出现偏离的原因,指出了寻求有效的示踪原子是今后的研究动向,探索离子轰击能够促进扩散的原因将成为今后的研究重点。     

纯镁渗锌处理表面合金化机制研究

对纯镁进行了表面渗锌处理，研究了扩渗温度及扩渗时间对于合金化渗层组织、相结构及反应层连续性的影响。结果表明：扩渗温度的选择有一个合适的范围，温度过低，扩渗速度太慢甚至Zn元素原子的能量达不到其激活能，不能产生活性原子，扩渗过程无法进行。温度过高虽然有利于形成合金化渗层，但会使基体晶粒粗化，甚至改变整个基体，而且，温度过高不利于反应层（金属间化合物区）的稳定：扩渗时间的延长会促使Zn的进入量和金属间化合物的生成量增加，并削弱晶界扩散优势的影响，最终使固溶层和反应层趋于均匀化。要形成连续的反应层，扩渗温度应控制在400℃～420℃，相应的扩渗时间为8h以上。     

An examination of a multicomponent diffusion couple

New expressions relating the interdiffusion flux of a component to its own concentration gradient in a multicomponent diffusion couple have been derived and applied to a diffusion couple investigated in the Cu-Ni-Zn system. From these relations, effective interdiffusion coefficients were determined at selected sections in the diffusion zone directly from the locations of the sections relative to the Matano plane. The Cu-Ni-Zn couple was analyzed for interdiffusion fluxes and interdiffusion coefficients with the aid of “MultiDiFlux” program developed for the analysis of interdiffusion in multicomponent systems. The couple was examined for zero-flux plane development, interdiffusion against activity gradients, and diffusion path representation. Diffusion path slopes at selected sections in the diffusion zone were related to the interdiffusion coefficients; slopes at path ends were determined from eigenvectors evaluated from limiting ratios of interdiffusion fluxes. Expressions for internal consistency among the concentration profiles or flux profiles of the individual components were also developed in terms of the terminal alloy compositions and applied to the Cu-Ni-Zn couple in the diffusion zone. This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was held during TMS 2006, 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University.     

影响扩散的新因素

在进行工件渗硼试验中，发现了一种反常现象。渗碳后再进行渗硼，虽然工件表面含碳量大为增加，但渗硼速度不但不减，反而显著增大。此后又发现低温氮碳共渗亦能提高钢件的渗硼速度，更可贵的是氮碳共渗不仅能提高渗硼速度．而且还可以显著提高钢件渗金属的速度。     

Be Diffusion and Suppression in HBT StructureMaterials Grown by

ＢｅＤｉｆｆｕｓｉｏｎａｎｄＳｕｐｐｒｅｓｓｉｏｎｉｎＨＢＴＳｔｒｕｃｔｕｒｅＭａｔｅｒｉａｌｓＧｒｏｗｎｂｙＭＢＥＱｉｕＪｉａｎｈｕａ；ＬｕＹｏｎｇ；ＺｈｕＦｕｙｉｎｇａｎｄＬｉＡｉｚｈｅｎ（邱建华）（陆泳）（朱福英）（李爱珍）（ＳｈａｎｇｈａｉＩ...     

刹车片扩散焊性能试验

通过实验方法研究刹车片扩散焊焊接接头的性能,通过对相同式样在不同工艺条件下的试验,利用检测设备分别进行检测,采集相应式样的力学性能、扩散层显微组织状况和金属元素的扩散程度,经分析比较研究加热温度、压力与焊接性能的关系。总结出焊接接头实现了良好的冶金结合,其扩散层厚度较厚,剪切强度最高的工艺条件。     

扩渗时间对纯镁渗锌表面合金化的影响

对纯镁进行了表面渗锌处理，研究了400℃下扩渗时间对于合金化渗层组织、相结构及反应层连续性的影响。结果表明：扩渗温度为400℃时，随扩渗时间的延长，Zn扩散进入Mg基体表面的量和金属间化合物的生成量相应增加，晶界扩散优势得以削弱，最终使固溶层和反应层趋于均匀化。在此温度下，要形成连续的反应层，扩渗时间应为16h以上。