Composition Of Intermetallic Compounds Research Articles

Enhanced bonding strength of Al/Fe bimetal by Ni-based alloys Ni-based interlayer prepared by laser cladding technique

In the process of manufacturing aluminum/iron (Al/Fe) bimetal, improving the bonding strength was a crucial consideration. To achieve this goal, this study focused on two aspects: optimizing the composition of intermetallic compounds and modifying the stress state near the interface. The introduction of a Ni-based coating was investigated to accomplish these objectives. The incorporation of the Ni-based coating resulted in a transformation of the phase composition in the reaction layer from the brittle Al-Fe-Si phase to the mechanically superior Al-Fe-Ni phase. Furthermore, significant changes in the morphology of the reaction layer were observed, with the formation of blocky intermetallic compounds adjacent to the Al matrix on the continuous intermetallic phase side. These alterations effectively alleviated stress concentration at the interface, leading to an increase in the shear strength from 50.4 MPa to 117.4 MPa. The findings of this study demonstrated the positive role of the Ni-based coating in mitigating stress concentration at the interface and enhancing the bonding strength of the Al/Fe bimetallic system. By optimizing the phase composition and morphology of the reaction layer, the bonding capability at the interface was significantly improved.

Early wetting and interfacial behavior of Sn-based solder on copper substrates with different roughness

Purpose This paper aims to investigate the effect of solder composition and roughness on early wetting behavior and interfacial reaction under atmospheric conditions. Design/methodology/approach High-speed photography is used to observe the early wetting and spreading process of the solder on the substrate in real time. The morphology of intermetallic compounds (IMCs) was observed by scanning electron microscopy, and the composition of IMCs micro bumps was determined by energy dispersive spectroscopy. Findings With a roughness range of 0.320–0.539 µm, the solder is distributed in an elliptical trilinear pattern along the grinding direction. With a roughness range of 0.029–0.031 µm, the solder spreads in the direction of grinding and perpendicular, forming a perfect circle (except in the case of Sn63Pb37 solder). The effect of three types of solder on early wettability is Sn63Pb37 > Sn96.5Ag3Cu0.5 > Sn. The wetting behavior is consistent with the Rn∼t model. The rapid spreading stage (Stage I) is controlled by the interfacial reaction with n1 values between 2.4 and 4. The slow spreading stage (stage II) is controlled by diffusion with n2 values between 4 and 6.7. The size of Cu6Sn5 formed on a rough substrate is greater than that produced on a smooth substrate. Originality/value Investigating the effect of solder composition and roughness on early wettability. This will provide a powerful guide in the field of soft brazing.

Electrochemical Characteristics of Intermetallic Phases in Al–Cu–Li Alloys

This study provides a comprehensive overview of the electrochemical characteristics of intermetallic compounds (IMCs) commonly encountered in the 3rd generation Al–Cu–Li alloys. The electrochemical measurements were carried out on a AA2070-T8 alloy and surrogate alloys that have the compositions of select IMCs, typically found in AA2070-T8. The effects of environmental variables such as [Cl−] and pH on the corrosion potential, pitting potential, repassivation potential, corrosion rate, and galvanic current of these IMCs were thoroughly evaluated utilizing the electrochemical microcell method. An electrochemical database was documented that covers eight groups of common IMCs in various Al alloys. The findings improve the understanding of interactions between matrix and IMCs in Al alloys, with implications for corrosion mitigation and new materials design.

UFSW tool pin profile effects on properties of aluminium-steel joint

Effects of underwater friction stir welding tool pin profiles were studied on mechanical properties of AA5182 alloy and St-12 steel dissimilar joint. For this purpose, frustum, triangle, cubic, and hexagonal pin profiles were selected. Thermal history, microstructure analysis, tensile strength, and hardness of joint lines were assessed. The obtained results indicated that due to the high cooling rate of water environment conditions, the presence of edges in the tool pin shape (triangle, cubic, and hexagonal) improves internal material flow. Also, edged pin profiles increase the generation of frictional heat, the thickness of Intermetallic Compounds (IMC), and mechanical interlocking at base materials' interface. The hexagonal pin profile had the most significant favourable influence on the aluminium-steel joint properties among selected tool profiles. The chemical composition of IMCs at the materials interface was FeAl3 and Fe2Al5, and the thickest IMC was formed near 6.5 μm. According to the results, the joint's highest tensile strength was ~69% of aluminium alloy strength, which was obtained with a hexagonal pin profile.

Study on diffusion characteristics of Al-Cu systems and mechanical properties of intermetallics

The kinetics of reaction diffusion in Al-Cu binary systems at solid-state temperatures was experimentally investigated. The Al-Cu diffusion couples were heat treated in the temperature rang of 673–813 K for different period of time, respectively. A layer of intermetallic compounds (IMCs) consisting of θ(Al2Cu), η2(Al0.939Cu0.987), ζ2(Al9Cu11.5) and γ1(Al4Cu9) phases was formed in the diffusion region. The thickening of all four IMCs follows a parabolic growth pattern, which can be used to estimate the growth constants of the IMCs. The composition of IMC was quantitatively analyzed by electron probe microanalysis (EPMA), and the interdiffusion coefficients and activation energies were evaluated for each phase. The nanoindentation technique was employed to obtain the hardness, Young's modulus and creep stress index of the IMCs. It was demonstrated that the ζ2(Al9Cu11.5) phase has the greatest hardness of 11.94 GPa, while γ1(Al4Cu9) has the largest Young's modulus of 254.69 GPa and the minimum creep stress index of 10.75.

Electrodeposition of Tantalum Coatings on Nitinol Stent and Composition of Intermetallic Compounds Forming During Electrolysis

The electroreduction of tantalum complexes in a chloride-fluoride melt was studied on tungsten, and nitinol electrodes. It was found that on a nitinol electrode in addition to the peak associated with the discharge of fluoride tantalum complexes, several peaks on the voltammogram related to the formation of intermetallic compounds of nickel and tantalum were observed. The electrodeposition of tantalum coatings from the NaCl-KCl-NaF(10 wt.%)-K2TaF7(10 wt.%) melt onto nitinol stent was investigated. The formation during electrolysis of several intermediate layers between the deposited layer and substrate was found and their microstructure and chemical composition were determined. It was determined that the surface layers of the nitinol are depleted in titanium due to corrosion in the melt. During electrodeposition a barrier intermetallic layer TiNi2.4Ta0.6 is formed, which prevents the penetration of tantalum into the substrate, but does not prevent the diffusion of nickel and titanium from the substrate into the deposited layer of tantalum.

Effect of Er content on the interfacial microstructure, shear properties and creep properties of Sn58Bi joints

The influences of Er content on the interfacial microstructure shear properties and creep properties of Sn58Bi joints were investigated in this study. The intermetallic compound composition of Sn58Bi-xEr/Cu was Cu6Sn5 compound. The addition of Er suppressed the activity of Sn element, decreased the driving force for the growth of Cu6Sn5 intermetallic compound and decreased the thickness of Cu6Sn5 intermetallic compound layer. The shear properties and creep durability of Sn58Bi-xEr/Cu welded joints were improved to a certain extent. At the Er content of 0.1%, the shear strength and creep durability properties of the solder alloy are relatively optimal. When wt%Er was more than 0.1%, with the increasing Er content of rare earth elements, the internal organization of the joint interface is coarsened, and the flatness of the IMC layer at the interface is reduced, which leads to the decrease of the creep performance of the final joint.

Interfacial reactions and mechanical properties of transient liquid-phase bonding joints in Cu/Sn/Ni(P) and Ni/Sn/(OSP)Cu structures for power modules

Power modules are being increasingly used as essential parts in eco-friendly vehicles, and they are generally exposed to high temperatures during operation. To this end, electronic interconnection methods that can enhance durability and help withstand extreme environment are required. In this study, we investigated the properties of transient liquid-phase (TLP) bonding joints, which form various metal structures under different bonding conditions. For TLP bonding, Cu- or Ni-finished Si chips and Ni(P)-finished or organic solderability preservative (OSP)Cu-finished direct bond copper (DBC) substrates were used with Sn preforms. TLP bonding was employed for two types of structures: Cu-finished Si chip/Sn preform/Ni(P)-finished DBC substrate (Cu/Sn/Ni(P) structure) and Ni-finished Si chip/Sn preform/(OSP)Cu-finished DBC substrate (Ni/Sn/(OSP)Cu structure) with a bonding temperature of 300 °C applied for 10, 30, and 60 min under 1 MPa bonding pressure. After TLP bonding under these bonding conditions, interfacial reactions and compositions of intermetallic compounds (IMCs) were analyzed. To evaluate the mechanical properties of these joints, we conducted a low-speed die shear test. The shear strengths of these joints increased with bonding time, regardless of these joint bonding structures. The Ni content in (Cu, Ni)6Sn5 of the Cu/Sn/Ni(P) structure was found to be higher than that in the Ni/Sn/(OSP)Cu structure, which correlated with higher shear strength of joints in the Cu/Sn/Ni(P) structure than those in the Ni/Sn/(OSP)Cu structure.

INTERMETALLIC COMPOUNDS FORMATION OF SOLDER ALLOYS ON Ni/Au SURFACE FINISH COPPER

Intermetallic compounds (IMCs) formation between lead-free solder alloys (Sn-9Zn and Sn-8Zn-3Bi) and Ni/Au surface finish copper substrate were studied. Reaction between the solder and the substrate was carried out at regular soldering temperature, approx. 50 °C above the melting temperature of the solder alloys. Results indicated that Au-Zn was the IMC formed at the interface and the Au layer which is electro-plated on the substrate has completely dissolved into the solder alloys. The amount of Au available at the interface is an important factor that influent the morphology of the IMC with thicker Au layer on the substrate resulted in thicker layer of IMC at the interface. Although Bi does not taken part in the composition of IMC, it influent the formation of IMC, the IMC formed in the Sn9Zn/substrate interface was Au5Zn3, meanwhile it was g2-AuZn3 in the Sn-8Zn-3Bi/substrate interface.

Application of Intermetallics (La,Ce)Ni5 in Hydrogen Energy Storage Systems

The hydrogen sorption characteristics of La1–xCexNi5 alloys (x = 0, 0.1, 0.2, 0.25, 0.5) were studied in the temperature range 298–363 K. The optimal compositions of intermetallic compounds were determined for use as hydrogen sorbents in reusable accumulators: compounds La0.9Ce0.1Ni5 and La0.8Ce0.2Ni5. Based on them, a metal hydride hydrogen accumulator was designed and manufactured and its technical and operational characteristics were found. The developed devices are proposed to be applied in electric energy storage systems using hydrogen as an energy carrier.

Influence of tool offset on microstructure and properties of Mg/Al dissimilar alloys by friction stir welding joints at low heat input

The composition of intermetallic compounds and mechanical properties during friction stir welding of 2024 aluminum and AZ31B magnesium alloys was investigated by using offset tool at low heat input. The macrostructure of the Mg/Al joints was investigated by optical microscope, and microstructure characteristics were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. The fracture section was also observed. It is found that the mechanical strength of the joint slowly decreases as the value of tool offset increases first and then decreases at the Al-side. The result showed that the joints have the best mechanical properties when offset 0.5 mm and the amount of IMCs is low. And it is found that only IMCs Al12Mg17 is found in the joints. Since Al3Mg2 and Al12Mg17 have eutectic temperatures of 450 °C and 437 °C, respectively, the offset caused the temperature to decrease during the FSW process, allowing Al12Mg17, with a lower eutectic temperature, to form easily.

Effects of Temperature–Humidity Treatment on Bending Reliability of Epoxy Sn–58Bi Solder with Electroless Nickel Immersion Gold (ENIG) and Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG) Surface Finishes

An epoxy Sn–58wt.%Bi solder joint was evaluated by a three-point bending test with electroless nickel immersion gold (ENIG) and electroless nickel electroless palladium immersion gold (ENEPIG) surface finishes aged at 85 °C and 85% relative humidity. Scanning electron microscopy and electron probe microanalysis were carried out to study intermetallic compound variation. The morphology, total thickness, and chemical composition of intermetallic compound in epoxy Sn58Bi solder joints were the same as those of Sn–58wt.%Bi solder joints with each surface finish. The average number of bending-to-failure cycles for the epoxy Sn–58wt.%Bi solder/ENIG joints and epoxy Sn–58wt.%Bi solder/ENEPIG was more than 4000 and 5000, respectively. The average number of bending-to-failure cycles of the epoxy Sn–58wt.%Bi solder joint decreased with increasing age. Three-point bending reliability of epoxy Sn–58wt.%Bi solder joints was higher than that of Sn–58wt.%Bi solder with both surface finishes. Cracking of all solder joints subjected to as-reflowed was propagated through the solder matrix. However, after aging for 1000 h, cracking occurred primarily between intermetallic compound layers.

Microstructure characterization and mechanical properties of the continuous-drive axial friction welded aluminum/stainless steel joint

Aluminum alloy and stainless steel were joined by a continuous-drive axial friction welding machine in this study. The effects of welding parameters on the morphology, microstructure, microhardness, tensile strength, and fracture surface of dissimilar joints were analyzed. The distribution, thickness, and composition of intermetallic compound (IMC) were also discussed. Results showed that the formation of flash only was on the aluminum side because 6061 Al underwent extensive deformation during welding. Al and Fe elements diffused at the bonding interface and formed the IMC layer. The IMC thickness near the 1/2 radius was the smallest, and the thinnest at the center region. With the increase of friction pressure, the tensile strength of joint first increased and then decreased. When forge pressure was below 220 MPa, joint strength was approximately linearly related to the forge pressure. Edge regions of joints had achieved metallurgical bonding. The central region was the weak joining, and the fracture surface contained some cracks, IMCs, and a small amount of dimples.

Growth and evolution kinetics of intermetallic compounds in Sn-0.7Cu-10Bi-0.15Co/Cu interface

The morphology and composition of intermetallic compounds (IMCs) formed between substrate and solder play a vital role in the service life and failure of the solder joint, which is the most important part in the research of electronic packaging. Therefore, it is very important to investigate the growth and evolution of IMCs layer in the aging process. In this paper, there are particular phenomena in the interfacial reaction between the Sn-0.7Cu-10Bi-0.15Co solder and Cu substrate. The 0.15 wt% Co added to the matrix solder causes the abnormal transformation in the thickness and morphology of the IMCs. Because the CoSn3 phase is rapidly growing in a porous structure, so the intermetallic compounds are planar in morphology with an increasing thickness. In addition, the thickness of IMCs layer decreases because the CoSn3 with porous structure promotes the dissolution of the IMCs during aging for 200 h at 70 °C. Analytical results indicate that the Co element changes the diffusion channel and mechanism of the IMCs growth at the interface, and affects the growth kinetics of the CoSn3 phase in products; it in turn impacts the morphology and thickness of IMCs and reliability of solder joint.

Some Physical Properties of the New Intermetallic Compound NbCd2

Solid solutions of cadmium in niobium and NbCd2 phase are formed by magnetron sputtering and coprecipitation on substrates moving relative to the flow of Nb and Cd particles. The NbCd2 phase can be described by a tetragonal unit cell with the parameters a = 0.84357 nm, c = 0.54514 nm, and c/a = 0.6426. A very high hole concentration in NbCd2 is established by studying the coating absorption and transmission spectra corresponding to the intermetallic-compound composition near the fundamental absorption edge, determining the band gap, and measuring the carrier mobility. Such a concentration is characteristic of a strongly degenerate semiconductor or metal. The band gap is determined to be 1.26 eV. The variation in the concentration of carriers and their mobility depending on the cadmium concentration in coatings of the Nb–Cd system confirms the occurrence of the NbCd2 phase.

Oxidation of Aluminum Melts with Rare-Earth Metals

Thermogravimetry studies show that the oxidation of aluminum–rare-earth metal (R) melts obeys a parabolic law. The true oxidation rate of the melts is on the order of 10–4–10–3 kg/(m2 s). In the Al–R systems, the minimum oxidation rate corresponds to the compositions of intermetallic compounds. The oxidation rate of a melt is shown to increase with temperature. It is found by IRS (infrared spectroscopy) and XRD (X-ray diffraction) that the melt oxidation products consist of γ-Al2O3, R2O3 (R = La, Ce, Pr, Nd, Y, Sc), CeO2, and rare-earth metal monoaluminates RAlO3 (CeAlO3, LaAlO3, NdAlO3).

Influence of welding parameters on the IMCs and the mechanical properties of Ti/Al butt joints welded by MIG/TIG double-sided arc welding-brazing

Sound welding-brazing butt joints of TiAl6V4 and 5A06 with excellent front and back appearance were obtained by MIG/TIG double-sided arc (DSA) welding-brazing. The relationships between the main welding parameters such as welding speed, TIG welding current and TIG position, the microstructure of the intermetallic compounds (IMCs) and the mechanical properties of Ti/Al butt joints were investigated. Experimental results revealed that the morphology, composition and thickness of Ti-Al IMCs depended on the welding heat input and the heat distribution. With increasing welding heat input and heat concentration, the thickness of the IMCs layers increased, the morphology changed from lamellar to serrated, and the phase composition changed from TiAl3 to TiAl (adjacent to Ti6Al4V) and TiAl3 (adjacent to the weld). Moreover, the relationship between the structure of the Ti-Al IMCs layers and the tensile strength of the joints without reinforcement was discussed further. Some joints achieved a high bonding strength of 240.3 MPa because of serrated IMCs layer with a thickness of 2–6 μm at the brazing joint. The welding-brazing was performed at the welding speed of 15 mm/s, TIG welding current of 80–90 A and TIG position of 0 mm. The lower tensile strength of the other joints was due to either the reduction of the bonding area by the formation of the lamellar IMCs, or the insufficient integrity of the joints caused by the inherent brittleness of the excessively thick IMCs.

Effect of Si on the Formation and Growth of Intermetallic Compounds at Roll-Bonded Aluminum–Steel (Al-St) Interface

The formation and growth of intermetallic compounds (IMC) were investigated using the Al-St clad materials with additional different Si content to aluminum and steel substrate by differential scanning calorimetry, scanning electron microscopy and energy-dispersive x-ray spectroscopy, x-ray diffraction and transmission electron microscopy. The addition of Si to Al (Al-0.8Si/St) can drastically delay the formation of IMC and accelerate the growth of IMC layer. The Si (Al-0.8Si/St) segregates at the interface and inhibits the diffusion of Al atom to steel before the IMC forms, which further decreases the diffusion depth of Al in the steel layer. By contrast, the addition of Si to St (Al/St-0.8Si) has limited impact on delaying the formation and decelerating the growth of IMC layer. The Si (Al/St-0.8Si) hardly affects the diffusion of Fe atom to the aluminum layer. Among the four clad materials, the major IMC layer (η-Fe2Al5) always exhibits the parabolic growth phenomenon. The addition of Si cannot influence the phase compositions of IMC at the interface between the η-Fe2Al5 layer and the aluminum. However, we observe an extra Fe-rich phase β1-Fe3Al at the interface between the Fe2Al5 layer and steel substrate in the Al-0.8Si/St clad material.

Experimental determination of phase diagram in the Zn-Fe binary system

A critical determination of a phase diagram of the Zn-Fe binary system was carried out by EPMA analysis for skillfully prepared and equilibrated two-phase alloys for solid phases and by EDS areal analysis for the Fe solubility in the heterogeneously solidified liquid phase instead of the conventional diffusion couple method. It was newly confirmed that equilibrium compositions of intermetallic compounds tend to shift toward the Fe side compared to the previous phase diagram on the whole and that the solubility ranges of the Γ-Fe3Zn10 and Γ1-Fe11Zn40 phases are much narrower than those in the literature. The critical composition of the second-order order-disorder transition between δ1k-FeZn7 and δ1p-FeZn10 at high temperature was estimated by Vickers hardness measurement. Furthermore, the phase separation, i.e., the first-order transition, between the δ1k and δ1p phases in the low temperature region was directly found out and its equilibrium compositions were confirmed by EPMA analysis for the two-phase microstructures. The width of the δ1k + δ1p two-phase region at 500 °C is only 0.5 at.% and the δ1p decomposes into the δ1k and ζ-FeZn13 phases via a eutectoid reaction at a temperature between 455 °C and 445 °C. While being mostly coincident with those in the previous literature at temperatures between 1000 °C and 600 °C, the solubility of Fe in the liquid (L) Zn phase is about twenty times larger than the assessed value in the literature at temperatures below 500 °C. A eutectic reaction, L → ζ + (ηZn), was confirmed to occur by precise EPMA analysis and DSC measurement.

Effect of iron addition (up to 10,000 ppmw) on silicon purification during Al–Si solvent refining

The effect of iron addition (up to 10,000ppmw) on silicon purification during Al–Si solvent refining is studied in this work. The Al–Si based melts with different iron contents were solidified with different cooling rates. It is found that the iron addition does not affect boron and phosphorus removal rates. Iron distribution in microstructure demonstrates that iron does not have an effect on the diffusion behaviors of boron and phosphorus. The compositions of intermetallic compounds containing iron indicate that there is neither interaction between iron and boron, nor interaction between iron and phosphorus. Besides, the models of interaction between boron and an additive element are proposed.