The mechanical properties and microstructures of copper and brass joints soldered with eutectic tin-bismuth solder

The mechanical properties and microstructures ofcopper and brass soldered with eutectic tin-bismuth solder have been determined and the joints examined using metallographic techniques. Joints made with copper were stronger than those made with brass. At the copper/solder interface a uniform layer 2m thick of Cu_5.2Sn₅ was formed and at the brass/solder interface a uniform layer 2 m thick of (Cu, Zn)_2.9Sn and an irregular layer 2 to 5m thick of (Cu, Zn)_5.7Sn₅ were formed. Copper joints fractured etthocopper/solder interface and brass joints fractured in the internmetalic layer. Copper joints soldered with eutectic Sn-Bi were stronger than copper joints soldered with eutectic Sn-Pb and the reverse was true for brass joints. Results are also given for the effect of thermal shock on copper and brass joints soldered with Sn-Bi and Sn-Pb solders, and also for We fatigue and creep behaviour of joints soldered with eutectic Sn-Bi solder.     

Preparation of the Sb-containing purple conversion coating on brass

A new chemical method for preparing a purple conversion coating on brass was developed. The effect of antimonous oxide concentration and temperature on color and corrosion resistance of the conversion coating, and the change of electric potential with time on coating forming process were studied. The optimum technological conditions were 10?g/L antimonous oxide, 20?g/L copper acetate, 200?mL/L hydrochloric acid at 65°C for 3?min. Results of electrochemical and dropping experiments showed that the brass with purple conversion coating presents better corrosion resistance than bare brass. The scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) results showed that the conversion coating mainly comprising copper and antimony was uniform and compact.     

Ultrasonic characterization of the effect of cold work and grain size in copper and 68:32 brass sheets

The effectiveness of ultrasonic velocity measurements was evaluated as a means for nondestructive characterization of cold-rolled copper and 68:32 brass sheets. An apparatus was designed to generate and receive the zeroth symmetrical mode of ultrasonic Lamb waves in thin copper and brass sheets. The effect of angular variations in propagation direction with respect to the rolling direction on the measured Lamb wave velocities is shown. Interpretation of the variations of ultrasonic Lamb wave velocity were related to deformation mechanisms and texture development in copper and 68:32 brass sheets. Results show that the grain size and cold work influence the velocity as well as the texture of copper and 68:32 brass sheets. Results indicate the possibility of using ultrasonic Lamb wave velocity as a tool to monitor elastic anisotropy.     

Effect of Columnar Grain Orientation on Ultrasonic Plane Wave Energy Reflection and Transmission Behaviour in Anisotropic Austenitic Weld Materials

This article describes a comprehensive quantitative analysis on effect of columnar grain orientation on ultrasonic plane wave energy reflection and transmission behaviour in acoustically anisotropic austenitic weld materials. The quantitative results are presented for following general interfaces (a) Isotropic-Anisotropic, (b) Anisotropic-Isotropic, (c) Fluid-Anisotropic, (d) Anisotropic-Fluid, (e) Anisotropic-Anisotropic, (f) Anisotropic-Free surface occur during the ultrasonic non destructive evaluation of austenitic weld materials. Explicit analytical expressions are presented for energy reflection and transmission coefficients at an interface between two arbitrarily oriented transversely isotropic materials. By applying explicit analytical expressions for energy reflection and transmission coefficients, numerical results are presented for several columnar grain orientations of the transverse isotropic austenitic weld material including both real and complex domain of the reflected and transmitted normal component of slowness vectors. Valid domains of incident wave vector angles, angular dependency of energy reflection and transmission coefficients and critical angles for reflected and transmitted waves are discussed. The existence of a reflected (or) transmitted second branch of quasi shear vertical waves and its consequence to the ultrasonic non destructive testing of austenitic weld materials are investigated. The presented comprehensive quantitative evaluation provides an overview on the effect of anisotropic properties on energy reflection and transmission coefficients in columnar grained austenitic weld materials.     

The shear strength of copper and brass soldered with Sn-40% Pb containing 0 to 10% Sb and/or 0 to 15% Zn

The single lap shear strength of copper and brass soldered with Sn-40% Pb containing 0 to 10% Sb and/or 0 to 15% Zn has been determined and the microstructure examined using metallographic techniques. For any solder composition, brass joints were stronger than copper joints. The strength of copper joints decreased monotonically with the increase of antimony in Sn-Pb solder, and the strength of brass joints increased to a peak with about 3% Sb in the solder and thereafter decreased on further additions of antimony. With less than a few per cent antimony in the solder, 1 % Zn in the solder decreased the strength of both copper and brass joints; with more than 1 % Zn in the solder the strengths of both copper and brass joints were increased substantially. Fracture occurs mainly in the Cu₆Sn₅. The microstructure and the presence of zinc in the intermetallic compounds were determined, and the results are discussed.     

Microstructure development during dissimilar welding: Case of laser welding of Ti with Ni involving intermetallic phase formation

Development of solidification microstructure in a laser welded Ti/Ni dissimilar binary couple is presented. At the fusion interfaces in both Ti and Ni, growth of the base metal grains into the weld pool is inhibited by the presence of composition gradients in the melt. Ti₂Ni dendrites grow toward the base metal at the Ti fusion interface. In the Ni side, appearance of a nickel solid solution phase is followed by layers of Ni₃Ti, Ni₃Ti+NiTi eutectic, and NiTi. NiTi dendrites and Ti₂Ni constitute the microstructure in the middle of the weld. Isolated titanium dendrites are observed throughout the weld, but their preferential occurrence toward the top surface of the weld is more prominent. Results are rationalised on the basis of interplay of the transport processes in the weld with the thermodynamics of the Ti-Ni system.     

Elemental fractionation studies in laser ablation inductively coupled plasma mass spectrometry on laser-induced brass aerosols

Previous investigations on laser-induced aerosols of brass samples showed that preferential vaporization of zinc occurs during the ablation process leading to elemental fractionation and limited possibilities for non matrix matched calibration. In a variety of experiments carried out within this study it is shown that multiple effects are complicating the quantification of brass using IA-ICPMS. It is shown that the ablated copper and zinc is not homogeneously distributed within the laser-produced aerosol. Copper was found enriched up to 100% in particles larger than 100 nm as shown from EDX measurements (electron excited) on individual particles, and zinc was enriched by over 40% in the particles smaller than the lowest measurable particle size (below 100 nm or in the vapor phase). Solution nebulization analysis on digested filter-collected aerosols results in a higher Cu/Zn ratio than the certified value for the brass sample. ESEM pictures with analysis of the electron excited X-rays measured on the filter-collected material support the results showing copper enrichment. However, online LA-ICPMS measurements carried out under the same operating conditions as for filtering show a copper depletion within the ICP, which leads to the conclusion of partial vaporization and ionization of the aerosol particles in the ICP. The larger particles containing more or exclusively copper are not completely ionized. Within this study, three sources of elemental fractionation can be distinguished and described: (A) The ablation process leads to no measurable copper enrichment at the ablation crater rim. (B) Zinc deposition between the ablation site and the aerosol collection on filters leads to an up to 37% higher Cu/Zn ratio on the filter in comparison to the certified value. (C) On-line laser ablation aerosols measured within the ICPMS lead to significantly lower Cu/Zn ratios in comparison to the certified value. (D) Combination of the various studied sources of fractionation can finally lead to an agreement between measured and certified values due to inverse overlapping of various fractionation sources.     

铝-铜爆炸焊块补焊试验研究

研究了铝-铜爆炸焊块铜面缺陷修补的焊接工艺,针对不同部位的铜面缺陷,探讨了焊接热输入对铝-铜爆炸焊块界面结合强度的影响,确定了允许修补的缺陷范围。     

Microstructures and mechanical properties of friction stir welded dissimilar copper/brass joints

In this study, an experimental investigation has been carried out on microstructure and mechanical properties of friction stir welded copper/brass dissimilar joints. Effect of axial tool force to welding quality has been investigated under obtained optimal tool rotation rate and tool traverse speed conditions. The tool for the dissimilar copper/brass friction stir welding manufactured from X155CrMoV12–1 cold work tool steel with material number of 1.2379. The friction stir welding quality was investigated by welding surface inspections, microstructural studies, micro hardness measurements and tensile tests. The experimental studies have shown that constant axial tool force during pre‐heating and during welding process are very important. As a result, by using 2.5–3 kN of axial tool force during pre‐heating and 5.5 kN of axial tool force during welding process, copper/brass dissimilar joints with well appearance and higher mechanical strength can be obtained.     

A comparative analysis of copper and brass surface films in contact with tap water

A study of the surface oxide films naturally grown on copper and brass in contact with drinkable water is presented. The investigation focuses on the influence of Zn as alloying element on the corrosion resistance of brass. Artificial tap water, employed as electrolyte, simulates a practical application of these materials. The surface films were grown at open circuit potential for 2 and 192 hours. Diverse in-situ techniques such as cyclic voltammetry, polarization curves, electrochemical impedance spectroscopy and UV-Vis reflectance spectroscopy were employed. Even when the surface layer is mainly composed of cuprous oxide, Zn(II) species are incorporated in the surface film grown on brass. At longer ageing times, the thickness increases, without affecting the composition of the surface films. The corrosion current was calculated for both materials using various techniques. The corrosion current density and the anodic currents in the polarization curves decreased as the ageing time increased, particularly in the case of brass. This improvement in the performance of the film on brass can be attributed to the incorporation of Zn(II) species into the surface layer, particularly as the film consolidates at longer times.     

Thermal stability of shielding effectiveness of electromagnetic interference of composites

A series of composites were prepared using polyethylene and various chatter-machined metal fibres (aluminium, copper, steel and brass) and carbon fibre, and the effects of the concentration of the fillers and the thermal treatment of the composites at 80° C in air on the shielding effectiveness (SE) of eleotronnagnotic interference were examined. The order of the generation of SE was, brass > steel > copper aluminium > carbon. Thermal degradation of SE was scarcely observed in the carbon fibre system and very slightly in the brass and steel systems, while remarkable degradation was observed in the copper and aluminium systems. This degradation was assumed to be due to the formation of an oxidized surface to increase the contact resistance between fillers. Stabilization of the thermal degradation of SE of the aluminium composite was possible to some extent when the aluminium surface was pretreated with certain reagents.     

火力发电厂凝汽器铜管的腐蚀与防护

介绍了火力发电厂凝汽器铜管在使用寿命期间的腐蚀状况,指出黄铜管的腐蚀主要表现为脱锌腐蚀、应力腐蚀开裂和冲蚀等,分析讨论了其各自的腐蚀机理及相应的控制措施,介绍了铜管主要保护方法--硫酸亚铁成膜技术,对控制电厂铜管腐蚀提供一定的参考.     

Grain Size Measurement of Copper Spot Welding Caps Via Ultrasonic Attenuation and Scattering Experiments

During ultrasonic testing of resistance spot welds in real time, the probe sends the sound waves through the thickness of the copper electrode cap into the materials being welded. Characteristics of the reflected waves from the weld interfaces allow a reliable decision to be made on the quality of the joint. Transmission of high frequency sound waves through the relatively thick copper welding cap cause the signal to be greatly attenuated due to grain scattering. For this reason, close monitoring of the copper cap properties prior to installation is essential for adequate performance. Finding copper alloys with a small average grain size is essential in order to minimize the attenuating effects. The conducted backscatter and attenuation experiments indicate correlation between the ultrasonically measured parameters and the optically found copper grain size. This correlation suggests that the attenuation or backscatter technique could be used alone in order to validate the proper copper alloy to be used in spot weld probes. Using nondestructive testing techniques for this purpose greatly reduces the time and cost involved compared to optical techniques.     

铜和铝作为钛-钢爆炸焊接夹层时的复合工艺及焊接界面的实验研究

文章介绍了铜、铝作为钛 -钢爆炸焊接夹层时的复合工艺 ,并对实验中的各种界面进行了超声探伤、扫描电镜及能谱分析。认为与铝相比铜更适合于作钛 -钢爆炸焊接的中间夹层。     

Fracture of a ductile layer constrained by stiff substrates

A combined experimental and theoretical analysis of the fracture behaviour of brass/solder/brass sandwich specimens is conducted. First, the theories of interfacial fracture initiation for a ductile layer sandwiched between elastic substrates are reviewed. The fracture behaviours are then reported of brass/solder/brass sandwich specimens under various mode mixities. Additionally, the effects of solder layer thickness h and specimen lateral thickness t are presented. The effects of mode mix and plastic constraint on the failure mechanism and toughness are analysed.     

Failure mode and interface chemistry of localized coatings on brass

The behaviour of partly coated aluminium brass has been examined under accelerated laboratory and under natural conditions. Acrylic (Incralac) coatings are found to have a good life and to provide a long-term protection of brass surfaces. Analysis of failed interfaces by photoelectron spectroscopy showed that acidic conditions developed beneath the coating and contributed to a partial weakening of the bond strength. Eventually the crevice conditions drift back towards neutral and there is little further loss of strength.     

DETERMINATION OF STRESS CORROSION CRACK INITIATION STRESS AND CRACK VELOCITIES USING SLOWLY STRAINED TAPERED SPECIMENS

Abstract— Previous work has shown that a single tapered cylindrical specimen subjected to slow strain rate testing can provide data for the crack initiation stress of 70/30 brass in 1N NaNO₂ solution. In order to test the wider applicability of that technique, crack initiation stresses of a further five systems were measured. These were 70/30 brass in an ammoniacal solution, copper in sodium nitrite and mild steel in carbonate–bicarbonate, hydroxide or nitrate solutions. The results are compared with those obtained from tests on plain cylindrical specimens subjected to interrupted slow strain rate tests or to constant load tests, and the agreement is reasonable. The method also is capable of providing data on the stress dependence of crack velocities.     

Neural classification of Lamb wave ultrasonic weld testing signalsusing wavelet coefficients

This paper presents an ultrasonic nondestructive weld testing method based on the wavelet transform (WT) of inspection signals and their classification by a neural network (NN). The use of Lamb waves generated by an electromagnetic acoustic transducer (EMAT) as a probe allows us to test metallic welds. In this work, the case of an aluminum weld is treated. The feature extraction is made by using a method of analysis based on the WT of the ultrasonic testing signals; a classification process of the features based on a neural classifier to interpret the results in terms of weld quality concludes the process. The aim of this complete process of analysis and classification of the testing ultrasonic signals is to lead to an automated system of weld or structure testing. Results of real-world ultrasonic Lamb wave signal analysis and classifications for an aluminum weld are presented; these demonstrate the feasibility and efficiency of the proposed method     

Atom probe tomography characterization of solute segregation to dislocations and interfaces

The level and extent of solute segregation to individual dislocations and interfaces may be visualized and quantified by atom probe tomography. The large volume of analysis and high data acquisition rate of the local electrode atom probe (LEAP^®) enables the solute distribution in the region of and along the core of dislocations to be estimated. Solute segregation at precipitate-matrix interfaces of precipitates as small as 2-nm diameter may be quantified. Examples are presented of solute segregation to dislocations and clustering/precipitation in a neutron irradiated Fe–Ni–P model alloy and the neutron irradiated beltline weld from the Midland reactor.     

Friction Stir Weldabilities of AA1050-H24 and AA6061-T6 Aluminum Alloys

The friction stir weldabilities of the strain-hardened AA1050-H24 and precipitate-hardened AA6061-T6 aluminum alloys were examined to reveal the effects of material properties on the friction stir welding behavior. The experimental results are obtlained. (1) For AA1050-H24, the weld can possess smoother surface ripples; there is no elliptical weld nugget in the weld; there is no discernible interface between the stir zone and the thermomechanically affected zone; and the internal defect of the weld looks like a long crack and is located in the lower part of the weld. (2) For AA6061-T6, the weld usually possesses slightly rougher surface ripples; an elliptical weld nugget clearly exists in the weld; there are discernible interfaces among the weld nugget, thermomechanically affected zone and heat affected zone; and the internal defect of the weld is similar to that of the AA1050-H24 weld. (3) The effective range of welding parameters for AA1050-H24 is narrow, while the one for AA6061-T6 is very wide. (4) T