Cu5Zn8 Phase Research Articles

Electrodeposition of Thin Film Cu-Zn-Sn Alloy for Water Splitting Application

An energy transition to renewable energy sources is necessary due to the scarcity of fossil fuels and their detrimental effects on the environment. Water splitting process is one of the practical and effective way that does not occur spontaneously. This study investigates catalytic activity of Cu-Zn-Sn (CZT) photocatalyst in hydrogen evolution and oxygen evolution reaction. The CZT deposited with varied electrolyte’s pH of 6 and 9 on indium tin oxide substrate at the room temperature for 600 seconds. According to the X-ray diffraction patterns, there were Cu6Sn5, Cu5Zn8, and Sn metal phases with monoclinic, cubic, and cubic crystal systems. The scanning electron microscopy technique results of all CZT alloy sample showed a dense, non-uniform, and polycrystalline surface structure. The CZT alloys were found to have an average particle size of 0.35 μm. CZT alloys can produce a photocurrent density of 0.19 mA/cm² at a potential of 1.29 V vs RHE. the charge transfer resistance of CZT synthesized at pH 6 is lower (21.48 Ω) compared to pH 9 (28.36 Ω). The Tafel slope of HER for pH 9 CZT was -133 mV/dec, which was lower than that of pH 6 CZT (-88 mV/dec), indicating faster H2 production and corrosion resistance on pH 9 CZT.

Microstructure and properties of TiCuZnSn alloy layer on titanium fabricated by friction stir processing

Surface modification is an effective method to improve the surface properties of biomedical titanium. In this study, TiCuZnSn alloy layer was successfully prepared on pure titanium by friction stir processing (FSP). The grain size of the titanium surface-modified layer was significantly refined, accompanied by the formation of Sn3Ti5 and CuZn phases. After annealing heat treatment, the wear and corrosion resistance of the TiCuZnSn alloy layer was significantly improved compared with that of the titanium substrate.

Liquid Metal Embrittlement Cracking in Uncoated Transformation-Induced Plasticity Steel during Consecutive Resistance Spot Welding

In the automotive production line, a single pair of electrodes is employed to produce hundreds of consecutive welds before undergoing dressing or replacement. In consecutive resistance spot welding (RSW) involving Zn-coated steels, the electrodes undergo metallurgical degradation, characterized by Cu-Zn alloying, which impacts the susceptibility to liquid metal embrittlement (LME) cracking. In the present investigation, the possibility of LME crack formation in uncoated TRIP steel joints during consecutive RSW (involving 400 welds in galvannealed and uncoated TRIP steels) was investigated. The results have shown that different Cu-Zn phases were formed on the electrode surface because of its contamination with Zn from the galvannealed coating. Therefore, during the welding of the uncoated TRIP steel, the heat generated at the electrode/sheet interface would result in the melting of the Cu-Zn phases, thereby exposing the uncoated steel surface to molten Zn and Cu, leading to LME cracking. The cracks exhibited a maximum length of approximately 30 µm at Location A (weld center) and 50 µm at Location B (shoulder of the weld). The occurrence and characteristics of the cracks differed depending on the location as the number of welds increased due to the variation in Zn content. Type A cracks did not form when the number of welds was less than 280. Several cracks with a total length of approximately 30 μm were suddenly formed between 280 and 400 welds. On the other hand, type B cracks began to appear after 40 welds. However, the number and size of these exhibited inconsistency as the number of welds increased. Overall, the results have shown that small LME cracks can form even in uncoated steels during consecutive welding of Zn-coated and uncoated steel joints.

Structural and biological analysis of Zn–Cu based biodegradable alloys for orthopedic application

This study focuses on the structural and biological analysis of Zn–Cu based biodegradable alloys for orthopedic applications. Five samples of Zn–Cu based alloys were prepared using a solid-state method at a temperature of 750 °C. X-ray diffraction (XRD) analysis revealed that all samples predominantly exhibited the single phase of Cu5Zn8 with minor peaks of Zn,Fe and Mg.SEM/EDX results shows the coral-like structure with grain size of 160 nm in all samples. The electrical conductivity of the alloys was evaluated through a four-probe analysis, and ZnCu0.5Fe0.4 exhibited the highest electric stimulation (1.5 × 108 S/m) can promote bone growth and aid in the healing process. Optical studies of the Zn–Cu based alloys showed absorption peaks in the range of (335–525) nm, with ZnCu0.5Fe0.4 exhibiting the lowest band gap energy (5.25 eV). The biocompatibility of the alloys was assessed through a simulated body fluid (SBF) immersion test, which indicated that all samples demonstrated biocompatible behavior. ZnCu0.5Mg0.4 exhibited the lowest corrosion rate (0.09 mm/year). Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of the Cu5Zn8 phase and the formation of hydroxyapatite after in vivo testing in all samples. The electrochemical analysis demonstrated the degradation behavior of all samples, with ZnCu0.5Mg0.4 exhibiting the highest corrosion potential (−0.28 V) and improved corrosion resistance compared to the other alloys.

Zn additions modifying microstructure, thermal parameters and cytotoxicity of Sn-0.7Cu eutectic solder alloys

Alloys from the SnCu systems have superior properties as compared to the SnPb alloys, such as mechanical and corrosion resistance. However, SnCu alloys still exhibit low oxidation resistance, poor wettability and low reliability. One way to optimize such properties is by adding alloying elements, such as zinc. Zn is generally used in Pb-free solder alloys to minimize intermetallic compound growth in soldered joints, refine the microstructure and increase mechanical strength, in addition to reducing the final cost. The addition of Zn is motivated by the effects it promotes such as microstructural refining, suppression of intermetallics in the substrate/alloy reaction layer, increase in fluidity and mechanical properties. Therefore, this study aims to understand the effects of Zn additions (0.2 and 0.5 in wt%) on solidification thermal parameters (growth rate-V and cooling rate-Ṫ), macrostructure, microstructure, phase transformation, macrosegregation and cytotoxicity in directionally solidified eutectic Sn-0.7wt.%Cu alloy under transient heat flow regime of solidification in copper sheet. Thus, the samples have been characterized by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD). The CALPHAD (CALculation of PHAse Diagrams) method by Thermo-calc software was used to generate property diagrams and isopleths. Cytotoxicity analysis was performed based on cell viability with incubation periods of 15 and 30 days for the alloys, with subsequent exposures of the extracts for 24 and 48 h. The Zn additions caused slight changes in the phase transformation temperatures of the Sn-Cu-Zn alloys. Macrostructures exhibiting columnar-to-equiaxed transition (CET) were observed for the Sn-Cu-Zn alloys. The microstructures of the Sn-Cu-Zn alloys were predominantly dendritic with a matrix rich in tin (β-Sn) surrounded by a eutectic mixture of the β-Sn + Cu6Sn5 + CuZn phases. After CET on Sn-Cu-Zn castings, low velocity eutectic cells have been observed. Moreover, Zn additions refined and did not change the dendritic arrangement of the Sn-Cu-Zn alloys, when compared to the Sn-0.7wt.%Cu alloy. However, increasing the Zn content did not affect the microstructural scale in the ternary alloys when compared to each other. The variations in the microstructural scale did not influence the toxicity of the examined alloys, but factors such as incubation time and chemical composition did. In general, Zn improved the cell viability of the Sn-Cu-Zn alloys, but still with moderate cytotoxic levels.

Interfacial reactions in the Sn-9.0 wt.% Zn/Cu-Ti alloy (C1990 HP) couple

PurposeThe purpose of this study was to examine the influence of adding a small amount of Ti to a Cu-based alloy, specifically the commercial Hyper Titanium Copper alloy (C1990 HP), which contains Cu-3.28 wt.% Ti, on its interfacial reaction with Sn-9.0 wt.% Zn (SnZn) solder, using the liquid/solid reaction couple technique.Design/methodology/approachThe SnZn/C1990 HP couples were subjected to a reaction temperature of 240–270°C for a duration of 0.5–5 h. The resulting reaction couple was characterized using a scanning electron microscope, energy dispersive spectrometer, electron probe microanalyzer and X-ray diffractometer.FindingsIt was observed that the scallop-shaped CuZn5 and planar Cu5Zn8 phases were formed in almost all SnZn/C1990 HP couples. With increased reaction duration and temperature, the Cu-rich intermetallic compound (IMC)-Cu5Zn8 phase became a dominant IMC formed at the interface. The total thickness of the IMCs was increased with the increase in the reaction duration and temperature. The IMC growth obeyed the parabolic law, and the IMC growth mechanism was diffusion controlled. The activation energy of the SnZn/C1990 HP couple was 64.71 kJ/mol.Originality/valueThis article presents an analysis of the IMC thickness in each sample using ImageJ software, followed by kinetic analysis using Origin software at various reaction temperatures of SnZn/C1990 HP in liquid/solid couples. The study also includes detailed reports on the morphology, interface composition and X-ray diffraction analysis, as well as the activation energy. The findings can serve as a valuable reference for electronic packaging companies that utilize C1990 HP substrates.

Highly lithiophilic and structurally stable Cu–Zn alloy skeleton for high-performance Li-rich ternary anodes

Lithium (Li)-rich ternary alloy, comprising a multi-alloy phase as the built-in three-dimensional (3D) framework and a Li metal phase as a reversible Li reservoir, is a promising high-energy–density anode for rechargeable Li metal batteries. The introduction of metal/metalloid components to the alloy can effectively regulate Li deposition and maintain the dimensional integrity of the Li anode. Herein, the lithium–copper–zinc (Li–Cu–Zn) ternary alloy, as a new type of alloy anode, is synthesized via a facile thermal melting method. The fully delithiated 3D scaffold comprised two Cu–Zn alloy phases named CuZn and CuZn5. These alloy phases exhibit higher lithiophilicity and structural stability than Li–Zn and Li–Cu alloys. Moreover, the CuZn phase is electrochemically inert, ensuring the geometric stability of the anode, while the CuZn5 phase can readily undergo alloying reaction with Li to form the LiZn phase, thereby facilitating uniform Li nucleation and deposition. The hybridized multiphase alloy structure and specific energy storage mechanism of the Cu–Zn based alloy scaffold in the ternary alloy anode facilitate dendrite-free Li deposition and prolonged cycle lifetime. The Li metal full battery based on lithium iron phosphate (LiFePO4) cathode exhibits high cycling stability with high-capacity retention of 95.4% after 1000 cycles at 1C.

Improvement of thermoelectric, hardness, and strength properties with Cu exchange in Zn-based ternary alloy

The electrical properties, hardness, and strength of the Zn-based ternary alloys were determined based on their microstructural properties. Formation and microstructural analyses were performed on Cu5Zn8, Al4Cu9, and Cu3Al intermetallic phases. When the electrical properties of the alloy were examined, it was seen that the electrical resistivity increased according to the amount of Cu. Electrical resistivity values were obtained in the range of 9.7216 ​× ​10−8 −6.5881 ​× ​10−7 Ωm by DC four-point probe method (FPPM). The results obtained with the FPPM showed good electrical resistance, which can be applied to electronics as a lead-free soldering material. For each composition of Zn–Al–Cu alloys, the hardness value was measured within the range of 82.70–94.03 Hv0.1, the ultimate tensile strength (UTS) was measured within the range of 133.48–202.56 ​MPa. In addition, yield strength (YS0.2) was measured within the range of 128.22–174.67 ​MPa. The results of our study are compatible with the expectation that the highest strength, yield strength, hardness etc. properties will be obtained in eutectic alloy systems.

Effects of Bi and Cu addition on mechanical properties of Sn9Zn alloy and interfacial intermetallic growth with Ni substrate

Sn9ZnxBixCu (x = 0, 1.0, 2.0, 3.0 and 4.0 wt%) solder alloys were prepared by adding different contents of Bi and Cu elements, and the effects of Bi and Cu addition on the mechanical properties, wettability, and interfacial intermetallic compound (IMC) layer were researched. The addition of Bi and Cu can significantly improve the mechanical properties and creep resistance of the alloy. When the addition of Bi and Cu reaches 2 wt%, small Bi phases are dispersed in the matrix, and moderate Cu5Zn8 phases appear, which strengthens the solder matrix. The ultimate tensile strength (UTS) of the Sn9Zn2Bi2Cu alloy reaches 51.01 MPa, which is 149.32% higher than that of the Sn9Zn alloy, and the elongation reaches 26.56%. Nanoindentation results show that the holding displacement of the Sn9Zn4Bi4Cu alloy decreased by 28.48% compared with that of the Sn9Zn alloy at a loading rate of 0.1 mN/s. In addition, proper addition of Bi and Cu can improve the wettability of the solder alloy and inhibit the growth of interfacial intermetallic compounds (IMCs) between the solder and Ni substrate. When the reflow time reaches 40 min (min), the interfacial IMC thickness of the Sn9Zn2Bi2Cu/Ni solder joint is 1.93 µm, which is 46.09% smaller than that of the Sn9Zn alloy. Moreover, the shear strength of the Sn9Zn2Bi2Cu/Ni solder joint increases by 33.3%, reaching the maximum value (38.76 MPa). When the Bi and Cu addition reaches 2 wt%, the wetting area reaches a larger value (13.525 mm2), which is 28.35% higher than that of Sn9Zn alloy.

Wear and corrosion behavior of selected up-quenched and step-quenched CuZnSn shape memory alloys

The effect of thermal treatment on the wear and corrosion behavior of three categories of Cu-Zn-Sn-Fe SMAs designated A, B, and C is studied. Wear properties were investigated using a tribometer whilst corrosion in 0.3 M H2SO4and 3.5%NaCl media was studied using the potentiodynamic polarization method. The microstructure of the alloys mainly consists of FCC Cu-rich phase and Cu5Zn8phase. The up-quenched A alloys show the highest hardness and lowest wear rate values of 72.1 HRB and 0.143 mm3/N/m respectively. Average COF was higher for the samples subjected to direct-quenching (0.35–0.12) than the up-quenched (0.16–0.12) and step-quenched (0.2–0.08) samples. Wear occurred by mixed mode mechanisms of abrasion and adhesion evident by grooves and wear particles on the surface. In 0.3 M H2SO4medium, step-quenched alloys had corrosion rates in the range of 0.1022 to 1.1705 mm/yr, which is lower than the range of 0.1466 to 0.2855 mm/yr, and 0.1730 to 0.6027 mm/yr obtained for direct quenched and up-quenched samples respectively. In 3.5% NaCl solution, step-quenched alloys had the lowest corrosion rates 0.0251 mm/yr relative to samples subjected to up-quenching and direct quenching treatment. Generally, step-quenching treatment effectively improved the corrosion resistance of alloys in both media.

Effects of various second phase ratios and contents on microstructure and mechanical properties of eutectic Sn58Bi alloy

A distinctive low melting point heterostructure alloy (LMH) Sn-Bi-Cu-Zn-Ag-Sb was prepared by introducing different ratios and contents of second phase into the eutectic Sn58Bi alloy (SBE). Rapid solidification results in a dispersion of Cu5Zn8, Ag3Sn, and SbSn precipitated phases in Sn53Bi3Cu3Zn2Ag2Sb (LMH32). Besides, the nano-sized η'-Cu6Sn5 and Ag3Sn phases were also observed in the alloy matrix. During solidification, the Cu5Zn8 and Ag3Sn phases are used as the heterogeneous nucleation matrix of the Sn and Bi phases, which significantly refines the eutectic structure and leads to fine-grained strengthening. And the formation of Sn(Sb) solid solution phase leads to solid solution strengthening. The significant mechanical incompatibility between the matrix and the second phases of the LMHs produces a higher back stress hardening effect. The coupling effect of multiple strengthening mechanisms causes the ultimate tensile strength (UTS) of LMH32 reaches 102 MPa, higher 88.9% than that of SBE, and the elongation reaches 12.8%, but the melting point does not change significantly.

Phase Formation and Diffusivity in the Ternary Cu-Zn-In System

Formation of the phases in Cu-Zn-In system was investigated by means of diffusion multiples annealed in isothermal conditions. The annealing of three different configurations of joints was performed at increasing temperatures (130, 350, 450 °C): below and above melting temperature of In and above Zn melting temperature. It was found that In revealed the ability for the preferential diffusion in Zn along the grain boundaries, forming the eutectic phase. In all applied temperatures, pure Cu was the barrier for the diffusion of In, while the diffusion of Zn proceeded easily, leading to the formation of binary CuZn phases; the phases from the Cu-In system were not found. The ternary Cu-Zn-In phases were formed at temperatures of 350 and 450 °C, at which the simultaneous diffusion of In and Zn in Cu took place, with participation of liquid In and Zn. The obtained results are the starting point for the calculation of the Cu-Zn-In phase diagram which remains unavailable, in spite of fact that all Cu-Zn, In-Zn and Cu-In binary diagrams are well known.

Brass Alloy Coatings Electrodeposited from an Environmentally Friendly Alkaline Lactate Bath under Different Operating Conditions

The electroplating of brass alloy coatings onto a steel substrate was established using a lactic acid solution under diverse practical conditions. CuSO4.5H2O, ZnSO4.7H2O, CH3CHOHCOOH, and anhydrous Na2SO4 were used to make the deposition bath. The impact of bath components, deposition current, as well as temperature on the current efficiency (CE) and alloy microstructure was examined. The deposition of the alloy is of the normal type. The CE is good, and it improves when the [Zn2+] / [Cu2+] ratio in the bath increases. On the other hand, the efficacy declines when the current density, temperature, and lactic acid concentration increase. By elevating the applied current density, or raising the concentration of the Zn2+ ions in the tub, the amount of Zn metal in the plated alloy is increased. SEM, energy dispersion X-ray, and X-ray diffraction techniques are being used to investigate the coating’s morphology and crystal texture. The presence of copper and zinc metals in the deposit was confirmed by EDX analysis. The new bath’s deposits are well-crystalline and contain a Cu5 Zn8 phase. The bath’s throwing power and throwing index are determined, and it is found that the alkaline lactate tub has satisfactory throwing power and throwing index.

Effect of heat treatment on microstructure evolution, phase transformation and mechanical properties of dual phase Cu-Zn alloy

Effects of heat treatment conditions on the microstructure evolution, phase transformation and mechanical properties of dual phase Cu-Zn alloy were systematically investigated. Meanwhile, the relationship between the nano-hardness and the macroscopic hardness was also discussed in the study. The results show that the β phase rich in Zn, has the phase transformation temperature from 456.5 °C to 827.1 °C. With the increasing of heat treatment temperature, significant (200) (220) α phase to (200) (211) β phase transformation occur and the β phase fraction increases from as-received 13.1–41.3%. The grain becomes coarser and grows rapidly from 32.6 µm to 49.7 µm from temperature 550 °C to 800 °C, the increase of β phase results in the strength increases and the fracture elongation decreases. The β phase fraction has not varied significantly at temperature 750 °C and 800 °C, the strength has a further increase which is mainly attributed to a part of fine needles of Widmanstätten phase begin to form. At the same displacement, the β phase exhibits a much larger load than that of the α phase, the material pile-ups around indent edges of the α phase becomes more evident indicating that the α phase is softer and has a better ductile. The big difference in the predicted hardness and the macroscopic hardness when heat treatment at 750 °C and 800 °C is mainly attributed to the formation of the fine needles of Widmanstätten phase.

Impact of precipitated phases on the microstructure and mechanical properties of eutectic Sn58Bi alloy

A new type of low-melting-point heterogeneous alloy (LMH), based on Sn58Bi alloy (SBE), was prepared using Cu, Zn, Ag, and Sb microalloying and rapid solidification. The addition of Cu and Zn elements in equal mass ratios resulted in the Cu5Zn8 phase being dispersed in the Sn55Bi3Cu3Zn (LMH3) alloy. Subsequently, the additional Cu reacted with Sn to form a nano-sized η′-Cu6Sn5 phase at the interface of the Sn-Bi eutectic phase. Sn53Bi3Cu3Zn2Ag2Sb (LMH32) was prepared by adding appropriate amounts of Ag and Sb based on LMH3, leading to the precipitation of Ag3Sn and SbSn phases in the SBE matrix. The different precipitated phases in turn produced different types of fiber textures that existed in the matrix phase of SBE, LMH3, and LMH32. In addition, compared to LMH3, the presence of Ag3Sn and SbSn phases in LMH32 caused the formation of Bi twins identified via electron backscattered diffraction. The twin planes (101̅1) and (11̅02) had corresponding rotation axes and rotation angles of 93.8°[7̅431] and 90.2°[5̅415̅], respectively. Nanoindentation results indicated that LMH32 exhibited higher creep resistance than Sn55Bi3Cu3Zn (LMH3) and SBE. The precipitated phase significantly refines the grain size and eutectic lath structure of the matrix phase (Sn and Bi). During the deformation process, the fine lath structure and the interfacial η′-Cu6Sn5 nanophase can hinder the slippage of the eutectic interface. Moreover, the presence of the precipitated phase forms a large strain gradient in the alloy matrix, which produces a significant back-stress hardening effect and induces substantial dislocation nucleation. The formation of more dislocations made the creep mechanism of LMHs depend on dislocation climbing.

Research on the Performance of Brass Alloy Main transformer terminal

In order to determine the material of the main transformer terminal, the electrical conductivity, mechanical properties and stress corrosion resistance of brass alloy terminal were studied by XRD, mechanical properties test and ammonia fumigation test. The results show that H59 alloy consists of (Cu, Zn) phase, Cu5Zn8 phase and CuZn phase, H70 alloy consists of (Cu, Zn) phase and dendritic Cu0.64Zn0.36 phase, H80 alloy and H90 alloy are both (Cu, Zn) phase. With the increase of Cu content, the strength of brass decreases, the conductivity increases, and the stress corrosion resistance increases. H90 alloy has excellent plasticity and toughness, excellent resistance to ammonia fumigation stress corrosion, and can be used as main transformer terminal material.

Modification of Corrosion and Mechanical Behaviour of Cu-Zn-Al Shape Memory Alloy

shape memory alloys (SMAs) exhibit an interesting research topic. The currentss limitationss to thes SMAsss is thats the cost of SMAss, mades outs ofs expensive elements such as Ni and Ti. In this work, the influence of different amount of nickel (Ni), boron (B), and boron oxide (B6O) additionss ons the structure, mechanicalss, electrochemical, and tribological behaviourss of Cu - Zn - Alss SMAsss have been investigateds.Cu–25Zn–4Al SMAs were produced by powder metallurgy technique with and without the addition of 0.5, 0.7, and 1 wt.% of Ni or B. After mixing the powders for 4hr, the alloys were prepared using 675MPa compact pressure. The alloys were subjected to sintering process in vacuum tube furnace with three stepsss. For microstructural and phases characterisation of alloyss withs and withouts the additions of elements (Ni, B), optical microscopy (OM), scanningss electronss microscopyss (SEM), and XRD diffractions analysiss weres carrieds outs. The transformation temperatures of alloys with and without the addition of elements (Ni, B) were measured by differentials scannings calorimetrys (DSC). The shape memory properties of alloyss withs and withouts the additions of elements (Ni, B) were investigated using shape memory effect test (SME). Electrochemical corrosion tests for alloys with and without the addition of elements (Ni, B) were carried out using potentiodynamic polarization technique. XRD and microstructural analysis showed that all alloys compositions consisted of the predominating Cu5Zn8 phase. The results of transformation temperatures showed that the Ni and B additions have strong influences ons the transformations temperaturess of Cu – Zn – Al SMAs.The results of electrochemical corrosion tests showed that an increased in Ni or B content up to 1wt. % improved the corrosions resistances of the unmodified Cu – Zn – Als SMA in 3.5 NaCls. In the second part, the influence of different amount (1,3, and 5 wt. %) of boron oxide (B6O) additionss ons the mechanicalss and tribology properties of Cu – Zn – Als SMAsss with the addition of 1wt.% Ni or 1wt.% B has been investigated. s Hardness measurements was usedss to assessss the mechanicalss propertiesss of 1, 3, and 5 wt.% B6O modified Cu – Zn – Al – Ni or Cu – Zn – Al – B alloy compositions. Wet sliding wear process was investigated for 1, 3, and 5 wt.% B6O modified Cu – Zn – Al – Nis or Cu – Zn – Als – B alloy compositions in distilled water at 2, 5, and 10 N normal load at room temperature. The resultss of hardness measurements show that an increase in B6O content up to 3 wt.% improved the hardness of Cu – Zn – Als – Ni and Cu – Zn – Als – B SMAss. The tribological results show that the wear resistance of Cu – Zn – Als – Ni and Cu – Zn – Al – B SMAs exhibiteds the best results with 3 wt. % of B6O addition. Further increase or decreases of B6O contents decreases the wears resistances of the alloys.

The Effect of Thermal Annealing on the Microstructure and Mechanical Properties of Sn-0.7Cu-xZn Solder Joint

The microstructural properties of a Pb-free solder joint significantly affect its mechanical behaviours. This paper details a systematic study of the effect of the annealing process on the microstructure and shear strength of a Zn-added Sn-0.7Cu solder joint. The results indicated that the IMC layer’s thickness at the solder/Cu interface increases with annealing time. The interfacial IMC layer of the Sn-0.7Cu solder joint gradually thickened with increasing annealing time and annealing temperature, while the interfacial IMC layer’s morphology changed from scallop-type to layer-type after the annealing process. However, the addition of 1.0 wt.% and 1.5 wt.% Zn in the Sn-0.7Cu effectively altered the interfacial IMC phase to Cu-Zn and suppressed the growth of Cu3Sn during the annealing process. The single-lap shear tests results confirmed that the addition of Zn decreased the shear strength of Sn-0.7Cu. The interfacial IMC of the Cu6Sn5 phase in Sn-0.7Cu changed to Cu-Zn due to the addition of Zn. The shear fractures in the annealed solder joint were ductile within the bulk solder instead of the interfacial IMC layer. Increased annealing time resulted in the increased presence of the Cu-Zn phase, which decreased the hardness and shear strength of the Sn-0.7Cu solder joint.

Effects of four carboxyl-containing additives on imitation gold electroplating Cu-Zn-Sn alloys in an HEDP system

The requirements for using noncyanide imitation gold plating as decorative electroplating are increasing; thus, continuously improving the quality of the coating of the imitation gold plating and optimizing the coating process have become the current priority. In this experiment, hydroxyethylidene diphosphonic acid (HEDP) was used as the main complexing agent; CuSO4·5H2O, ZnSO4·7H2O, and NaSnO3·3H2O were the main salts; and NaOH and sodium carbonate were used as the buffers to prepare the electroplating solution. Using sodium citrate (SC), sodium potassium tartrate (SS), sodium gluconate (SG), and glycerol (Gl) as four additives, the effects of the number of carboxyl groups on the properties of a Cu-Zn-Sn alloy coating were compared. The electrochemical analysis showed that Cu-Zn-Sn alloy codeposition occurred at -0.50 Vvs.Hg|HgO. The scanning electron microscopy (SEM) results showed that the grain size of the coatings obtained with carboxyl-containing additives was more uniform than that obtained with the electroplating solution without additives. The X-ray fluorescence spectrometry (XRF) analysis revealed that the composition of the Cu-Zn-Sn alloy coating obtained by using SC as an additive in the electroplating solution was 89.75 wt% Cu, 9.61 wt% Zn, and 0.64 wt% Sn, and the color of the coating was golden yellow. The X-ray diffraction (XRD) pattern showed that the coating was a mixture of Cu, Cu5Zn8, CuSn, Cu6Sn5, and CuZn phases. The analysis of the electroplating solution by UV, IR, and NMR spectroscopy methods indicates that the additives improve the coating by affecting the complexation reaction of metal ions. These results can provide technical guidance for developing Cu-Zn-Sn ternary alloy electrodeposition technology with the new cyanide-free HEDP alkaline electroplating system.

Effects on Microstructure and Corrosion Behavior of a Heat Treated CuZn36Pb2 Brass

The brass CuZn36Pb2 is widely used for fittings, valves and other installation materials. Failures are observed occasionally caused by corrosion. Considering the Cu-Zn phase diagram only α-phase exists in the range of 650 and 300 °C. At higher temperatures α- and β-phase is stable and at lower temperatures α- and β´-phase exist. Since the β-phase is Zn-enriches, it is attacked severely by corrosion. In the recent work brass samples were heat treated at temperatures between 850 and 200 °C to study the microstructural changes and the corresponding electrochemical properties. Potentiostatic corrosion tests were applied in artificial fresh water and sea water at different potential settings. After a heat treated at 850 °C the brass has formed b-phase which can be shown by metallography. At lower temperatures the microstructure is fine grained and no β-phase was observed. To verify the presence of β´-phase a heat treatment at 200 °C was performed but no β´-phase was observed, which was confirmed additionally by X-ray diffraction. Again, after corrosion tests the samples were investigated by metallography and the β-phase was obviously more attacked than the α-phase.