Pb-Sn Alloys Research Articles

Enhanced Hydrogen Generation from Magnesium-Aluminum Scrap Ball Milled with Low Melting Point Solder Alloy.

In this investigation, composite materials were manufactured of mixed scrap of Mg-based alloys and low melting point Sn-Pb eutectic by high energy ball milling, and their hydrogen generation performance was tested in NaCl solution. The effects of the ball milling duration and additive content on their microstructure and reactivity were investigated. Scanning electron microscopy (SEM) analysis indicated notable structural transformations of the particles during ball milling, and X-ray diffraction analysis (XRD) proved the formation of new intermetallic phases Mg2Sn and Mg2Pb, which were aimed to augment galvanic corrosion of the base metal. The dependency of the material's reactivity on the activation time and additive content occurred to be non-monotonic. For all tested samples ball milling during the 1 h provided, the highest hydrogen generation rates and yields as compared to 0.5 and 2 h and compositions with 5 wt.% of the Sn-Pb alloy, demonstrated higher reactivity than those with 0, 2.5, and 10 wt.%.

Effect of Al and Bi addition on the corrosion behaviour, hardness, and melting temperature of lead-free solder alloys

Herein, the influence of alloying bismuth (Bi) and aluminum (Al) on the corrosion performance of Sn9Zn in a 3.5 % NaCl solution was examined. Electrochemical techniques were used to examine the corrosion behaviour of Sn9Zn, Sn-9Zn-0.5Bi, and Sn-9Zn-0.5Bi-0.5Al. After corrosion measurements, the alloy surfaces were studied by scanning electron microscopy (SEM) and energy dispersive X-ray diffraction (EDX). The results demonstrated that the presence of Bi increased the corrosion resistance because it formed an anodic barrier on the Sn-9Zn-0.5Bi alloy surface. The study extended to measure the Vickers hardness number of these alloys, and the results indicated a significant improvement in the hardness number of the Sn9Zn alloy by approximately 11 % with Bi and 54 % with Bi and Al. More investigations of the melting temperature behaviour of solder alloys using differential scanning calorimetry (DSC) were also carried out before corrosion measurements. The DSC results demonstrated that Sn-9Zn-0.5Bi-0.5Al had a lower melting temperature than Sn9Zn and Sn-9Zn-0.5Bi. Therefore, Al and Bi addition improved the melting temperature characteristics of the Sn9Zn solder alloy. This confirmed that the presence of Bi only enhanced the corrosion resistance, and the presence of both Bi and Al played a crucial role in the properties enhancement of the Sn9Zn alloy. Consequently, these improved characteristics and properties make the suggested compositions a significant alternative choice to SnPb alloys.

Multiple process microstructure evolution simulation of ultrasonic assisted rolling directed energy deposition

Directed energy deposition (DED) has a widely application prospect, but dendrite and component segregation are not easily controlled and predicted. In this study, the method of applying ultrasonic assisted rolling was introduced to the DED to eliminate above phenomenon. A multiple process microstructure evolution simulation (involved melting, solidification, dynamitic recrystallization and grain growth) was also carried out, which introduced ultrasonic effect in the form of energy. The influence of ultrasonic amplitude (A), distance between laser focus point and ultrasonic roller (d0) on microstructure of Pb-Sn alloy deposition layer were explored. There is a good consistency between experiment and simulation with relative error of 4.33%. The results show that the roundness of grains is improved significantly after rolling, and the grain are refined with the increase of A and d0. In all tests of this study, comprehensive effect of ultrasonic rolling achieves the best when d0 is taken as 24 mm and A is taken as 20 μm, the average grain diameter (D0) in grain size counted zone is 18.8 μm which is 23.23% lower than that without rolling. This study laid a foundation for the development of ultrasonic assisted rolling DED and provide a multiple process microstructure simulation method.

Constructing of Pb–Sn/α-PbO2/β-PbO2-Co2MnO4 composite electrode for enhanced oxygen evolution and zinc electrowinning

Developing a highly efficient and stable electrode for oxygen evolution reaction (OER) in harsh conditions (∼1.63 M H2SO4) is desirable but still challenging. Herein, the paper describes Co2MnO4 modifying β-PbO2 (Pb–Sn/α-PbO2/β-PbO2-Co2MnO4) via thermal decomposition and subsequent electrodeposition. Consequently, the synthesized electrode presents a layer structure, where Pb–Sn alloy serves as the matrix, α-PbO2 functions as mid-layer to enhance the binding force between the matrix and β-PbO2, and β-PbO2-Co2MnO4 acts as active layer for OER. In addition, the obtained quasi–three–dimensional Pb–Sn/α-PbO2/β-PbO2-Co2MnO4 electrode exhibits the lowest overpotential of 571 mV for 50 mA cm−2 and a small Tafel slope of 207.1 mV dec−1 in 1.63 M H2SO4 electrolyte. Moreover, it shows the smallest corrosion rate of 0.13 mg cm−2 h−1 and the longest accelerated service life of 59 h at 2 A cm−2. Furthermore, it is used as an anode for zinc electrowinning, in which the cell voltage and power consumption for producing one–ton zinc are lower by 230 mV and 304.2 kW h as compared with the benchmark electrode of Pb-0.76%Ag alloy. Hence, this paper provides the strategy to design and construct non-precious, high–performance catalysts for electrolysis and other applications.

Pulsed and Static Magnetic Field Influence on Metallic Alloys during Solidification

Electromagnetic methods can be used to affect the solidification of metallic alloys. Combined alternating and static (DC) magnetic fields can induce pressure waves in liquid metals in a contactless manner, refining grain structure, preventing component segregation, and dispersing added particles. Here, the possibility of using a pulsed magnetic field in combination with a DC magnetic field to improve the solidification structure of metals is investigated. This enables achieving higher pressure amplitude and liquid movement within the whole crucible volume at the same power consumption. This can be a prospective way to achieve a fine-grained and a more homogeneous microstructure of metallic alloys as well as disperse added particles. In this work, analytical description of the phenomena and numerical modeling of the pressure amplitude and melt motion has been performed. A series of experiments have been carried out to demonstrate the effect of such interaction on the solidified metal microstructure. It is found that a combination of pulsed and DC magnetic fields creates strong compression and expansion of the liquid metal. Metals solidified under such interaction exhibit finer grain structure in Sn-Pb alloy and improved TiB2 particle distribution in 6061 aluminum alloy.

Modeling and measurement of vapor-liquid equilibrium of In–Pb and In–Pb–Sn alloy systems in vacuum distillation

This study reports the measurement and modeling of vapor-liquid equilibrium (VLE) in In–Pb and In–Pb–Sn alloys subjected to vacuum distillation at a system pressure of 5–10 Pa in the temperature range of 1100–1280 K. Pb and In was satisfactorily separated by a single-stage distillation at 1180 K. Pb was thoroughly removed from In–Pb–Sn alloy by a single-stage distillation at 1220 K. Molecular interaction volume model (MIVM) was used to calculate the activities of components of In–Pb alloy. The deviations were small. The activities of components of In–Pb–Sn alloy were also predicted by MIVM. The VLE of In–Pb and In–Pb–Sn alloy systems were predicted by MIVM and VLE theory. The calculated results agree well with VLE data determined from experiments, which indicates that the calculated VLE is reliable. The VLE can be used to guide the separation of indium-based alloys by vacuum distillation. In this study, the model prediction was combined with vacuum distillation experiments, which not only verified the reliability of MIVM for indium-based alloys, but also optimized the process parameters of vacuum distillation of indium-based alloys, providing theoretical guidance for the separation and purification of indium-based alloys by vacuum distillation or the treatment of indium-containing complex materials.

Three-dimensional numerical analysis and experimental confirmation for investigating the ground-based lateral droplet ejection toward microgravity simulation

Rapid in situ manufacturing is significant in space exploration. Droplet-based printing technology with micrometer accuracy has great potential in space due to the advantages of convenient transportation, customized metal material, and good environmental adaptability. It could achieve the ground microgravity simulation by a small Bond number (Bo < 1). The present work proposes a new method to evaluate the reliability of the ground microgravity simulation in the lateral metallic droplet-based ejection. The three-dimensional model is developed to numerically analyze the droplet ejection dynamic process coupled with the volume of fluid method and the k–ω shear stress transport model. The model accuracy and efficiency are improved by the local fine grid. In addition, the computation is validated by the cryogenic alloy droplet ejection experiments and theoretical analysis. The proposed theoretical analysis equation has good agreement with the SnPb alloy droplet ejection trajectory. Reynolds number (Re), Weber number (We), Froude number (Fr), Ohnesorge number (Oh), and breakup length (Lb) are used to analyze the gravity influences on the droplet ejection process of different materials, nozzle length–diameter ratios, and crucible fluid unfilled heights. The ejection direction has little effect on the aluminum droplet formation time and breakup length and the gravity effect increases with the length–diameter ratio and unfilled heights. In simulated results, the minimum We number of the aluminum droplet formation is 0.22 and the cryogenic alloy droplet formation is 0.19. The reliability of ground physical microgravity simulation is dependent on material selection, and aluminum is more suitable than the cryogenic and SnPb alloys.

Development and benchmarking of numerical model in OpenFOAM® for the prediction of channel segregation during columnar alloy solidification

• Benchmark sn-5 wt%Pb alloy solidification problem is simulated using OpenFOAM solver. • Mesh sensitivity analysis is performed to resolve the flow in channels segregates. • Effect of microsegregation and mushy zone models on channels formation is studied. • Scheil's model predicts more negative and positive segregation than Lever rule. • Inertial drag in mushy zone significantly affects the channel segregates formation. In the past, most of the numerical studies on the prediction of macrosegregation and mesosegregation (e.g. channel type segregation) were performed using in-house codes and commercial software, both of which have limitations such as huge license costs, non-availability for general public research etc. In this study, a dedicated CFD solver is developed in an open-source platform – OpenFOAM® for the prediction and characterization of channel segregates in castings. The solver accounts for the fluid flow, heat transfer, species transport, multiscale segregation, solidification and mushy zone drag phenomena that occur during alloy solidification. The developed solver is extensively validated with the reported benchmarked experimental and numerical results for the sn-Pb alloy solidification. Direct numerical simulations (DNS) are performed to resolve the flow field in and around the channels (which are of mesoscopic length scale) for the first time. It is observed that mesh size ≤ 2 d 2 (secondary dendritic arm spacing) is required to resolve the flow in channels and accurately predict their morphology and locations. Further, the effect of different microsegregation and mushy zone drag models on the segregation and morphology of channel segregates is thoroughly investigated. The predicted extent of negative and positive segregation is found to be more (negative segregation ∼ 7.7 wt%Pb and positive segregation ∼ 18.7 wt%Pb) in Scheil’s microsegregation model compared to Lever rule. Furthermore, the inertial drag in the mushy zone significantly affects the convective transport of solute and thereby the morphology and the number of channel segregates.

Enhanced Separation Behavior of Metals from Simulated Printed Circuit Boards by Supergravity

Printed circuit boards (PCBs) contain valuable metals, epoxy resin, and glass fiber, resulting in them being considered as attractive secondary sources of metals. Due to the complex metal compositions in PCBs, it is difficult to clarify the mechanism of metal separation behavior in the pyrometallurgical recovery process. In this paper, pure Pb, Sn and Cu were used to simulate the effects of temperature, time, particle size and shape on the reaction and separation process. With the increase of temperature and time, the thickness of the interface reaction layer was improved. Under the same temperature and time, the reaction degree of Cu with Sn was greater than that of Cu with Pb. In the separation process, reducing temperature, time and increasing Cu particle size were conducive to the separation and recovery of Pb-Sn alloy by supergravity. Under the same or similar particle size, the recovery of Pb-Sn alloy in irregular Cu particles was lower than that in regular Cu spheres. Improving the gravity coefficient benefited the recoveries of Pb and Sn. The results will provide technical guidance for the separation and recovery of Pb, Sn and Cu from real PCBs.

Copper electroplating technique for development of HTS current leads bottom joints using MgB2 wires

Low resistance, helium leak tight, cryo-stable superconducting (SC) joints with sufficient strength to absorb thermo-mechanical stress are commonly used in large sized magnets, their feeders and current leads (CL). Among high temperature superconductor (HTS), cuprate oxide based tapes are the popular options for CL applications. Recently composite magnesium diboride (MgB2) wires with superconducting transition temperature of 39 K are getting wide attention for low field applications. Use of Monel as a sheath material in MgB2 wires poses a major challenge while fabricating SC joints due to its low wettability and flowability using PbSn alloy based solder material. To tackle this issue, we exploited Cu electroplating technique to ease fabrication of MgB2 – NbTi: Cu as well as HTS: Cu - MgB2 joints. The details of in-house electroplating technique developed to fabricate bottom joints of BSCCO-2223 based HTS CL using MgB2 wires are reported. To study the morphology of such Cu coated MgB2 wires microstructural investigation is performed using Scanning Electron Microscope with energy dispersive X-ray spectroscopy (SEM/EDX) analysis. Similar Cu plated MgB2 wires are used to fabricate bottom joints of a prototype HTS CL. The performance of joints is preliminary attempted in the HTS CL test experiment up to 1.5 kA at 20 K.

Effect of Aging Temperature on the Fatigue Resistance and Shear Strength of SAC305 Solder Joints

The interconnection materials that are used in electronics assembly fabrication operating in harsh environmental conditions are frequently exposed to different types of mechanical stress and fatigue. Fatigue resistance does significantly affect the reliability of electronic assemblies. SAC alloys are commonly utilized in electronic assemblies’ fabrication operating in harsh conditions due to their superior mechanical and fatigue properties. Hence, this provokes the need to model and perform a detailed statistical analysis of their reliability behavior. SAC305 is commonly used as a lead-free alloy which is being utilized as a replacement of the eutectic SnPb alloy. The main goal of this study is to investigate the effect of aging temperature on the fatigue and mechanical behavior of SAC305 solder joints using accelerated shear-fatigue and shear tests. An Instron Microtester machine with a customized fixture was used to perform the tests. A two-factor test matrix for the fatigue test was constructed; where the stress amplitude has three levels (16, 20, and 24MPa) and the aging temperature has four levels (0, 50, 100, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$150^{\circ }\text{C}$ </tex-math></inline-formula> ). Microstructural analysis was performed on samples aged at different temperatures using SEM microscopy to address the evolutions in the precipitates size and the intermetallic compound (IMC) layer. A stress-life equation and an Arrhenius model are used to develop a general reliability model as a function of aging temperature and stress amplitude. The relationship between the fatigue life and the inelastic work were analyzed using Morrow Energy equation. The results indicate a major reduction in the reliability and shear strength of the solder joints with increasing the aging temperature. Aging has been also found to have a more notable effect on the fatigue life when compared to shear strength.

What happens when a Pb–Sn coating deposited on low carbon steel is exposed in an HCl‐polluted wet environment? Development of a corrosion mechanism

AbstractThis article synthesizes all the results obtained to establish a global corrosion mechanism when a Pb–Sn coating deposited on low carbon steel is corroded in an HCl‐polluted wet environment. The successive stages of the process are shown. In HCl‐polluted environment, coupled with water, acid chlorides provide an aggressive electrolyte particularly favorable to corrosion. In contact with this electrolyte, lead products are created as PbCO3 and PbCl2, showing the impact of the surrounding atmosphere. In parallel, the electrolyte concentrates in Sn2+ until saturation, and tin precipitates under different forms. Due to the lead consumption, the lead corrosion products layer breaks, and the coating thins, diffusion pathways are created and the steel oxidizes. Iron corrosion products are similar with or without a coating except for the presence of a tin‐rich filament. Lead is no longer present. The different stages of the mechanism are compared to corrosion phenomena observed during the use of Pb–Sn alloys to provide effective solutions to minimize or even avoid the phenomenon of corrosion.

Simulation of binary alloy columnar solidification in the presence of EM forced convection

The article describes a numerical model of solidification of the SnPb alloy with electromagnetic stirring. The model is based on two open access computational codes. Comparison of the results of the calculation of directional horizontal solidification with natural and electromagnetically forced convection forces is presented. It is shown that the electromagnetic driven flow can affect the final segregation map only at the first stage of the solidification process. Tables 1, Figs 8, Refs 30.

Electrodeposition of lead and lead-tin alloy on copper using an eco-friendly methanesulfonate plating bath

Lead coatings were deposited from an electroplating bath contained mainly a lead salt and free methane sulfonic acid (MSA). Electroplating copper samples with a lead-tin alloy was carried out from a plating bath contained a lead salt, a tin salt and free MSA. An organic additive was added to enhance the surface morphology and therefore the appearance of the coated samples. The parameters affected the coating quality like the plating time, current density, temperature and bath composition are optimized. Surface characterization (FE-SEM & EDX) of the formed coating shows a compact dense layer of Pb or Pb–Sn alloy. XRD of Pb–Sn coating shows clear peaks of each lead and tin. The electrochemical properties of the coated samples was investigated using the electrochemical impedance spectroscopy (EIS). The obtained coatings were compared with those obtained using the fluoroborate bath. It is worthy to mention that the presence of the organic additives markedly improved the quality of the lead coating obtained from the methanesulfonate bath so as to have the same quality of the coating obtained from the fluoroborate bath.

Leaded or unleaded? Homemade microscale tin electroplating

Abstract Social distancing measures due to the SARS-CoV-2 virus have profoundly challenged the educational experimental work. We have sought to remediate this issue by designing a series of low cost, low risk, quick, and qualitative electrochemistry and corrosion experiments to be performed in the student’s homes at the microscale with a kit provided by the teacher. One such experience is the electroplating of Sn from an aqueous chloride solution using readily available soldering wires (e.g., Sn–Pb alloy, or Sn–Ag–Cu alloy). This process catches students’ attention due to its simplicity and variety of possible applications that include corrosion protection, fabrication of electronic components, plating of cooking utensils, lithium batteries, etc.

Numerical modeling and experimental analysis of benchmark experiment of Sn-10 wt%Pb alloy under forced convection by electromagnetic stirring

3D numerical simulation of solidification was carried out for a benchmark experiment on a binary Sn-Pb alloy with rigorous controlled thermal boundary conditions. The experiment consists of solidifying a parallelepiped ingot of Sn-10wt.%Pb composition. The main objective is to give both details of 3D numerical simulation and experimental analysis of the effect of forced convection driven by an alternative traveling magnetic field on the solidification process of Sn-10wt.%Pb alloy. The experiment was carried out under an average experimental temperature difference (DT) equal to 40 K and a cooling rate of (-0.03 K/s). This slow-cooling condition has been used in order to promote segregation formation. A periodically reversed electromagnetic stirring (EM) case with a modulation frequency equal to 0.125 Hz has been investigated in this both numerical and experimental studies. During the solidification process, the time evolution of the temperature field is recorded by more than 68 thermocouples and analyzed. This enables us to determine the temperature evolution over time owing to forced convection. The patterns of the of solute (lead) concentration distribution obtained by numerical results are compared to the experimental X-ray radiographies. A post-mortem analysis is performed allowing us to determine the grain’s form and size in the final macrostructure. Results illustrate clearly that the EM stirring modifies the macrostructure in terms of columnar-equiaxed transition (CET), namely the grain refinement and, on the other hand, it significantly affects the segregation pattern, especially the segregated channel morphology and distribution. Indeed, it shows that this periodicity in the reversal electromagnetic stirring reduces significantly the macrosegregation corresponding to the last liquid solidified, while remaining inactive for reducing the development of segregated channels.

Processing a Sn–Pb Alloy to Produce Tin

Processing a Sn–Pb Alloy to Produce Tin

Structure of interfaces on mechanically renewed Sn, Pb, and Sn-Pb electrodes in acetonitrile solutions of surface inactive electrolytes

• Ideal polarizability regions of Sn and Pb electrodes in AN solutions were found. • Zero charge potentials of Sn and Pb in AN solutions were determined. • Time changes of capacitance curves are observed on Sn-Pb electrode after renewal. • It is shown that Pb atoms are squeezed out to the surface layer of Sn-Pb electrode. • Time effects on renewable Sn-Pb/AN solutions interface were analyzed in detail. The electrical double layer (EDL) structure of mechanically renewed electrodes of Sn, Pb, and Sn-Pb alloy (1 at.% Pb) is studied in acetonictrile (AN) solutions of LiClO 4 by the impedance method and cyclic voltammetry. The potential regions are found in which these electrodes can be considered in good approximation as ideal polarizable. In these solutions, the potentials of zero charge ( E σ = 0 ) on Sn and Pb electrodes are found to be –0.37 ± 0.02 and –0.59 ± 0.02 V (vs. aqueous SCE), respectively. The experimental dependences of the capacitance on the potential are shown to be in good agreement with the classical EDL model of Gouy–Chapman–Stern–Grahame. Based on the results of capacitance measurements carried out on renewed Sn-Pb electrodes, it is found that as the time of exposure of the renewed alloy surface to electrolyte increases, the C vs. E curves indicate that the concentration of lead atoms in the surface layer of alloy also increases, i.e., Pb is the surface-active component of these alloys. By analyzing the observed time effects, the surface coverage of Sn-Pb electrode by lead atoms (θ) is calculated in different time ( t ) after the renewal. It is shown that the θ vs. t dependences well agree with the model proposed earlier that describes the process of surface segregation of atoms of the surface-active component of eutectic alloys by the mechanism of surface diffusion. The kinetics of process of surface segregation of lead atoms on the mechanically renewed Sn-Pb electrode is compared for AN and aqueous solutions. The increase in θ is found to proceed slower in AN solutions than in aqueous solutions of the similar composition. The main reason for the differences observed is proposed.

Sn–Pb alloy processing for commercial tin production

The aim of the research is to develop an optimal method for Sn–Pb alloy processing to obtain a marketable product – high-grade tin O1–O3 (Sn  98.5 %). Laboratory studies were conducted on the refining of the Sn–Pb alloy with the following composition, wt.%: 53–60 Sn; 18–29 Pb, first by vacuum distillation (t = 1085÷1300 °C, P = 15÷100 Рa; τ = 3÷36 h) for As, Sb and Pb sublimation, then by reagent deposition with elemental sulfur and aluminum as part of the Al–Sn master alloy in the presence of NH4Cl for Cu, Fe and Sb separation. This resulted in obtaining a Sn-containing residue (yield ~60 %) of the following composition, wt.%: 92.39 Sn; 0.46 Pb that was subjected to reagent refining to obtain O3 grade tin (metal yield ~68 %) with the following composition, wt.%: 99.5 Sn; 0.009 Pb. It was found that it is feasible to carry out refining from a preliminarily decopperized Sn–Pb alloy to obtain a finished O1 grade product with a direct extraction of 90 %. A schematic diagram was developed and recommendations were formulated for the process regulations on Sn–Pb alloy processing to obtain commercial tin and recover resulting intermediate products and waste. A furnace with separate production of As, Sb, Pb condensates with the following composition, wt.%: 94.2–98.3 As; 5.1–14.5 Sb; 78.9–86.4 Pb, respectively, was chosen as a vacuum distillation unit. The economic effect of processing ~480 ton/year of Sn–Pb alloy (~50.8 % Sn) with the production of ~235 ton/year of O1–O3 grade tin is ~39 million rubles/year.

Exploiting tube high-pressure shearing to prepare a microstructure in Pb-Sn alloys for unprecedented superplasticity

Superplastic Pb-Sn alloys were produced via tube high-pressure shearing (t-HPS), in a single step starting from elemental solid bulks. A Pb-40 wt% Sn alloy showed an exceptional superplastic elongation as high as ∼1870% at a strain rate of 1.0 × 10−3 s−1 at room temperature, thereby elevating the optimum strain rate for maximum elongation under these conditions by more than one order of magnitude over conventional cast Pb-Sn alloys. This unprecedented room temperature superplasticity is attributed to the equiaxed grains having uniform sizes of the order of one micrometer, and in particular to the well-mixed domains of Pb and Sn in nearly equal proportions. This microstructure cannot be attained in cast eutectic or hypoeutectic alloys through conventional thermomechanical processing, but instead it is a direct outcome of t-HPS-generated compositional patterning at room temperature.