异种耐热钢瞬时液相扩散连接界面形态与形成机理

采用瞬时液相扩散连接双温工艺对异种耐热钢管进行了连接,使用氩气保护,FeNiCrSiB非晶箔作为扩散连接中间层.研究了异种耐热钢瞬时液相扩散连接界面的形成机理,测试了接头的组织和性能,采用激光共聚焦显微镜研究分析了界面形貌.结果表明,异种钢瞬时液相扩散连接时,液态中间层的结晶过程是在基体上联生生长,晶体长大具有方向性,少量杂质在接头中心以曲线状分布,形成了非直线型的连接界面.双温工艺的短时高温加热过程有利于破碎界面氧化物形成洁净连接晶面层,促进晶粒外延生长.     

陶瓷(玻璃)与金属基复合材料场致扩散连接机理研究

采用自行研制的静电键合机对固体电解质硼硅玻璃和β^ -氧化铝与铝基复合材料进行了静电场辅助的扩散连接试验。采用TEM、SEM、XRD等手段分析了结合界面微观结构。研究认为，结合区为金属-氧化物过渡区-陶瓷的结构形式，过渡区由表层过渡区和亚表层过渡区构成；连接过程主要包括静电键合和固相扩散接合两个阶段，界面离子聚集和迁移是产生阳极氧化和形成界面键合的主要机制，温度、电压和陶瓷(玻璃)的离子导电性是界面氧化物固相扩散接合的基本条件；电压、温度、压力及试件表面状态均为连接过程的主要影响因素。     

“INTERFACE WITHDRAWAL EFFECTS”AT TWOPHASE INTERFACES OF Cu:Cu-Al DIFFUSION COUPLES DURING QUENCHING

本文研究了淬火冷却过程中Cu:Cu-Al扩散偶α/β界面的逆向迁移,α/β界面的变温扩散模型在Fick第二定律基础上用数值分析法进行了计算.界面逆向迁移的距离和下列因素有关:高温时的原始浓度分布、扩散温度、扩散系数、冷却速率和相图中溶解度曲线的斜率.“界面逆向迁移效应”还影响了浓度分布曲线的形状和界面浓度.     

Cu:Cu-Al扩散偶淬火冷却过程中的“界面逆向迁移效应”

本文研究了淬火冷却过程中Cu:Cu-Al扩散偶α/β界面的逆向迁移,α/β界面的变温扩散模型在Fick第二定律基础上用数值分析法进行了计算.界面逆向迁移的距离和下列因素有关:高温时的原始浓度分布、扩散温度、扩散系数、冷却速率和相图中溶解度曲线的斜率.“界面逆向迁移效应”还影响了浓度分布曲线的形状和界面浓度.     

瞬间液相扩散焊过程中的接触熔化与等温凝固模型

接触熔化与等温凝固是瞬间液相扩散焊过程中两个非常重要的阶段,是获得优质连接接头的关键,一直以来也是学术界研究的热点.综述了接触熔化与等温凝固过程的动力学模型,包括接触熔化与等温凝固时间的解析解,接触熔化过程中反应层厚度与连接时间符合扩散控制的抛物线规则,以及等温凝固过程中液/固界面迁移的速度方程.并对现有模型进行了分析和讨论.     

陶瓷与金属扩散连接和场致扩散连接研究现状和进展

连接技术是材料加工和实际工程应用的热点内容,而扩散连接技术是实现陶瓷和金属可靠连接的主导方法之一.主要介绍了扩散连接的工艺、接头元素扩散与界面反应以及残余应力分析等,并在此基础上简介了场致扩散连接的工艺及其界面反应机理,突出了其温度低、时间短、压力小以及简便的工艺特点.     

电迁移促进Cu/Sn-58Bi/Cu焊点阳极界面Bi层形成的机理分析

研究了Cu/Sn-58Bi/Cu对接接头焊点在电流密度为5×103～1.2×104A/cm2条件下钎料基体中阳极界面Bi层的形成机理.电迁移过程中,Bi元素为主要的扩散迁移元素,在电迁移力的作用下由阴极向阳极进行迁移.由于Bi原子的扩散迁移速度比Sn原子要快,促使Bi原子首先到达阳极界面.大量的Bi原子聚集在阳极界面时,形成了压应力,迫使Sn原子向阴极进行迁移,于是在阳极界面处形成了连续的Bi层.阴极处由于金属原子的离去,形成了拉应力,导致了空洞和裂纹在界面处的形成.Bi层的形态主要分为平坦的Bi层和带有凹槽的Bi层.Bi原子进行扩散迁移的通道有三种:Bi晶界、Sn晶界和Sn/Bi界面.随着电流密度和通电时间的增加,Bi层的厚度逐渐增加.电迁移力和焦耳热的产生成为Bi原子扩散迁移的主要驱动力.     

合金激光表面熔凝组织的超塑扩散连接机理

研究了合金激光表面熔凝组织在超塑扩散连接中的细晶超塑变形和扩散机。对金属高温力学行为和晶界滑移微观机制的分析表明，激光表面改性获得的细晶组织，在连接过程中发生超塑变形，加速了空隙闭合；激光表面熔凝组织超塑扩散连接中出现了以晶界扩散为主的扩散模式，晶粒细化带来的晶界体积百分数的增加，提高了扩散速率；非平衡组织扩散性能以及非平衡晶界迁移加速了界面区空位、位错消除和再结晶过程。     

相变扩散连接界面生成金属间化合物的数值模拟

在异种材料扩散连接的接头中,当界面上有脆性的金属间化合物产生时,接头往往表现出较差的力学性能。因此,从扩散连接的生产应用及扩散连接的理论研究出发,研究扩散连接接头的界面金属间化合物的生成规律,进而对其控制,是有着非常重要的现实意义的。扩散连接界面上金属间化合物的生成及成长机制是受扩散控制的反应扩散机制,而相变扩散连接中往往还伴随着相变,因此相变扩散连接的界面反应机制更为复杂。本文根据相变扩散连接的     

TiB2金属陶瓷与TiAl金属间化合物的扩散连接

对TiB2金属陶瓷与TiAl金属间化合物进行了扩散连接试验，研究了直接扩散连接和采用Ni为中间层进行扩散连接的接头界面结构及工艺参数对界面结构和连接性能的影响。直接扩散连接时，连接界面处生成了Ti(Cu，Al)2金属间化合物，采用Ni为中间层进行扩散连接时，界面处生成了单层TiAlNi2金属间化合物层和两层T1，Al，N2扩散层共三层结构。直接扩散连接时，连接温度T＝1223K，时间t=1．8ks，压力p＝80MPa时接头强度为103MPa；采用Ni为中间层时，连接温度T＝1273K，时间t=1．8ks，压力p=80MPa时接头强度为110MPa。     

Effect of bonding temperatures on the transient liquid phase bonding of a directionally solidified Ni-based superalloy,GTD-111

The bonding phenomenon and the mechanism involved in the transient liquid phase bonding (TLP Bonding) of directionally solidified Ni-based superalloy GTD-111 was investigated. At a bonding temperature of 1403 K, the liquid insert metal was eliminated by isothermal solidification, which was controlled by the diffusion of B and Si into the base metal. The solids in the bonded interlayer simultaneously grew epitaxially from the mating base metal inward from the insert metal. The number of grain boundaries formed at the bonded interlayer corresponded with those of the base metal. Liquefaction at the grain boundary and dendrite boundary occurred at a temperature of 1433 K. At a bonding temperature of 1453 K which is higher than the liquefaction temperature of the grain boundary, liquids of the insert metal were connected with liquated grain boundaries; this connection extended as far as the grain boundary, which was approximately 1.5 mm from the interface. The composition of this liquid was a mixture of the insert metal and phase that existed at the grain boundary. At extended holding times, liquid phases gradually decreased, and liquids with a continuous band shape develop into distinct islands. However, the liquid phases did not disappear after a holding period of 7.2 ks at 1453K. The extended isothermal solidification process at the bonding temperature, which is higher than the liquefaction temperature for the grain boundary, was controlled by the diffusion of Ti. This resulted in its preferential liquefaction compared to B or Si in the insert metal.     

Be/HR-1不锈钢热静压高温形变的组织结构

利用光学金相显微镜、扫描电镜(SEM)、X射线衍射(XRD)仪和材料试验机分析Be/HR-1和Be/Cu/HR-1不锈钢真空热静压接头扩散区高温形变的组织结构和性能,探讨形变组织结构与压力和性能的关系.研究表明:热静压的作用使试样产生扩散性蠕变和晶界滑动,影响扩散焊区的晶粒大小和金属间化合物的数量;热静压应不得在使基体晶粒最大的临界压力或临界应变量下进行,适当降低压力和缩短时间可减少沿晶生成金属间化合物的数量,提高连接接头质量;Be/Cu/HR-1不锈钢热静压反应扩散生成的新相熔点大大低于原基材,适当降低温度或压力可有效控制连接工件的变形.     

INTERFACIAL ATOMIC-REACTION MODEL FOR DIFFUSION BONDING OF METALS

According to probability theory and atomic activation on bonding interface of metals,a mathematical model was developed for the atomic interfacial reaction during diffusionbonding.The effect of parameters of bonding processing and material on the bondingstrength was then gained.It was suggested that the activation centre of atomic interfacialreaction of bonding may be,in situ,the boundary dislocation and its elastic stress field.A substantial agreement about the quantitative prediction of the model was made withthe results of diffusion bonding experiments for 7075Al alloy     

Computer simulation of the reactive element effect in NiO grain boundaries

Diffusion within the grain boundaries of ceramics is an important mechanism for the growth of oxide films at moderate temperatures. Experiments show that the addition of impurities can drastically reduce the rate at which the film grows. We have investigated this by atomistic computer simulation. Since the migration energies of grain boundary processes in ionic systems are too high for a conventional molecular dynamics simulation to be used, we have used a modified simulation. The structure of the boundary is equilibrated and a vacancy introduced. A migration trajectory is chosen and a small force pulling the ion along this trajectory added to the ion that is to hop. A counter-force is added to the remaining ions to prevent the whole cell moving and the velocities are scaled to remove the energy introduced by doing work on the moving ion. The effect of this is to enable the hopping trajectory to be plotted out and the migration energy found. We have investigated the effect of Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ impurities on the migration energies and diffusion pathways of cation vacancies in the {310}/[001] and {410}/[001] tilt grain boundaries of NiO at moderate temperatures. We show that there is a correlation between the size of the impurity and its favoured position within the boundary. The presence of impurities increases the migration energies and alters the diffusion pathways. We conclude that impurities will bind vacancies to themselves, reducing the rate of diffusion.     

连接条件对00Cr25Ni7Mo3N双相不锈钢扩散连接的影响

利用热模拟试验机并结合扫描电镜(SEM)对00Cr25Ni7Mo3N超级双相不锈钢的超塑扩散连接进行实验研究,对不同连接条件下的孔洞形貌、界面组织进行相应的分析。研究结果表明,超塑性扩散连接试样的界面结合强度随扩散连接压力的增大、表面质量的提高及连接时间的延长而增大。扩散连接在连接温度1100℃时,连接压力为10MPa～20MPa;待连接表面经精磨处理后,连接时间10min～20min的条件下,可实现焊合率为96%～98%的扩散连接,且连接试样的初始连接界面消失,界面孔洞基本闭合,界面剪切结合强度达到407MPa～413MPa。     

Real time-temperature models for Monte Carlo simulations of normal grain growth

Two different models for the simulation of normal grain growth in metals and alloys are presented. These models demonstrate the application of real time-temperature based Monte Carlo (MC) simulation to materials processing. A Grain Boundary Migration model coupled the MC simulation to a first principle grain boundary migration model. The results of this simulation were shown to correlate well with the experimental results for isothermal grain growth in zone refined tin. An Experimental Data Based model coupled the MC simulation with experimental grain growth data. The results from this simulation were shown to correlate well with the grain growth during continuous heating of a beta titanium alloy.     

高强铜/钢双金属复合导板的界面结合机制

采用液态铜与钢复合、液态钢与铜复合两种方案制取了高强铜/钢双金属复合导板。对高强铜/钢双金属复合导板的界面处显微组织、元素分布进行了分析。结果表明,两种复合方式均可使高强铜/钢实现良好的冶金结合;在高强铜/钢双金属的复合过程中,原子优先沿金属表面扩散和晶间渗透,晶界是扩散的主要通道;高强铜/钢双金属界面结合主要通过表面润湿铺展和原子扩散导致富Fe和富Cu区形成Fe-Cu合金相等作用来共同实现。     

Laser cladding of titanium alloy coating on titanium aluminide alloy substrate

1　INTRODUCTIONInthedesignandmanufactureofaviationindus try ,differentpartsoftheaircraftengineshouldmeetthedifferentrequirementsonoperatingtemperatureandserviceperformance .Thesoundbondofdissimi laralloysisthekeytechniquefordevelopingnovele quipmentsandimprovingtheirintegralperformance .Lowdensityandexcellenthigh temperaturepropertiesofTiAlalloysmakethem promisinghigh temperaturestructuralmaterials .Successfuljoiningofthesematerialswillincreasetheirutilityinengineer ing[1,2 ] .Somejoinin…     

金属扩散焊接的原子反应模型

本文根据概率理论和金属扩散焊接过程中焊接面上原子激活的特点,建立了接合面上原子成键反应的数学模型,从而给出了焊接工艺参数和材料参数对接合强度的影响规律,模型中采用了界面上原子反应激活中心是界面位错及其弹性应力场的假设。文中以7075Al合金扩散焊接实验为基础,对模型进行了定量计算,计算结果与实验结果基本一致。     

Formation mechanisms of high quality diffusion bonded martensitic stainless steel joints

Abstract

Diffusion bonding of martensitic stainless steel was conducted at different times. Based on the interface characteristic and shear strength, bonding mechanisms were discussed. Results showed that the bonding quality was controlled by void shrinkage and interface grain boundary migration. Large voids with scraggly edges changed to small voids with smooth edges, leading to an increase in interface bonding ratio. Two cases of interface grain boundary migration were revealed: interface grain boundary migration at the triple junction induced by the reduction in grain boundary energy and strain induced interface grain boundary migration resulted from the stored energy. Owing to the void shrinkage and interface grain boundary migration, the shear strength of the joint matched that of the base material.