Effect of the addition of In on the microstructural formation of Sn–Ag–Zn lead-free solder

The effect of addition of In, up to 1 wt.%, on the formation of intermetallic compounds (IMCs) in the solidified Sn–3.7%Ag–0.9%Zn lead-free solder was investigated. As observed by microstructural analysis, the typical structure of Sn–Ag–Zn solder is composed of β-Sn phase and mixed granules of Ag₃Sn and AgZn IMCs. After alloying with In, it evolves into a mixture of randomly distributed rods and granules of Ag₃Sn and AgZn. Clearly, the addition of In into the explored Sn–Ag–Zn solder promotes the formation of rod-like IMCs for the reason that the growth competition of the Ag₃Sn and AgZn IMCs was destroyed by the selective adsorption of In atoms on a certain preferable crystalline planes of the separated IMCs. The change in the morphology of the formed IMCs leads to a great difference in the mechanical performances, for example, the measured microhardness of the investigated solders evolves from 16.95 HV to 21.35 HV with the increase of In content.     

Microstructural evolution of intermetallic compounds in Sn–3.5Ag–X (X = 0, 0.75Ni, 1.0Zn and 1.5In)/Cu solder joints during liquid aging

In this paper, the microstructural evolution of IMCs in Sn–3.5Ag–X (X = 0, 0.75Ni, 1.0Zn, 1.5In)/Cu solder joints and their growth mechanisms during liquid aging were investigated by microstructural observations and phase analysis. The results show that two-phase (Ni₃Sn₄ and Cu₆Sn) IMC layers formed in Sn–3.5Ag–0.75Ni/Cu solder joints during their initial liquid aging stage (in the first 8 min). While after a long period of liquid aging, due to the phase transformation of the IMC layer (from Ni₃Sn₄ and Cu₆Sn phases to a (Cu, Ni)₆Sn₅ phase), the rate of growth of the IMC layer in Sn–3.5Ag–0.75Ni/Cu solder joints decreased. The two Cu₆Sn₅ and Cu₅Zn₈ phases formed in Sn–3.5Ag–1.0Zn/Cu solder joints during the initial liquid aging stage and the rate of growth of the IMC layers is close to that of the IMC layer in Sn–3.5Ag/Cu solder joints. However, the phase transformation of the two phases into a Cu–Zn–Sn phase speeded up the growth of the IMC layer. The addition of In to Sn–3.5Ag solder alloy resulted in Cu₆(Sn_x,In_1?x)₅ phase which speeded up the growth of the IMC layer in Sn–3.5Ag–1.5In/Cu solder joint.     

Study on the properties of Sn–9Zn–xCr lead-free solder

The influences of different Cr content to lead (Sn)–Zn solder were investigated. Sn–9Zn–xCr shows finer and more uniform microstructure than Sn–9Zn. Thermal gravimetric analysis (TGA) and Auger electron spectroscopy (AES) results show that adding Cr significantly improves the oxidation resistance of Sn–9Zn solder, and reduces the thickness of oxidation film of Sn–9Zn–xCr solder. When Cr content is 0.1%, the Sn–9Zn–0.1Cr solder have the best oxidation resistance. In addition, the effect of Cr addition on the wettability, melting point and mechanical properties of Sn–9Zn solder was discussed.     

Thermal stability and primary phase of Al–Ni(Cu)–La amorphous alloys

Thermal stability and primary phase of Al_85+xNi_9−xLa₆ (x = 0–6) and Al₈₅Ni_9−xCu_xLa₆ (x = 0–9) amorphous alloys were investigated by X-ray diffraction and differential scanning calorimeter. It is revealed that replacing Ni in the Al₈₅Ni₉La₆ alloy by Cu decreases the thermal stability and makes the primary phase change from intermetallic compounds to single fcc-Al as the Cu content reaches and exceeds 4 at.%. When the Ni and La contents are fixed, replacing Al by Cu increases the thermal stability but also promotes the precipitation of single fcc-Al as the primary phase.     

The phase equilibria of the Al–Ce–Ni system at 500 °C

The phase equilibria at 500 °C in the Al–Ce–Ni system in the composition region of 0–33.3 at.% Ce are investigated using XRD and SEM/EDX techniques applied to equilibrated alloys. The previously reported ternary phases and the variation of the lattice parameters versus the composition for different solid solution phases are investigated. It is confirmed that τ₂(Al₂CeNi) exists at 500 °C, while τ₃(Al₅Ce₂Ni₅) does not exist at 500 °C. A new compound τ₉ with composition of about Al₃₅Ce_16.5Ni_48.5 is found. The solubility of Ni in Al₁₁Ce₃ and αAl₃Ce is generally about 1 at.%, while the solubility of Ni in Al₂Ce is measured to be 2.7 at.%. The solubility of Ce in Al₃Ni, Al₃Ni₂, AlNi and AlNi₃ is all less than 1 at.%. The solubility of Al in CeNi₅, Ce₂Ni₇ and CeNi₃ is measured to be 30.4, 4.8 and 9.2 at.%, respectively, while there is no detectable solubility for Al in CeNi₂. A revised isothermal section at 500 °C in the Al–Ce–Ni system has been presented.     

Crystallographic Features of Phases Involved in the Oxidation of Ti<Subscript>3</Subscript>Ni<Subscript>3</Subscript>CrSi<Subscript>6</Subscript>

The oxidation behaviour of Ti₃(Ni,Cr)₃CrSi₆ and Ti₄Ni₄Si₇ was studied in air both at 1000 and 1100 °C. The formation of the oxidation products and the phase transformation were characterized by in situ X-ray diffraction and SEM-FEG post-mortem observations. The crystal structure of Ti₃(Ni,Cr)₃CrSi₆ was also determined using powder X-ray diffraction and Rietveld refinement in order to describe this phase as a pseudolamellar structure comparable to the one of Ti₄Ni₄Si₇. Results evidenced that diffusion in solid state governs the oxidation rate of these silicides. Ti₄Ni₄Si₇ oxidation rate was assessed as being one order of magnitude lower than the one of Ti₃(Ni,Cr)₃CrSi₆, while this latter readily transformed into Ti₄Ni₄Si₇ during the first time of oxidation. The understanding of this particular behaviour in which the oxidation rate of Ti₃(Ni,Cr)₃CrSi₆ was not affected by the phase transformation implied to consider the crystallographic lamellar features of these compounds that play a major role in the diffusion of the most oxidizable elements.     

Influence of thermal cycling on shear strength of Cu–Sn3.5AgIn–Cu joints with various content of indium

This work presents an investigation on the influence of thermal cycling of Cu–Sn3.5AgIn–Cu joints for various content of indium. Solders Sn–3.5Ag containing 0, 6.5 and 9 mass% In were prepared by rapid quenching of appropriate alloys. Joints Cu–solder–Cu were prepared in furnace at 280 °C and 1800 s. Thermal cycling was in the interval room temperature (RT)–150 °C up to 1000 cycles and in the interval RT–180 °C for 500 cycles. The shear strength of the joints with indium-free solder decreases with increasing number of cycles. On the contrary shear strength of joints with indium containing solders increases with increasing number of cycles. It is related with the thickness of Cu₆Sn₅ phase which makes the interface between Cu substrate and solder. In the first case the thickness of this phase is growing with increasing number of cycles, in the second case the amount of this phase is reducing with increasing the number of cycles due to the support of dissolution of copper from Cu₆Sn₅ phase into the Sn–Ag–In solder by indium. X-ray diffraction analysis of original solders as well as of uncycled and 1000 times cycled joints made with all three kinds of solders is given.     

The isothermal section of the Gd–Ni–V ternary system at 773 K

The phase equilibria of the Gd–Ni–V system at 773 K were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The experimental results show no existence of ternary compounds at 773 K. The existence of 14 single-phase regions, 25 two-phase regions and 12 three-phase regions was determined. The maximum solubility of V in (Ni), Gd₂Ni₁₇, GdNi₅ and GdNi₂ was measured to be about 16 at.%, 2 at.%, 3 at.% and 2.5 at.%, respectively, while that of Gd in (Ni), Ni₃V, Ni₂V, Ni₂V₃, NiV₃ and (V) was less than 1 at.%. An isothermal section of the Gd–Ni–V system at 773 K has been presented according to the present work.     

DO22–(Cu,Ni)3Sn intermetallic compound nanolayer formed in Cu/Sn-nanolayer/Ni structures

The present work conducts crystal characterization by High Resolution Transmission Electron Microscopy (HRTEM) on Cu/Sn-nanolayer/Ni sandwich structures associated with the use of Energy Dispersive X-ray (EDX) analysis. The results show that DO₂₂–(Cu,Ni)₃Sn intermetallic compound (IMC) ordered structure is formed in the sandwich structures at the as-electrodeposited state. The formed DO₂₂-(Cu,Ni)₃Sn IMC is a homogeneous layer with a thickness about 10 nm. The DO₂₂–(Cu,Ni)₃Sn IMC nanolayer is stable during annealing at 250 °C for 810 min. The formation and stabilization of the metastable DO₂₂–(Cu,Ni)₃Sn IMC nanolayer are attributed to the less strain energy induced by lattice mismatch between the DO₂₂ IMC and fcc Cu crystals in comparison with that between the equilibrium DO₃ IMC and fcc Cu crystals.     

Experimental study of Ti–Sn–Y system phase equilibria at 473 K

The phase equilibria of the Ti–Sn–Y ternary system at 473 K have been investigated mainly by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). The existences of 10 binary compounds, Ti₃Sn, Ti₂Sn, Ti₅Sn₃, Ti₆Sn₅, Ti₂Sn₃, Sn₃Y, Sn₂Y, Sn₁₀Y₁₁, Sn₄Y₅ and Sn₃Y₅ were confirmed. The 473 K isothermal section was found to consist of 13 single-phase regions, 23 two-phase regions and 11 three-phase regions. There is no new ternary compound found in the work. None of the phases in this system reveals a remarkable homogeneity range at 473 K.     

Comment on “Tritium absorption–desorption characteristics of LaNi4.25Al0.75”

The thermodynamic data for LaNi_4.25Al_0.75 tritide, reported by Wang et al. (W.-d. Wang et al., J. Alloys Compd. (2006), doi:10.1016/j.jallcom.206.09.122), are in variance with our published data. The plateau pressures for the P–C–T isotherms at all temperatures are significantly lower than published data. As a result, the derived thermodynamic parameters, ΔH° and ΔS°, are questionable. Using the thermodynamic parameters derived from the data reported by Wang et al. will result in under estimating the expected pressures, and therefore not to provide the desired performance for storing and processing tritium.     

Phase equilibria of the Sn–Ag–Ni ternary system and interfacial reactions at the Sn–Ag/Ni joints

There are no previous phase equilibria studies of the Sn–Ag–Ni ternary system, even though the phase equilibria information is important for the electronic industry. The isothermal section of the Sn–Ag–Ni ternary system at 240 °C has been determined in this study both by experimental examination and thermodynamic calculation. Experimental results show no existence of ternary compounds in the Sn–Ag–Ni system, and all the constituent binary compounds have very limited solubilities of the ternary elements. The binary Ni₃Sn₂ phase is very stable and is in equilibrium with most of the phases, Ag₃Sn, ζ-Ag₄Sn, Ag, Ni₃Sn₄ and Ni₃Sn phases. A preliminary thermodynamic model of the ternary system is developed based on the models of the three binary constituent systems without introducing any ternary interaction parameters. This ternary thermodynamic model is used with a commercial software Pandat to calculate the Sn–Ag–Ni 240 °C isothermal section. The phase relationships determined by calculation are consistent with those determined experimentally. Besides phase equilibria determination, the interfacial reactions between the Sn–Ag alloys with Ni substrate are investigated at 240, 300 and 400 °C, respectively. It is found that the phase formations in the Sn–3.5wt%Ag/Ni couples are very similar to those in the Sn/Ni couples.     

Thermodynamic properties of the ternary system InSb–NiSb–Sb in the temperature range 640–860 K

The ternary InSb–NiSb–Sb system has been studied by X-ray diffraction and by potentiometry. The electromotive forces (EMF) have been measured in the temperature range 640<T/K<860 by using the following galvanic cell:

with x (0.075<x<0.498) and y (0<y<0.359). The investigated samples are located on the following lines of the Gibbs triangle: InSb–Ni_0.33Sb_0.66, InSb–Ni_0.48Sb_0.52, InSb–NiSb, Sb–(InSb)_0.75(NiSb)_0.25, Sb–(InSb)_{0. 5}(NiSb)_0.5, Sb–(InSb)_0.25(NiSb)_0.75. From these measurements, the values of the partial molar thermodynamic functions (Δμ°_m,In, ΔH°_m,In, ΔS°_m,In) (data at reference pressure p⁰=10⁵ Pa), for the liquid InSb alloy, for the three solid heterogeneous regions InSb–NiSb₂–Sb, InSb–NiSb_1±δ?–NiSb₂, InSb–NiSb_1±δ, for six ternary liquid–solid alloys, have been calculated.     

Electrodeposition of ternary Zn–Ni–Sn alloys from an ionic liquid based on choline chloride and their characterisation

Ternary Zn–Ni–Sn alloy coatings with a range of compositions were potentiostatically electrodeposited on steel substrates from a deep eutectic solvent-based electrolyte. The effect of electrodeposition potential on the morphology, chemical and phase compositions, and corrosion behaviour of the deposits was analysed. The co-deposition mechanism of Zn–Ni–Sn alloys was found to be normal whereby increasing the electrodeposition potential enhanced the ternary alloy Zn content (active element) and greatly suppressed the alloy Sn and Ni content (noble elements). The X-ray diffraction phase analyses showed that Ni in the deposits exists in the form of metal compounds including β-Ni₃Sn₂ as well as γ-NiZn₃. The improved corrosion resistance observed in all ternary alloys was attributed to their compact morphology, phase content and chemical composition. Comparison of corrosion performances shows that ternary Zn–Ni–Sn alloys are superior for sacrificial corrosion protection of steel metallic substrates compared to binary Zn–Sn and Zn–Ni alloys.     

The isothermal section of the Ni–Sn–Zn phase diagram at 873 K

The phase equilibria of the Ni–Sn–Zn ternary system were experimentally investigated at 873 K in the framework of the COST Action MP0602. Six ternary phases have been observed and their composition ranges have been determined by EPMA analysis on the annealed alloys. All the binary compounds, excluding Ni₃Sn₄, show a large solubility of the third element. The isothermal section at 873 K, including 17 three phase fields, has been determined.     

The microstructures and mechanical properties of cast Mg–Zn–Al–RE alloys

The microstructures and mechanical properties of cast Mg–Zn–Al–RE alloys with 4 wt.% RE and variable Zn and Al contents were investigated. The results show that the alloys mainly consist of α-Mg, Al₂REZn₂, Al₄RE and τ-Mg₃₂(Al,Zn)₄₉ phases, and a little amount of the β-Mg₁₇Al₁₂ phase will also be formed with certain Zn and Al contents. When increasing the Zn or Al content, the distribution of the Al₂REZn₂ and Al₄RE phases will be changed from cluster to dispersed, and the content of τ-Mg₃₂(Al,Zn)₄₉ phase increased gradually. The distribution of the Al₂REZn₂ and Al₄RE phases, and the content of β- or τ-phase are critical to the mechanical properties of Mg–Zn–Al–RE alloys. The Mg–6Zn–5Al–4RE alloy with cluster Al₂REZn₂ phase and low content of β-phase, exhibits the optimal mechanical properties, and the ultimate tensile strength, yield strength and elongation are 242 MPa, 140 MPa and 6.4% at room temperature, respectively.     

Structural study on Zr0.39Ni0.61 and (Zr0.39Ni0.61)D0.59 amorphous alloys by neutron and X-ray diffraction

Neutron and X-ray diffraction and reverse Monte Carlo (RMC) simulation were performed on Zr_0.39Ni_0.61 and (Zr_0.39Ni_0.61)D_0.59 amorphous alloys to investigate the rearrangement of metal atoms due to the deuterium absorption. The RMC models showed that the Zr–Zr distances slightly increase but the Zr–Ni and Ni–Ni distances remain virtually unchanged after the deuterium absorption. Additionally, the Voronoi polyhedral analysis of the RMC configurations showed that there is not much difference in the local structure around Zr and Ni between Zr_0.39Ni_0.61 and (Zr_0.39Ni_0.61)D_0.59 amorphous alloys.     

Effects of current density and temperature on Sn/Ni interfacial reactions under current stressing

This research studied the electromigration effects on Sn/Ni/Sn sandwich-type couple interfacial reactions with various electric current densities at different temperatures. The Sn/Ni cathode side is always formed with a uniform Ni₃Sn₄ layer. At the opposite Ni/Sn anode interface either Ni₃Sn₄ or NiSn₄ could form, which depends on the reaction temperatures and current densities. The results reveal that with a current density of 1000 A/cm² at 180 °C, the Ni₃Sn₄ phase remains layer-structured. As the applied current exceeds 2000 A/cm², Ni atoms are driven by electromigration force to migrate into the Sn matrix to form the irregular bulk Ni₃Sn₄ and NiSn₄. With a higher current density of 5000 A/cm², large amounts of the Ni₃Sn₄ phase are distributed into the Sn matrix and even the Ni substrate is seriously consumed. At lower temperatures, below 150 °C and with 5000 A/cm² current, the plate-like metastable NiSn₄ phase is found in the Sn matrix at the anode side. In this electromigration study on the Sn/Ni interfacial reactions, both the reaction temperatures and the applied current densities greatly affect the reaction phase species and their morphologies.     

Microstructure and dry sliding wear resistance of laser clad TiC reinforced Ti–Ni–Si intermetallic composite coating

Wear resistant TiC reinforced Ti–Ni–Si intermetallic composite coating with a microstructure consisting of TiC uniformly distributed in Ti₂Ni₃Si–NiTi–Ti₂Ni multi-phase intermetallic matrix was fabricated on a substrate of TA15 titanium alloy by the laser cladding process using TiC/Ti–Ni–Si alloy powders as the precursor materials. Microstructure of the coating was characterized by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray energy dispersive spectrometer (EDS). Dry sliding wear resistance of the laser clad TiC reinforced Ti–Ni–Si intermetallic composite coating was evaluated at room temperature. Results indicated that the TiC/(Ti₂Ni₃Si–NiTi–Ti₂Ni) intermetallic composite coating exhibited excellent abrasive and adhesive wear resistance.