熔池形态对铝-铜激光焊接头组织和性能的影响

对T2紫铜板、2A16铝合金板进行激光熔化焊和熔钎焊试验,分析接头的力学性能,并研究其微观组织及界面形貌,阐述熔池形态对接头组织和性能的影响.结果表明:采用激光熔化焊时得到熔化焊熔池,当焊接线能量Q=1160 J/cm时,其界面层由Al4 Cu9+Al2 Cu化合物和(α-Al)+(θ-Al2 Cu)共晶组织组成,总厚度为60.9μm.采用激光熔钎焊时得到熔钎焊熔池,当Q=1466.67 J/cm时,接头抗拉强度为274.25 MPa,相比熔化焊接头提高了280.9％,其界面层由CuZn5和Al2 Cu化合物组成,总厚度为10.23μm.接头接触界面的互扩散系数(D熔化焊>D熔钎焊)和不同熔池形态下的环形对流共同影响了IMC层厚度,从而决定了接头的性能.     

Sn8Zn3Bi-xCu/Cu焊接接头界面反应及力学性能研究

以Sn8Zn3Bi为研究对象,采用微合金化方法研究了不同含量的Cu元素对其显微组织、钎料合金与Cu基板钎焊后的界面金属间化合物(IMC)层尺寸及焊接接头剪切强度的影响。结果表明,Sn8Zn3Bi-xCu/Cu(x=0.3,0.5,0.8,1.0,1.5)焊接界面IMC主要为层状Cu5Zn8相。随着Cu含量的增加,界面IMC层的厚度逐渐减小,接头的剪切强度逐渐提高,Sn8Zn3Bi-1.5Cu/Cu接头剪切强度较Sn8Zn3Bi/Cu显著提高。经120℃时效处理后,Sn8Zn3BixCu/Cu(x=0,0.3,0.5,0.8,1.0,1.5)焊接接头剪切强度都明显下降,接头断裂方式由韧性断裂转为局部脆性断裂,但添加了Cu元素的钎料界面IMC生长速度较Sn8Zn3Bi钎料慢,因此Cu元素的添加抑制了界面IMC层的生长。     

添加SiO2纳米粉末AC辅助Al/Cu等离子弧熔钎焊接头组织及性能分析

从工艺方法改进和界面调控方面提出了添加SiO₂纳米粉末AC辅助Al/Cu等离子弧熔钎焊,实现了成形及力学性能良好的Al/Cu异种金属接头,并对界面处微观组织及接头力学性能进行了对应分析,对其界面形成的内在机理进行相应阐述。结果表明,AC辅助电弧的引入可显著改善Al在Cu母材表面的润湿铺展性能,接头有效连接长度由12.25 mm增加至15.2 mm;接头微观组织分析表明,纳米SiO₂吸附于Cu界面及IMC层,起到了扩散阻挡作用,阻碍了Al和Cu原子的反应和相互扩散,减小了焊接过程中界面IMC的厚度,减缓了等温时效过程中IMC的生长。同时,较大的有效连接长度和对IMC层的抑制作用使添加SiO₂纳米颗粒AC辅助电流值为45 A的接头断裂承受最大载荷为0.85 kN,断裂位置位于铝侧热影响区,接头力学性能较好。     

水下搅拌摩擦焊对铝/铜接头组织与性能的影响

目的 采用搅拌摩擦焊,对比分析大气环境和水下环境下铝/铜接头的组织与性能,以期获得力学性能更优异的铝/铜焊接接头。方法 利用搅拌摩擦焊,在焊接速度为40 mm/min、旋转速度为1 000 r/min的条件下,分别在大气环境和水下环境下对厚度为9 mm的6061铝合金板和T2纯铜板进行焊接。然后,对铝/铜界面、焊核区进行扫描电镜及能谱分析,并对铝/铜界面及焊核区进行物相分析,确定产物相组成。最后,对铝/铜试样进行拉伸及硬度检测。结果 铝/铜接头均无裂纹、气孔等缺陷。铜颗粒弥散分布在焊核区,铝/铜界面形成金属间化合物层。水下搅拌摩擦焊下界面元素扩散距离明显变短,且金属间化合物厚度更薄。铝/铜接头的金属间化合物为AlCu和Al4Cu9。大气环境焊接下接头的抗拉强度为130.6 MPa,断裂方式为脆性断裂;水下焊接下接头的抗拉强度为199.5 MPa,断裂方式为韧性断裂。水下环境下的接头硬度值更高,其中热影响区的硬度最低值约为65HV。结论 水下搅拌摩擦焊铝/铜接头无裂纹、气孔等缺陷。组织上,水下搅拌摩擦焊的铝/铜接头界面元素扩散距离更短,硬脆的金属间化合物更少;性能上,水下搅拌摩擦焊的铝/铜接头强度更高,抗拉强度达到199.5 MPa,达到母材的74.4%。     

利用金属间化合物增强陶瓷钎焊接头 --接头组织与界面反应

为了提高Si3N4陶瓷连接接头高温性能及减小接头因热膨胀系数不匹配而产生的应力,采用Ag-Cu-Ti钎料和NiTi复合中间层进行半固态连接.接头组织观察表明,钎缝主要由NiTi(Cu)金属间化合物和Ag-Cu基体组成.研究表明,Ni与Ti的加入量对于钎缝中金属间化合物的形态及钎缝与母材界面反应层的形成具有十分重要的影响.     

激光钎焊Sn-0.7Cu/Cu界面IMC生长行为EI北大核心

金属间化合物IMC厚度及形貌对焊点力学性能起到关键作用。本工作以激光为加热热源,Cu为基底,研究钎焊时激光功率以及激光扫描速度对Sn-0.7Cu无铅焊料界面金属间化合物生长规律的影响。结果表明:不同激光参数下,得到的界面金属间化合物形貌及厚度存在差异。随着激光功率增大,界面处形成的Cu6Sn5IMC层变厚;而随着扫描速度增大,IMC厚度减小;界面IMC厚度变化与功率及扫描速度有如下函数关系:d=D0+Kp/v。     

Al/Cu键合系统中金属间化合物的形成规律及防止方法

Al/Cu键合界面金属间化合物的形成是导致微电子器件失效的重要因素之一,总结了微电子器件生产和使用过程中Al/Cu键合界面金属间化合物的生长规律,分析了Al/Cu键合系统的失效机制。热超声键合过程中,Al焊盘上氧化铝层的破裂使金属间化合物的形成成为可能,键合及器件使用过程中,金属间化合物和柯肯德尔空洞的形成和长大最终导致键合失效。采用在Al焊盘上镀覆Ti过渡层的方法,可有效降低键合系统中Cu原子的扩散速度,抑制金属间化合物的生长,从而提高电子元器件的可靠性。     

固溶处理冷却方式对Cu/Al复合板界面微观组织的影响

利用光学显微镜、扫描电镜、X射线衍射等手段研究了冷却方式(水冷、空冷和炉冷)对Cu/Al复合板界面微观组织的影响,利用显微硬度仪测试了冷却方式对铸轧Cu/Al复合板力学性能的影响。实验结果表明:铸轧复合板界面形成Al_2Cu、AlCu、Cu_9Al_4、AlCu_3四种金属间化合物,经500℃×2 h固溶处理后,界面扩散层厚度增加,形成Al_2Cu、AlCu、Al_2Cu_3、Cu_9Al_4、AlCu_3五种金属间化合物。水冷和空冷界面扩散层产生孔洞,炉冷孔洞基本消失,解释了孔洞形成原因及变化过程,孔洞等缺陷会削弱界面层的结合强度。铸轧复合板界面扩散层厚度小、硬度低;经固溶处理后,界面扩散层厚度和硬度均增加,并随冷却速度的减小,厚度和硬度进一步增加。剥离过程中,铸轧复合板靠近Al基体断裂,而经固溶处理后的复合板断裂在界面扩散层。随冷却速度的下降,裂纹扩展能力减弱,过厚的金属间化合物不利于复合板的结合。     

热处理对冷轧铜铝复合板材界面扩散层结构的影响

用SEM、TEM、微区XRD等手段分析了复合板界面扩散层的形貌和结构,研究了热处理工艺对冷轧铜铝复合板材界面扩散层结构的影响,讨论界面扩散层形成规律。研究表明,冷轧铜铝复合板经过扩散热处理后,在复合界面形成具有扩散性质的界面层,随着热处理时间的延续,界面扩散层由最初的单层逐渐生长为三层,进一步延长热处理时间,界面层的层数不变,厚度略有增加;界面层含有q(Al2Cu)相、h2(AlCu)相和g2(Al4Cu9)相等金属间化合物;界面扩散层结构为:铝侧的Al-Cu固溶体与q(Al2Cu)相复合层、h2(AlCu)相层和铜侧的Cu-Al固溶体与g2(Al4Cu9)相复合层。     

热循环对SnAgCu(纳米Al)/Cu焊点界面与性能影响

研究了纳米0.1%(质量分数)Al颗粒对SnAgCu无铅钎料与铜基板之间界面反应的影响,研究两种无铅钎料界面在-55~125℃热循环过程中的生长行为及其焊点力学性能变化。结果表明:随着热循环次数的增加,界面层金属间化合物的厚度明显增加,焊后界面层金属间化合物为Cu6Sn5相,在热循环过程中在Cu6Sn5和Cu基板之间出现Cu3Sn相。发现纳米Al颗粒的添加,界面层金属间化合物的厚度明显减少,纳米颗粒对界面层的生长具有明显的抑制作用。同时对焊点在热循环过程中的可靠性进行分析,发现焊点的拉伸力随着循环次数的增加逐渐降低,含纳米Al颗粒的焊点具有明显的优越性,在焊点服役期间,焊点失效路径为Cu6Sn5/Cu3Sn的界面处。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。