Dissolution Of Intermetallic Compounds Research Articles

Effect of compositional homogenization on hot workability of Ni-based GH4061 superalloy

Complex solidification process, severe chemical segregation and large amounts of secondary phases with low melting point between dendrites deteriorate the hot workability of as-cast GH4061 superalloy. The effects of the homogenization temperature and time on the dendritic segregation, dissolution behavior of Laves phase with low melting point intermetallic phases and hot workability of the alloy were investigated using OM, SEM, EPMA and TEM. The results show that in the as-cast sample, severe compositional segregation is found among dendritic structures and the highest segregation coefficient of Nb is 2.435, followed by Ti of 1.346 and Mo of 1.200. After homogenization at 1160 °C for 20 h, the segregation among dendritic structures has been fully eliminated and the segregation coefficient of Nb declines to 1.098. Meanwhile, Laves and δ phases are mostly dissolved and no any localized grain boundary re-melting was observed. Increasing annealing temperature accelerates the speed of chemical homogenization and dissolution of intermetallic compounds. High-temperature mechanical properties testing results demonstrate that two-step homogenization treatment promotes the plasticity up to 1150 °C. Fracture analysis reveals that the dissolution of Laves and δ phases reduces the probability of crack initiation and fracture, resulting in a good hot workability.

Effect of SiO2 nanoparticle addition on growth of interfacial Ag3Sn intermetallic compound layers between lead-free solder and silver conductor

This study investigated the effects of silver powder modification on intermetallic compound (IMC) formation and silver leaching during soldering at high temperatures. Silica nanoparticles (NPs) were deposited onto a silver powder surface to inhibit silver leaching, which can lead to soldering joint failure during high-temperature soldering. The NPs were deposited through hydrolysis and a condensation reaction of tetraethyl orthosilicate (TEOS) based on the Stöber method. Fourier transform infrared spectroscopy and scanning electron microscopy were used to observe the microstructures of silver powders after the deposition of silica NPs with various TEOS concentrations and various deposition times. As the deposition time increased, the amount of silica NPs on the surface of the silver powder increased. The transmission electron microscopy results show that silica NPs were located at the IMC grain boundaries, which can hinder the dissolution of IMCs by lead-free solder melt along grain boundaries during soldering, retarding silver leaching. The growth kinetics and mechanism of IMCs during soldering were investigated. The results show that the growth of IMCs is mainly dominated by bulk diffusion. The activation energy for IMC growth increased and the growth rate decreased with increasing silica NP addition and deposition time.

Microstructure evolution in a Fe-Ni-Si alloy during heat treatment and electron irradiation

Experiments have been made on studying structural and phase changes by the residual resistivity method in a Fe-Ni-Si alloy during annealing and electron irradiation. Thermal diffusion starts above 600 K and ensures decomposition of the solid solution up to 700 K; at higher temperatures it provides homogenization of the solid solution with the dissolution of intermetallic compounds in accordance with the equilibrium phase diagram. It is shown that, upon irradiation with electrons above 240 K, vacancy clusters are formed in both the aged and quenched alloys. Dissociation of clusters occurs at temperatures ranging between 350 and 500 K and leads to solid solution decomposition under the influence of diffusion caused by migrating vacancies with the formation of intermetallic precipitates. Irradiation at 423 K causes migration of vacancies and decomposition of the solid solution. In alloys irradiated at both temperatures above 700 K, as well as in unirradiated alloys, the precipitates dissolve in accordance with a single equilibrium dependence.

Improvement of thermomigration resistance in lead-free Sn3.5Ag alloys by Ag interlayer

A significant improvement of thermomigration (TM) resistance in Pb-free Sn3.5Ag alloys was achieved by a Ag interlayer. Ag interlayer was used to form Ag3Sn intermetallic compound (IMC) during reflowing process, which can serve as a barrier to suppress thermomigration-induced Cu flux under a temperature gradient. Two different kinds of sandwich samples were designed and compared, Cu/Ag/Sn3.5Ag/Cu and Cu/Sn3.5Ag/Cu. A heat sink and a heat source were employed to establish a temperature gradient of 7000 °C/cm. The growth rate of IMCs at cold end in Cu/Ag/Sn3.5Ag/Cu was slower than that in Cu/Sn3.5Ag/Cu. Thermomigration-induced Cu fluxes were also effectively inhibited in Cu/Ag/Sn3.5Ag/Cu specimens, and the calculated value of JCu,TM was about one-third times as that in Cu/Sn3.5Ag/Cu specimen. In addition, the dissolution of IMCs and under bump metallization (UBM) at hot end was barely observed in Cu/Ag/Sn3.5Ag/Cu specimen. These results suggest that Ag3Sn layer can be a diffusion barrier to effectively inhibit the Cu flux from hot end to cold end under a temperature gradient. Furthermore, crystallographic orientation of Sn grains was affected by the Ag interlayer, and it leads to the c-axis of Sn grain being more vertical to the direction of JCu,TM for the samples with Ag interlayer deposited, which further enhances the effect of suppression on JCu,TM.

Dissimilar resistance spot welding of 6061-T6 aluminum alloy/St-12 carbon steel using a high entropy alloy interlayer

The microstructure and mechanical properties of dissimilar resistance spot weldments between the sheets of 6061-T6 aluminum alloy and St-12 low carbon steel using Al0·5FeCoCrNi high entropy alloy (HEA) interlayers (with the thicknesses of 0.4, 0.7 and 1 mm) were studied and compared to interlayer-free weldment. Although HEA contained Al and Fe, its microstructure showed no evidence of Al–Fe intermetallic compounds (IMCs). Barely visible interfaces formed at the carbon steel/HEA side of all weldments, suggesting metallurgical consistency between both materials. Conversely, complex IMCs formed at the interfaces of Al/HEA, as a result of strong chemical tendency of HEA constituent elements towards the aluminum alloy. The application of HEA interlayer was found to change the type of the formed IMCs from AlxFey in the interlayer-free weldment to complex IMCs. The latter prevented cracking in the Al-side of the weldments. Meanwhile, it increased the tendency to hot tearing in the Al-side of the weldments. The thickness of HEA interlayer affected the morphology of IMCs. For instance, a 1 mm-thick interlayer produced needle-shaped complex IMCs owing to initial dissolution of IMCs into the molten aluminum and subsequent eutectic solidification. The weldments fabricated by HEA interlayer exhibited improvement of tensile shear load compared to the interlayer-free joint. Distinct fracture mechanisms were involved in the weldments produced with and without HEA interlayer. The pre-existing cracks and hot tearing at the Al-side of the joint were deduced to be responsible for the fracture initiation in the fabricated weldments without and with HEA interlayer, respectively.

An in-situ study on the dissolution of intermetallic compounds in the Al–Zn–Mg–Cu alloy

The in-situ SEM observations and Line-scanning methods were used to observe the atomic concentration distribution and evolution of main elements in intermetallic phase at different solid solution temperatures. The results indicated that the atomic distribution of main elements in η (MgZn2), S (Al2CuMg), Fe-containing (Al7Cu2Fe) intermetallic phases are parabolic through these phases, while the non-main elements uniformly distribute in matrix. The results of Differential Scanning Calorimetry (DSC) and Energy Dispersive Spectra (EDS) indicated that the Zn atoms dissolved into the matrix between 245 and 430 °C, under which the process of η phase transits to S phase occurred. The Cu element of S (Al2CuMg) phase has an obviously diffusion rate at 450 °C, while the Mg element has an obviously diffusion rate when the temperature is higher than 460 °C. Afterwards the atomic concentration dissolution was modelled by diffusion law, and the model results is corresponding to the linear rule, which agrees with the experiment results.

Bubble growth, intermetallic compounds dissolution and their interactions during heating of an Al-5wt.%Mn alloy by in-situ synchrotron radiography

Bubble growth, intermetallic compounds (IMCs) dissolution and their interactions during heating of an Al-5 wt.% Mn alloy were investigated by in-situ synchrotron radiography. During heating, the pores evolve gradually from irregular shape to subglobose, and finally transform to spherical bubbles in the melt. The bubble behavior in the melt can be categorized to three types. Bubbles can accelerate the dissolution of the IMCs into the melt, which can be described by a logistic model.

GTA Weld Brazing a Joint of Aluminum to Stainless Steel

The relationship between heat input, microstructures, and mechanical properties was studied in the gas tungsten arc (GTA) weld brazing process of aluminum alloy and stain-less steel dissimilar metals with a pure aluminum core wire (ER1100). The mechanisms involved were further revealed by hot-dip aluminizing experiments. The intermetallic compounds (IMCs) of the brazing interface consisted of a thin layer of -Fe2Al5 next to the steel, and a thick layer of -Fe4Al13 adjacent to the Al joint, surrounded by eutectic identified to be Al-FeAl6 and Al-Fe2Al9 distributed uniformly in the weld metal. With increasing heat input, the total thickness of the IMCs decreased first, reaching a minimum value of 3.5 m, and then increased. The decrease in IMC thickness with heat input was observed for the first time and had never been reported before in welding or brazing processes. The joint strength increased to a maximum value of 238 MPa and then declined, suggesting an inverse relationship between IMC thickness and joint strength. The results of the hot-dip aluminizing, regarding the relationship between IMC thickness and temperature, were consistent with the change of IMC thickness in the welds. A possible mechanism in action is that interfacial kinetics and thermodynamics play a role in the dissolution and decomposition of the thick layer of -Fe4Al13 into the FeAl6 and Fe2Al9 phase. Promoting the IMC dissolution or decomposition by adjusting welding procedures is a promising new way to control the IMC growth and improve the joint strength.

Experimental and Theoretical Research on the Corrosion Resistance of Ferrous Alloys in Aluminum Melts

The resistance of three ferrous alloys (HT150, QT500, and H13) to corrosion caused by exposure to aluminum melts has been systematically studied using experiments and modeling. Results show that the exfoliation and dissolution of intermetallic compounds like Fe2Al5 and FeAl3 formed by the interdiffusion between aluminum melts and ferrous alloys are responsible for the corrosive attack. Based on the thermodynamics and kinetics of intermetallic compounds, an analytical model has been established to quantitatively account for the corrosion behavior between the ferrous alloys and aluminum melts, and the diffusion inhibition factor λ is first introduced in this work to quantitatively estimate the extent to which the existence of carbon can influence the diffusion of aluminum melts to the ferrous alloys. Theoretical analysis demonstrates that the flake graphite in HT150 can reduce the corrosion rate most effectively, followed by spheroidal graphite in QT500. Both outperform H13.

Microstructural evolution and growth behavior of intermetallic compounds at the liquid Al/solid Fe interface by synchrotron X-ray radiography

The growth of Inter-Metallic Compounds (IMCs) with dissolution was investigated on the liquid Al/solid Fe interconnection by using synchrotron radiation real-time imaging technology. At the initial stage of holding at 850°C, a layer of the η-Fe2Al5 phase formed at the interface, and tongue-like η grew into α-Fe. The tongue-like η phase had a stronger (001) texture than the layered phase. The coalescence of tongue-like η started at the bottom, followed by the dissolution of IMCs, which leads to a further increase in its growth rate. During solidification stage, the dotted, needle-like and flake θ-FeAl3 phases were sequentially formed.

Electromigration Effect on Kinetics of Cu–Sn Intermetallic Compound Growth in Lead-Free Solder Joint

Intermetallic compounds (IMCs) growth is often accompanied by void and crack formation. It can reduce the mechanical properties and reliability of solder joints. In this paper, based on the Cu mass transport mechanisms, a theory model is established to analyze the IMC growth behaviors on Cu/Sn/Cu interconnection structures. The influence of IMC dissolution process is considered to investigate the polarity effect of electromigration (EM) on kinetics of IMC growth. Verified by reported experimental data, the model can accurately calculate the thickness of IMC growth under specific temperature and current stressing. The model reveals that during thermal aging, the thickness growth of IMC on Cu–Sn interfaces has a parabolic curve relationship with time. While under current stressing, EM Cu flux in Sn solder accelerates the anode’s IMC growth and motivates the transition of its thickness growth from parabola-like curves to a linear-like relationship. The cathode’s IMC will reach constant thickness with stressing time, which can be primarily determined by the dynamic equilibrium between Cu dissolution flux and chemical Cu flux. When the initial thickness of IMC is larger than this constant, the IMC on the cathode side follows a parabola-like curve to dissolve. Otherwise, it follows a parabola-like curve to increase.

Letter to the Editor: S. Sreenivasan, S.K. Mishra, K. Dutta. Ratcheting strain and its effect on low cycle fatigue behavior of Al 7075-T6 alloy [Mater. Sci. Eng. A 698 (2017) 46–53

Electromigration will induce polarity effects on the formation and dissolution of intermetallic compounds (IMCs) at the electrodes in conventional solder joints. However, the entire solder joint of a microbump may convert to intermetallic compounds after prolonged current stressing. The present study investigated the growth behavior of intermetallic compounds in a 30 μm height Sn1.8Ag microbump plated on a Cu pillar with or without an intermediate Ni layer when the substrate metallization was either Organic Solderability Preservative-Cu (OSP-Cu) or Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG). The progress of the growth of the intermetallic compounds under a current density of 1.0 × 104 A/cm2 was investigated for up to 300 h. The segregation and growth of the intermetallic compounds revealed by a three-dimensional cross section during current stressing was observed and discussed.

Current induced segregation of intermetallic compounds in three-dimensional integrated circuit microbumps

Electromigration will induce polarity effects on the formation and dissolution of intermetallic compounds (IMCs) at the electrodes in conventional solder joints. However, the entire solder joint of a microbump may convert to intermetallic compounds after prolonged current stressing. The present study investigated the growth behavior of intermetallic compounds in a 30 μm height Sn1.8Ag microbump plated on a Cu pillar with or without an intermediate Ni layer when the substrate metallization was either Organic Solderability Preservative-Cu (OSP-Cu) or Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG). The progress of the growth of the intermetallic compounds under a current density of 1.0 × 104 A/cm2 was investigated for up to 300 h. The segregation and growth of the intermetallic compounds revealed by a three-dimensional cross section during current stressing was observed and discussed.

Electrochemical properties and dissolution of UPd3 in nitric acid solutions

The electrochemical properties of URu3 intermetallic compound (IMC) in 0.5–8 M HNO3 solutions were studied by linear voltammetry and galvanostatic electrolysis. In 0.5–2 M HNO3, URu3 occurs in the passive state at potentials lower than +1.3 V (here and hereinafter, vs. SHE), and in 4–8 M HNO3, an anodic oxidation peak is observed at potentials from +1.0 to +1.2 V. This process, however, leads to IMC passivation and not to its dissolution. At potentials higher than +1.4 V, URu3 passes into the transpassive state and starts to actively dissolve. The principal possibility of electrochemical dissolution of IMC at potentials exceeding the transpassivation potential was demonstrated by galvanostatic electrolysis. The rate of uranium leaching during electrolysis depends to a greater extent on the current density than on the HNO3 concentration and reaches 35 mg cm–2 h–1 in 6 M HNO3 at a current density of 182 mA cm–2.

Interaction Between the Growth and Dissolution of Intermetallic Compounds in the Interfacial Reaction Between Solid Iron and Liquid Aluminum

The interfacial reaction between solid steel and liquid aluminum has been widely investigated in past decades; however, some issues, such as the solid/liquid interfacial structure, formation mechanisms of FeAl3 and Fe2Al5, and interaction between the growth and dissolution of intermetallic compounds, are still not fully understood. In this study, a hot-dipping method is designed to investigate the interfacial reaction in the temperature range between 973 K and 1273 K (700 °C 1000 °C) for 10 to 60 seconds. The intensification of the dissolution leads to the transformation of FeAl3/liquid aluminum into Fe2Al5/liquid aluminum in the solid/liquid structure with increasing reaction temperature. The formation of FeAl3 adhered to the interface depends not only on the reaction mechanism but also on precipitation at relatively low temperatures. In contrast, precipitation is the only formation mechanism for FeAl3 at relatively high temperatures. Austenitizing results in the complete transformation of the tongue-like Fe2Al5/Fe interface to a flat shape. The growth of Fe2Al5 with respect to the maximum thickness is governed by the interfacial reaction process, whereas the growth of Fe2Al5 with respect to the average thickness is governed by the diffusion process in the range of 973 K to 1173 K (700 °C to 900 °C) for 10 to 60 seconds. The dissolution of the parent metal is due to the natural dissolution of FeAl3 at low temperatures and Fe2Al5 at high temperatures.

Intensification of deformation-induced diffusion processes of the dissolution of intermetallic compounds in iron-based alloys at cryogenic temperatures

In an aging austenitic iron-based alloy (Fe–35.8Ni–2.6Ti), when the deformation temperature decreases from 573 to 203–77 K, a sharp intensification of anomalous processes of the dissolution of nanoparticles of the coherent γ'-Ni3Ti phase has been detected upon the interaction with dislocations. This is connected with the suppression (at cryogenic temperatures) of alternative diffusion processes of the precipitation of particles initiated by point defects.

Effects of anisotropic β-Sn alloys on Cu diffusion under a temperature gradient

The diffusion mechanism of Cu in a thin layer of Sn–3.5Ag sandwiched between two Cu foils was systematically investigated under a temperature gradient of 2200°Ccm−1. Experimental observation and theoretical derivation reveal that the microstructural evolutions induced by thermomigration are significantly affected by the tetragonal anisotropy of Sn. The thermomigration flux of Cu increased with the squared value of cos α, the angle between the c-axis of the Sn grain and the temperature gradient. When the c-axis of the Sn grain was parallel to the temperature gradient, a larger thermomigration flux of Cu was induced and the Cu atoms migrated from the hot end toward the cold end. This tended to form a prominent asymmetrical microstructure and cause failure: serious dissolution of intermetallic compounds (IMCs) and excessive consumption of Cu foil occurred at the hot end whereas abnormal accumulation of IMCs was observed at the cold end. Instead, when they are perpendicular, thermomigration would be mitigated due to the lower induced flux. No failure or symmetrical growth of IMCs was found at either interface.

Purification and Recovery of Rhodium Metal by the Formation of Intermetallic Compounds

The catalysts manufacturing industry is the second largest consumer of PGMs after the jewelry industry. Automotive catalysts comprise refractory oxides support on which two or more precious metals (platinum, palladium, rhodium etc.) are dispersed in very low concentration (0.1-0.3 wt.% of the monolith). The honeycomb type monolith is typically made of a cordierite (2Al2O3·2MgO·5SiO2). 2 Several researchers have dealt with the recovery of these metals as the recovery of precious metals from spent automotive catalysts is of economical importance. 3-7 Spent autocatalysts are usually smelted in the presence of larger amounts of collector metals (Cu, Fe, Pb, Ni etc.) After leaching the precious metals enriched in the collector metals with acid, the precious metals can be selectively recovered. Among PGMs, rhodium (Rh) is an exceedingly rare element, comprising only 0.0001 PPM of the earth’s crust. 8 Moreover, rhodium is especially notable for its extreme inertness to acids, even aqua regia. Because of scarcity and high price, the recovery of rhodium from scrap is an important issue. Rhodium has a special catalytic activity to reduce nitrogen oxides (NOx) to N2, and is a main element as an autocatalyst. 9 Rhodium plated electrodes are used in the soda industry for electrolysis of salt water, and for electrodes for domestic water treatment. Rhodium plating is used widely in the jewelry industry. In the electronics industry, rhodium plating is used for electric contacts, e.g., ferreed switches. 10 The purification and recovery of rhodium from the other precious metals has always been difficult because of its complex aqueous chemistry in chloride solution as well as extreme inertness to acids, even aqua regia. It should be pointed out that the key factor for success in the separation of rhodium from the other precious metals is the developing an effective dissolution process for rhodium. It is well known that the disulfate melt technique on rhodium metal is utilized for quantitative dissolution of rhodium and its separation from iridium and platinum. 11 Another method has been developed for recovering PGMs from scrap with the propose of improving Rh dissolution in acid. Reactive metal vapours such as magnesium (Mg) and calcium (Ca) were reacted with powdered Rh in a closed stainless steel reaction vessel at a constant temperature ranging from 873 to 1173 K. 9 Iron(II) oxide with NaCl structure was successfully synthesized in a quartz tube sealed under vacuum. Hematite in an evacuated silica tube progressively loses oxide ions at 1373 K depending on the heating time. Finally, α-Fe2O3 is completely transformed into the well crystallized Fe0.935O after heat treatment at 1373 K for 84 h. 12 Silica tube is very suitable one for the chemical vapour transport reactions in an inert atmosphere because of hightemperature resistance, no-contaminants including foreign metals, and the ease of sealing under vacuum. In this work, the chemical vapour transport reactions between magnesium and rhodium are attempted using silica ampules sealed under vacuum. And also, the verifications, such as the formation and dissolution of intermetallic compounds (MgxRhy), purification and recovery of rhodium, are performed.

Effect of benzimidazoles and potassium oleates on the dissolution of some FeZn alloys in a borate buffer

Anodic dissolution of intermetallic compounds in a borate buffer solution has been studied in comparison with pure metals. Effects of azoles and potassium oleate on the total process and its stages have been determined with allowance for the addition concentrations and time.

The growth and roughness evolution of intermetallic compounds of Sn–Ag–Cu/Cu interface during soldering reaction

The growth behavior and roughness evolution of intermetallic compounds (IMCs) layer between Sn–3.5Ag, Sn–3.5Ag–0.7Cu, Sn–3.5Ag–1.7Cu and Sn–0.5Ag–4Cu lead-free solder alloys and Cu substrate are investigated during soldering under 250 °C. With the increase of Cu content in Sn–3.5Ag, Sn–3.5Ag–0.7Cu and Sn–3.5Ag–1.7Cu solders, the IMC thickness increases due to the decrease of the dissolution rate of the IMCs. The IMC thickness of Sn–0.5Ag–4Cu is quite thinner in a short soldering time. However, with the increase of soldering time, the IMCs layer grows quickly due to the precipitation effect of the Cu 6Sn 5 in the liquid solder. With the increase of soldering time, the roughness of all the IMC layers increases. The roughness of Sn–3.5Ag–0.7Cu and Sn–3.5Ag–1.7Cu interfaces is larger than that of Sn–3.5Ag while Sn–0.5Ag–4Cu/Cu interface has the smallest roughness value. It is believed that the small IMC roughness of Sn–3.5Ag/Cu interface is caused by the IMCs dissolution, and the large IMC/liquid solder interfacial energy maybe the reason for Sn–0.5Ag–4Cu/Cu interface obtaining the smallest IMC roughness.