Intermetallic Research Articles

Al-clad Cu bond wires for power electronics packaging: microstructure evolution, mechanical performance, and molecular dynamics simulation of diffusion behaviors

With the advancement of power electronics, aluminum-clad copper thick bonding wires have garnered attentions due to superior electrical and thermal properties, making them well-suited for high-temperature and high-current applications. However, the impact remains unveiled of whether the growth of intermetallic compounds (IMCs) at the bonding interface presents critical challenges to the reliability of wedge wire bonds. Therefore, it is necessary to investigate the evolution behavior of Cu/Al IMCs in Al-clad copper wires. In this study, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were firstly employed to characterize the phase composition and growth behavior of Cu/Al intermetallic compounds (IMCs) at two distinct interfaces—the bonding interface and the core-shell interface—under various annealing conditions during high-temperature storage (HTS) tests, revealing a parabolic relationship between aging time and IMC thickness. Subsequently, shear and pull tests of Al-clad copper bond wires were conducted to evaluate the bonding strength under different aging conditions, clarifying the correlation between various failure modes of the bonds and the evolution of IMCs at the bi-interfaces of this novel composite across different aging stages. Additionally, molecular dynamics (MD) simulations were employed to explore the diffusion behavior of Cu and Al atoms. It revealed that polycrystalline structures enhanced the mutual diffusion at the interface, with copper serving as the predominant element in the interdiffusion process. In conclusion, this study integrates experimental and numerical approaches to elucidate the growth mechanisms of Cu/Al intermetallic compounds and their effects on reliability, providing valuable guidance for optimizing the performance of composite bonding wires in high-temperature power device applications.

Effect of post-weld heat treatment on microstructure and mechanical properties of induction roll welded joint for A283GRC steel and 5052 aluminum alloy

Steel-aluminum transition joints are commonly produced through explosive welding and friction welding techniques, serving to link aluminum pressure vessels with steel pipes within cold boxes in air separation unit. This study investigates the impact of PWHT on the microstructure and mechanical properties of steel-aluminum transition joints created via IRW, utilizing A283GRC steel and 5052 aluminum alloy as substrates. The findings suggest that the types of intermetallic compounds (IMCs) in IRW joints remain unchanged before and after heat treatment. The thickness of interfacial IMCs increases with higher annealing temperature and longer annealing time, with a faster growth rate at higher annealing temperatures. After PWHT, the grain size near the interface of the joint on the steel side decreased, with the most significant decrease observed when annealed at 300 °C for 2 hours. While cracks in the interface zone gradually diminish or disappear with PWHT, excessive heat treatment temperature or duration may result in new transverse cracks. At an annealing temperature of 200 °C, there is limited growth range for IMCs and noticeable repair effect on cracks within the interface region. When annealed at 300 °C and 400 °C, there is a decrease in joint hardness compared to before heat treatment levels, and this decreasing rate accelerates with higher annealing temperature and longer duration. Following annealing at 300 °C for 2 hours, the shear strength of the sample reached 70.52 MPa, which is 32% higher than that before heat treatment. Overall findings suggest that the annealing temperature exerts a more pronounced impact on the mechanical properties of joints in comparison to the annealing duration across the investigated time and temperature ranges. The fracture mode exhibited by the samples before and after heat treatment in IRW is characterized by a mixed fracture mode. However, the predominant fracture mode observed without heat treatment is brittle fracture, whereas after heat treatment, ductile fracture becomes the primary mode of fracture.

Quaternary low melting point Sn-Bi-in-xGa solder with improved mechanical performance for advanced electronic packaging

Managing thermal stress is important for ensuring the yield of chip integration and packaging. The development of appropriate low melting point solders has become the key to mitigating thermal stress during the assembling, which aligns well with the demands of next-generation interconnection technologies. In this study, we developed a quaternary low melting point solder based on Sn-Bi-In-xGa (x = 0, 0.1, 0.3, 0.5, 1.0, 1.5, wt%). The addition of Ga not only lowers the solder's melting point but also enhances its wettability. We also studied how the increase of Ga in the solder alloy influences the microstructure and shear test failure mechanism during aging. Upon subjecting solder joints to a 10-min reflow process at 100 °C with Cu substrates, two distinct types of intermetallic compound (IMC) were observed: Cu6(Sn, In)5 when Ga content was ≤0.1 wt% and γ3-Cu9Ga4 when Ga content was ≥0.3 wt%. The stable property of γ3-Cu9Ga4 IMC ensures the mechanical stability of the joints during aging. Therefore, the addition of an appropriate amount of Ga (0.3 wt%) can improve the mechanical performance of solder joints during aging. These findings offer valuable insights for the development of high-performance low-melting-point solders in microelectronics, shedding light on the mechanisms underlying the influence of Ga content on solder microstructures and mechanical reliability during thermal aging.

A strong, ductility maintained, and high-temperature resistant Ti-based composite with TiC@(TiCr2+α-Ti) reinforced particles

While material with light, strong, and high-temperature environment resistant is highly attractive to aeroengines, achieving the combination of all these properties in composite remains a challenge. As these properties typically require the combination of various materials, especially incorporating the extremely brittle intermetallic compound at room temperature into a particle-reinforced composite inherently troubled by the "strength-ductility" contradiction, which can easily exacerbate the inherent brittleness of the material. Herein, we present a composite based on Cr2AlC-Ti system, which generates reinforcements with TiC@(TiCr2+α-Ti) shell-core architecture in the Ti matrix through a straightforward eutectoid reaction. The reinforcements are continuously distributed on a macroscopic level, establishing a co-continuous structure with β-Ti in 3D space. Microscopically, the shell-core structure has a multi-level TiCr2/α-Ti alternating layer structure as in natural nacre. This multi-scale and multi-level structural design overcomes the brittleness of TiCr2 at room temperature by controlling its morphology and distribution, and achieves high content of ceramic particles in composite. The resulting composite has a compressive strength of about 2GPa at room temperature, and even at 600 °C when Ti matrix is completely softened, the composite has a commendable strength of about 800MPa.

Regulatory mechanism of N2 flow rate on structure and properties of CrAlNiYN coatings by FCVA technique

In this work, a novel CrAlNiYN coating was prepared by filter cathode vacuum arc (FCVA) technique. The evolution of the microstructure and properties of the coatings with varying N2 flow rates was systematically investigated. The results revealed that as the N2 flow rate increased from 10 to 90 sccm, the N content in the coating increased from 2.54 to 46.20 at.%, while the Ni content significantly decreased from 67.54 to 31.15 at.%. Simultaneously, the phase structure transitioned from the intermetallic compound AlNi3 to the solid solution Al(Cr)N. This transformation, along with solid solution strengthening and grain refinement, resulted an increase in hardness from 13.4±0.4 to 26.6±0.6 GPa. Moreover, the H/E, H3/E2 and We values also displayed a gradually increasing trend, indicating improved resistance to plastic deformation. However, the adhesion strength presented a weakening trend from HF1 to HF3. Furthermore, the corrosion current density of coatings first increased and then slightly decreased with the increase of N2 flow rate, while the polarization resistance had the opposite trend of change. Among them, the coating at 10 sccm exhibited the best corrosion resistance, with the lowest icorr of 0.150 μA∙cm-2 and the highest Rp of 302.1 kΩ∙cm2.

Hot deformation behavior and hot rolled properties of Gd-rich 316 L austenitic stainless steel neutron shielding material for spent nuclear fuel storage and transportation

Gd-rich austenitic stainless steel as a low-cost neutron shielding structural-functional integrated material is considered the most promising material to replace boron neutron shielding materials. However, as-cast Gd-rich austenitic stainless steel neutron shielding materials are affected by high hardness, low melting point, net-like, brittle intermetallic compound (Fe,Ni,Cr)3Gd, and its hot workability and mechanical properties are very poor. In this paper, Gd-rich 316 L austenitic stainless steel neutron shielding material hot deformation behavior was revealed, and the constitutive equation and hot processing maps were established and verified. On this basis, the effects of hot rolling on material microstructure and properties were studied, mainly discussing the effects of rolling temperature and subsequent solution treatment on the microstructure, recrystallization, mechanical properties, and neutron shielding properties. Studies have shown that Gd-rich 316 L austenitic stainless steel neutron shielding material has good hot workability at deformation temperatures of 950 ∼ 1050 °C and strain rates of 0.01 ∼ 0.1 s−1. Compared with before hot rolling, the strength, elongation and neutron shielding properties of 1050 °C hot-rolled 316 L-2.5wt%Gd neutron shielding material are increased by 1.79 times, 1.96 times and 1.31 times, respectively. After solution treatment at 1100 °C × 60 min, the elongation further increased to 39.53 %, which was 4.32 times than before hot rolling. This study provides valuable insights for high Gd content austenitic stainless steel neutron shielding materials thermo-mechanical processing and improving the strength and plasticity.

Oxynitrided Ti-6Al-4V Coatings Deposited by Twin Wire Arc Spray for Protection of Aluminum Die-Casting Molds

Abstract Steel molds used for aluminum die-casting often fail due to excessive wear or cracking phenomena associated with the soldering effect in contact with molten aluminum, which leads to the formation of iron-based intermetallic compounds and causes problems in the cast components. One solution is to apply protective coatings whose composition is less reactive with the molten aluminum and improve its hardness, toughness, wear, and corrosion resistance, thus prolonging its service life. This work evaluates the effectiveness of Ti-6Al-4V coatings deposited by twin wire arc spraying in an air or nitrogen atmosphere. Nitrogen was used as the carrier and shielding gas for the in-flight molten particles. Coatings were deposited by varying the stand-off distance, the nitrogen gas pressures, and the substrate temperature. The microstructure of the coatings is interlayered, one porous layer of dendrites and one highly densified layer. The presence of TiN, TiO2, α-Ti, and β-Ti phases was confirmed by different characterization methods. For instance, x-ray photoelectron spectroscopy measurements confirmed the presence of N-Ti, O-Ti, and N-O bonds, with the oxygen/nitrogen/titanium percentage associated with the formation of a non-stoichiometric (Ti, Al, V)NxOy phase. Finally, the reactivity of selected oxynitrided Ti-6Al-4V coating in contact with molten aluminum showed a low reaction rate compared to the coarse reaction layer suffered by the uncoated steel substrates.

Preparation of the LiGa Intermetallic Alloy by Electrochemical or Thermal Method for Ammonia Synthesis

Preparation of the LiGa Intermetallic Alloy by Electrochemical or Thermal Method for Ammonia Synthesis

Synthesis and characterisation of Al 7075 – Mg AZ31 alloy bimetal produced by friction stir additive manufacturing with Zn interlayer

ABSTRACT The bimetal formation of Al and Mg alloys has various metallurgical difficulties. To overcome these difficulties, Friction Stir Additive Manufacturing has been suggested as a promising technique for the Al and Mg alloy bimetal formation. In the present work, the defect-free bimetal of Al 7075 and Mg AZ31 alloys with Zn interlayer was successfully synthesised for the first time using Friction Stir Additive Manufacturing at a rotational speed of 1300 rpm and welding speed of 20 mm/min. The intermetallic compounds like MgZn and Mg32(Al, Zn)49 have been observed in the Friction Stir Additive Manufacturing through eutectic reaction at the temperatures 325°C and 330°C, respectively. The maximum strength up to 201 MPa and elongation of 5.4% have been achieved due to the proper mechanical mixing and dynamic recrystallization of material in the stir region. The maximum hardness has been observed in stir region. The hardness increases in top plate (Mg) and decreases in bottom plate (Al) as compared to their base material.

Co-infiltration and dynamic formation of Pd3ZnCx intermetallic carbide by syngas boosting selective hydrogenation of acetylene.

Transition metal carbide shows excellent performance in selective hydrogenation of acetylene, however, the carburization of Pd-based intermetallic compounds remains infeasible. Here we report the successful synthesis of an unprecedented Pd3ZnCx intermetallic carbide, via co-infiltration of zinc and carbon in one-step carburization by syngas. Utilizing state-of-the-art in situ characterizations and theoretical calculation, we unveil the dynamic evolution of Pd3ZnCx during carburization, forming a Pd3Zn like cubic phase carbide structure. A unique transitional state (Pdt) with low content of Zn/C co-infiltration is clearly identified facilitating phase transition and sustain incorporation of carbon and zinc at elevated temperatures. The Pd3ZnCx carbide shows by far the best catalytic performance in the selective hydrogenation of acetylene with a high selectivity (>90%) even at a high H2/C2H2 ratio. Our results therefore provide a co-infiltration strategy and dynamic insights for the one-step synthesis of Pd based intermetallic carbides, towards high-performance intermetallic compound for selective hydrogenation of acetylene.

Drastic enhancement of electronic correlations induced by hydrogen insertion in the cerium intermetallic compound CeFeSi.

We report a comparative study of two cerium-based intermetallic compounds: CeFeSi with an anti-PbFCl type structure, and CeFeSiH with a ZrCuSiAs type structure. The latter is obtained from CeFeSi through hydrogen insertion. Our results are based on X-rays, transport, thermodynamic and magnetic measurements. While the tetragonal structure with P4/nmm symmetry remains unchanged after hydrogen insertion, the thermodynamic, magnetic, and transport properties change drastically. On the one hand, CeFeSi behaves as a Pauli paramagnet with a small Sommerfeld coefficient, indicating the absence of 4f electron physics. On the other hand, our study shows that CeFeSiH exhibits strong magnetic fluctuations with a magnetic transition at 3.5 K, and coherent Kondo-lattice heavy-fermion features.

Exploring alternative manufacturing techniques for high-quality solar cell interconnectors: a comparative study of laser cutting and electric discharge machining

Abstract Solar cell interconnectors are typically crafted from thin foils to establish an electrical connection between two components. For limited production of interconnectors with non-standard dimensions, common production methods (such as stamping and sheet metal processes) cannot be utilized. This article examines alternative techniques, such as Fiber Laser Cutting Machine and Electric Discharge Machining (wire cutting). The laser cutting method did not achieve the desired quality standards, leading to the rejection of the interconnectors. Issues such as burning, local melting, and damage to the silver coating were noted at the edges. The melting of the coating layers formed brittle intermetallic compounds, which can cause cracking and reduce weldability and solderability. In contrast, the Electric Discharge Machining method successfully produces interconnectors with complex shapes by stacking layers of foil. This approach results in high-quality interconnectors that showed no signs of burning or local melting on their edges.

A Nonconventional Method to Produce Zr Alloys to Study the Fe23Zr6 Intermetallic Compound in the Fe-Zr System

A Nonconventional Method to Produce Zr Alloys to Study the Fe23Zr6 Intermetallic Compound in the Fe-Zr System

DFT and Monte Carlo simulations of the intermetallic compound MnZnSb

The present work aims to investigate the structural, magnetic and electronic properties of ternary intermetallic MnZnSb using density functional theory (DFT) and Monte Carlo simulation (MCs). The obtained ground state results reveal that MnZnSb is stable in the ferromagnetic state with a metallic nature and high magnetic anisotropy. The calculated total and local magnetic moments are 2.96 μ B and 3.05 μ B for MnZnSb. Ferromagnetic behaviour was confirmed using the Stoner criterion. The elastic constants are used to verify the mechanical stability of the MnZnSb compound, demonstrating that the compound is mechanically stable and has a brittle character with low Debye temperature. The magnetic behaviour of MnZnSb is studied using MCs and the obtained results show that undergoes a transition from ferromagnetic to paramagnetic state at a critical temperature ( T C ) of 320 K. The computed magnetocaloric effect indicates that the compound exhibits large values of relative cooling power at 14 T, around 502.2 J/K.

Accurate Thermochemistry with Multireference Methods: A Stress Test for Internally Contracted Multireference Coupled-Cluster Theory.

The internally contracted multireference coupled-cluster method with single, double and perturbative triple excitations, icMRCCSD(T), was tested for its performance in the context of computational high-accuracy thermochemistry. The results were gauged against the standard single-reference coupled-cluster hierarchy with up to 5-fold excitations. The test set comprised of a selection of first-row dinuclear compounds and the three 3d-transition metal compounds MnH, FeH, and CoH. The results revealed two problems with the current formulation of icMRCCSD(T). First, the choice of the Dyall Hamiltonian as the zeroth-order Hamiltonian, which leads to a biased description of the different orbital subspaces and particularly poor results for the atomic correlation energies, and second, the tendency to overestimate the perturbative correction for triply excited clusters, in particular in the presence of open shells and correspondingly low orbital-energy gaps. The two problems could be solved by resorting to the effective Fock operator as zeroth-order Hamiltonian and by adopting a modified amplitude equation that includes terms quadratic in the pair clusters. A similar modification was recently proposed by Masios et al. (Phys. Rev. Lett. 2023, 131, 186401) in the context of applying single-reference coupled-cluster theory to systems with small or vanishing band gaps and we chose the acronym '(cT*) correction' in analogy to that work. In contrast to the work of Masios et al., additional terms including single excitation clusters were omitted, as these again lead to an overestimation of correlation effects in more difficult cases. We also tested another alternative for the zeroth-order Hamiltonian and additional higher-order corrections for the correlation energy. These extensions did not significantly improve the results and were also computationally more demanding. The improved icMRCCSD(cT*)F method yields very accurate results with errors, relative to accurate benchmarks, better than 2 kJ/mol for total energies and atomization energies for the entire set of examples considered in this work.

ESI MS Studies of T. Brucei Trypanothione Reductase and its Reactions With Selected Metal Compounds

AbstractTrypanothione reductase from Trypanosoma brucei (TbTR) is a key enzyme of the parasite responsible for human African trypanosomiasis. TbTR catalyzes the reduction of trypanothione, an antioxidant dithiol that protects trypanosomatid parasites from oxidative stress induced by the mammalian host as a defense system. TbTR is considered an attractive target for the development of novel anti‐parasitic drugs because it is essential for parasite survival and has no close homologues in humans. Previous studies have shown that metal compounds can act as potent inhibitors of trypanothione reductase and of related enzymes and may be considered for disease treatment. To better understand the molecular basis of such inhibition, we report the study of the interactions of a small group of metal compounds with TbTR, analyzed by ESI MS measurements. This technique allows direct visualization of the enzyme in solution and the detection and characterization of the metal binding process. Accordingly, TbTR was reacted with a panel of metal compounds including thimerosal, auranofin, its halogen analogues, and bismuth acetate. ESI MS results provide a detailed description of the interactions taking place for each metal compound tested. The implications of these results for the development of novel metal‐based compounds as potential anti‐trypanosomal agents are discussed.

Effects of tool coating and tool wear on the surface and chip morphology in side milling of Ti2AlNb intermetallic alloys

Effects of tool coating and tool wear on the surface and chip morphology in side milling of Ti2AlNb intermetallic alloys

Design of high-performance binary carbonate/hydroxide Ni-based supercapacitors for photo-storage systems

Silicon solar cells were used to convert solar energy into electrical energy, and a supercapacitor was designed to store this energy. To maximize the surface area of the electrodes, a three-dimensional Ni foam substrate was employed, onto which Ni-based compounds were deposited to enhance the electrochemical performance of the electrodes. Specifically, to address the conductivity reduction problem that arises when using only Ni ions, we introduced transition metal ions such as Mn, Co, Cu, Fe, and Zn to create binary compounds as electrode material. These binary metal compounds provided high electronic conductivity, structural stability, and reversible capacity, thereby optimizing the performance of the supercapacitor. As a result, the optimized NiCo(CO3)(OH)2 electrode demonstrated high capacity and excellent cycle stability, exhibiting an energy density of 35.5 Wh kg−1 and a power density of 2555.6 W kg−1 as an asymmetric supercapacitor device. Furthermore, when this device was combined directly with silicon solar cells, it achieved a storage efficiency of 63 % and an overall efficiency of 5.17 % under an illumination intensity of 10 mW cm−2. These findings suggest the potential for commercializing high-performance self-charging energy storage devices and contribute significantly to the advancement of energy storage technology.

Half‐Heusler Alloy CoMnZ (Z = Sb/Sn): Electrode Material for Lithium‐Ion Batteries

ABSTRACTHeusler alloys (HAs) are a well‐known family of compounds generating promising interest due to their robust structure, ease of tailoring their unique properties, and potential applications. The investigations in the direction of the electrochemical performance of these materials as electrodes for rechargeable lithium‐ion batteries (LIBs) have been established theoretically and experimentally. Alloying of alkali metal ions into half‐HAs unit cells can be another route to improve LIBs performance. This work presents our investigations on thermodynamically stable half‐HAs CoMnZ (Z: Sb/Sn) as electrode materials for rechargeable LIBs using the first‐principle calculations based on the density functional theory. The negative formation energies validate the thermodynamic stability of the alloys considered in this study. With increasing Li doping, a structural change from cubic to tetragonal and orthorhombic phase is observed in the host structure, and upon full lithiation (LiMnZ), a cubic structure is attained. The band structure calculations of the host structure and its lithiated phase indicate a metallic nature in these alloys. The calculations are also performed to investigate the structural stability of parent alloys and corresponding lithiated phases. We calculated a storage capacity of around 14.5 Ah/kg for 0.125 atomic fraction of Li atoms, which is increased by nearly 10 times upon full lithiation. A maximum open circuit voltage of around 9.8 V is calculated for Li0.125Co0.875MnSb and CoLi0.125Mn0.875Sb. Thus, all these remarkable results suggest that these intermetallic compounds have a strong potential as the cathode material for LIBs with a robust life and a large capacity.

Ultra-High Activity and Durability of Low-Platinum Fuel Cells Enabled by Encapsulation of L10-PtCo and L12-Pt3Co Intermetallic Compounds.

Developing high-performance, durable, and ultralow-loading platinum (Pt) catalysts for the oxygen reduction reaction (ORR) is crucial for advancing fuel cells. Here, a novel structured alloy catalyst is reported, characterized by Pt-Co intermetallic compounds with a Pt-skin, encapsulated by a covalent organic framework (COF) derived carbon support. This unique structure, combining alloy-induced strain effects and protective encapsulation, leads to exceptional catalytic activity and stability at an ultralow Pt loading of 0.02 mgPt cm-2. To be specific, this catalyst exhibits peak power densities of 1.77W cm-2 in fuel cell tests. It demonstrates a state-of-the-art mass activity of 2.15 A mgPt -1 (@0.9 V), which is 5.38 times that of commercial Pt/C (0.40 A mgPt -1). More importantly, the fuel cell assembled with this novel catalyst displays exceptional durability, with a voltage degradation of only 9.9mV after 100,000 cycles at 0.8 A cm-2 and a mass activity retention of 85% (1.83 A mgPt -1), far exceeding the 2025 initial mass activity (MA) target (0.44 A mgPt -1) of DOE by 4.2 times. Notably, the current density at 0.6 V under hydrogen-air conditions shows only a slight decline after more than 230 h.