Intermetallic Research Articles

Optimization of Ni-Cu binder composition and sintering time for enhanced mechanical properties of Mo alloys via liquid phase sintering

Liquid phase sintering of refractory alloys offers a promising approach to enhance mechanical properties while ensuring cost-effectiveness and near-net shaping capabilities. This study systematically explores the impact of sintering time and Ni-Cu binder composition on densification, shape retention, and mechanical properties of Mo alloys processed via liquid phase sintering. The aim is to identify optimal binder composition and sintering time for low-cost production of dense, near-net-shape Mo alloys with superior mechanical properties. The sinterability of Mo compacts is enhanced as the Ni-Cu ratio increases. However, excessive Ni content induces geometric distortion during sintering. Alloys with Ni-rich binders exhibit two liquids at the sintering temperature, each with differing Mo solubility, resulting in a dual-phase matrix on solidification. Both Cu-rich and Ni-rich binder compositions exhibit brittle δ-MoNi intermetallic compound formation, whose quantity increases with prolonged sintering times. Alloys characterized by low Mo solubility in the matrix, high Mo volume fraction, high Mo grain contiguity, and large dihedral angles demonstrate high structural integrity and resistance to geometric distortion. Conversely, alloys featuring high matrix volume fraction, low grain contiguity, elevated Mo solubility in the binder, and strong Mo-matrix interfaces exhibit enhanced strength, hardness, and ductility. Notably, an alloy with a Ni-Cu ratio of 3:1 sintered for just 30 min at 1420°C demonstrates outstanding mechanical properties—hardness of 410 HV, tensile strength of 920 MPa, and elongation of 9 %—comparable to or better than many previously reported refractory alloys.

Isolation and Diverse Reactivity of an Unsymmetrical 1,2-Bis(silylene)-Stabilized Pentacarbonyl Chromium(0) Species.

The construction of the unsymmetrical 1,2-bis(silylene) pentacarbonyl chromium(0) complex 1 was achieved through the reaction of chlorosilylene with half an equivalent of K2Cr(CO)5. X-ray diffraction analysis of 1 confirms the formation of the Si-Si bond and the coordination of one of the silicon atoms to the Cr center. Density functional theory (DFT) calculations disclose that highest occupied molecular orbital (HOMO) mainly corresponds to the lone pair of electrons on the silicon atom and the σ-bonding interaction between two Si atoms. Based on its unique electronic structure, its diverse reactivity toward the transition metal compounds and small molecules was investigated in detail. The reactions of 1 with Fe2(CO)9 or CuCl yielded the 1,2-bis(silylene)-stabilized heterobimetallic complex 2 or oxidized product 3, respectively. Additionally, treatments of 1 with selenium, CO2, or Me3SiN3 led to the formation of the corresponding selenium-, oxo-, and nitrogen-bridged complexes 4-7. All compounds were characterized by multinuclear NMR spectroscopy and X-ray crystallography.

Lifetime prediction of copper pillar bumps based on fatigue crack propagation

2.5D package realizes the interconnection of multiple dies through Si interposers, which can greatly improve the data transmission rate between dies. However, its multi-layer structure and high package density also place higher reliability requirements on the interconnection structure. As a key structure for interconnection, copper pillar bump (CPB) has small size, high heat generation, and thermal mismatch with silicon chips. The thermal fatigue failure of CPB has gradually become the main failure mode in 2.5D package. Due to the small size of CPB and the large proportion of intermetallic compound (IMC) layers, the lifetime prediction method of spherical solder joints is no longer suitable for CPB. Therefore, it is necessary to establish a fatigue lifetime prediction method for CPB. This paper establishes a method for obtaining the lifetime of CPB based on the basic theory of fatigue crack propagation. Using the extended finite element simulation method, the crack propagation lifetime of CPB under thermal cycling was obtained, and the influence of different IMC layer thickness on the fatigue lifetime of CPB was analyzed. The results indicated that the fatigue lifetime of cracks propagating in the IMC layer is lower than that of cracks propagating in the solder layer, and an increase in the thickness of the IMC layer leads to a significant decrease in the fatigue lifetime of CPB. The lifetime prediction method for CPB proposed in this paper can be used for reliability evaluation of 2.5D package, and has certain reference value for the study of the lifetime of CPB.

A comprehensive study on dry sliding wear and in-vitro degradation of AZ31 composite with 6 wt% Sn and 1.5 wt% TiO2 fabricated by stir casting

Abstract This experimental study investigates the dry sliding wear behaviour of novel AZ31 composite with 6 wt% Sn and 1.5 wt% TiO2 samples, focusing on the influence of sliding distance and normal load. Additionally, the research examines degradation rates during a 120-hour immersion period in simulated body fluid (SBF). The wear volume loss increased significantly with higher loads and longer sliding distances, showing a 142% rise from 1000 m to 2000 m and 76% from 2000 m to 3000 m under a 5 N load, peaking at a 25 N load over 5000 m. The specific wear rate dropped by 39% from 5 N to 15 N but increased with distance due to thermal softening, while the coefficient of friction decreased from 0.284 at 1000 m to 0.213 at 5000 m under 5 N. FESEM analysis revealed a transition from abrasive to delamination wear, with a protective oxide layer forming during sliding. Sn in the composite formed hard Mg2Sn intermetallic compounds, affecting crack formation and propagation under higher loads. Wear debris analysis showed both abrasive and delamination wear mechanisms, highlighting the protective role of the oxide layer. The degradation rate increased rapidly during the initial immersion stage in simulated body fluid (SBF), reaching 15.9 mm year−1 after 24 h, and then stabilizing after 48 h. Hydrogen evolution rose sharply from 0.28 ml cm−12 at 2 h to 7.6 ml cm−12 within 24 h, with a 92% increase by 48 h and an additional 38% increase from 48 to 72 h. Post-immersion FESEM analysis showed corroded surfaces with protective layers, cracks, and pitting corrosion. Magnesium hydroxide (Mg(OH)2) and hydroxyapatite played crucial roles in inhibiting corrosion. This analysis provides insights into the wear, and degradation dynamics of the AZ31-6Sn/1.5TiO2 composite, with implications for engineering applications and the development of biodegradable implants in biomedical fields.

A Study on the Effect of Pd Layer Thickness on the Properties of Cu-Ag Intermetallic Compounds at the Bonding Interface.

This paper conducted a high-temperature storage test (HTST) on bonded samples made of Pd100 (Pd-coated Cu wire with a Pd layer thickness of 100 nm) and Pd120, and studied the growth law of Cu-Ag intermetallic compounds and the inhibitory mechanism of Pd thickness on Cu-Ag intermetallic compounds. The results show that the Kirkendall effect at the bonding interface of the Pd100-bonded sample is more obvious after the HTST, the sizes of voids and cracks are larger, and the thickness of intermetallic compounds is uneven. But, the bonding interface of the Pd120-bonded sample has almost no microcracks, the Kirkendall voids are small, and the intermetallic compound size is uniform and relatively thin. The formation sequence of intermetallic compounds is as follows: Cu atoms diffuse into the Ag layer to form Ag-rich compounds such as CuAg4 or CuAg2, and then the CuAg forms with the increase in diffused Cu elements. Pd can significantly reduce the Kirkendall effect and slow down the growth of Cu-Ag intermetallic compounds. The growth rate of intermetallic compounds is too fast when the Cu bonding wire has a thin Pd layer, which results in holes and microcracks in the bonding interface and lead to the peeling of the bonding interface. Voids and cracks will hinder the continuous diffusion of Cu and Ag atoms, resulting in the growth of intermetallic compounds being inhibited.

Improved strength and interfacial microstructure of dissimilar Al/steel weld via combined addition of Zn and Ni

The effect of the combined addition of Zn and Ni on the mechanical properties and microstructures of an intermetallic compound (IMC) layer of dissimilar welds of Al alloy 5052 to low-carbon steel was systematically investigated. A maximum weld strength of 120 MPa was achieved with the combined addition of Zn and Ni, which was 193 % higher than that of the weld produced without the addition of Zn or Ni. The addition of Zn resulted in the formation of soft Fe–Zn IMCs in the IMC layer, which reduced the hardness of the IMC layer. Additionally, the combined addition of Zn and Ni promoted the formation of Fe–Zn IMCs, which further softened the IMC layer. Further softening of the IMC layer, reduction in the thickness of the IMC layer, and suppression of the formation of defects in the IMC layer, achieved by the combined addition of Zn and Ni, drastically improved the weld strength.

Synergistically enhanced ORR and HER performance on Co-N-C coupled in-situ generated PtCo intermetallic

Integrating multi-scale sites in a composite catalyst is vital to realize efficient electrocatalysis. Herein, a synergistic composite catalyst consisting of Co atomic sites and in-situ generated PtCo intermetallic compounds (IMCs) (o-PtCo@CoNC) is proposed through Co pre-anchoring and subsequent impregnation-reduction method. High loading of Co atoms provides a chance for in-situ generating PtCo ordered intermetallic compounds. The remaining Co single atoms and PtCo IMCs construct synergistic electrocatalytic micro-regions. Benefiting from the ordered structure, synergistic effect of PtCo IMCs and Co single atoms, o-PtCo@CoNC exhibits excellent electrocatalytic performance for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) with mass activity of 1.21 A mgPt−1 (at 0.9 V) and 5.70 A mgPt−1 (at an overpotential of 100 mV), respectively. Besides, o-PtCo@CoNC delivers negligible loss of half-wave potential and overpotential during long-term stability test in acid solutions, with 13 mV decay after 50,000 potential cycles for ORR and a 2.7 mV decay after 20,000 potential cycles for HER. The integration strategy of single-atomic sites coupled IMCs paves the way for enhancing the activity and durability of Pt-based electrocatalysts.

Diffusion and marker experiments for the newly discovered CuIn2 compound

Herein, CuIn2 is not identified as a stable phase in the CuIn binary phase diagram. However, several studies have reported the existence of CuIn2 at low temperatures. In this study, an electroplating process was used to examine the solid-state interfacial reactions between indium and copper. An indium layer with a thickness of 50 μm was electroplated onto a 1 mm thick Cu substrate at 25 °C, and the resultant Cu/In diffusion couples were subjected to aging processes at 60 °C, 80 °C, 100 °C, and 120 °C for up to 1000 h. These findings indicate that both CuIn2 and Cu11In9 phases were formed at 60 °C, 80 °C, and 100 °C, whereas only the Cu11In9 phase was detected at 120 °C. The growth kinetics of the Cu/In intermetallic compounds adhered to a parabolic law, implying that the reactions were governed by diffusion-controlled mechanisms. The utilization of a Ta diffusion marker in the experiments revealed that indium acts as the predominant diffusing species within the CuIn2 intermetallic compound.

Prediction of Sm- (Co, Cu, Fe, Zr) binary alloys’ thermodynamic parameters by improved miedema model

Abstract At present, the calculation results of the original Miedema mixing enthalpy model are still somewhat different from the experimental results. Therefore, it is necessary to improve the calculation accuracy of the Miedema model to promote the development of the Miedema model and its application in the design of samarium-cobalt permanent magnet alloys. To solve this problem, the enthalpies of mixing of Sm- (Co, Cu, Fe, Zr) binary alloys were calculated in this paper by using the modified model. The mixing enthalpy (DH), excess entropy (SE), excess Gibbs free energy (GE), component activity (α) and binary Gibbs free energy of Sm-Co, Sm-Fe were calculated. The results show that the improved Miedema model can better match the experimental values. Sm- (Co, Fe, Cu) binary alloys are easy to generate intermetallic compounds. And Sm-Zr is difficult to form intermetallic compounds. The DH, SE and GE of Sm- (Co, Fe) are negative, and there is a large negative deviation from Raoult's law for the activity of each component compared to the ideal solution. The Gibbs free energies for both SmCo5 and Sm2Co17 precipitation reactions are less than zero in the temperature range between 1550 and 1620 K. The Sm2Co17 phase is thermodynamically more stable than the SmCo5 phase.

Fracture strain improving via structural austenitic stainless steel-coated 22MnB5 plates

A total of 316 austenitic stainless steel (ASS) coatings were deposited on 22MnB5 press-hardening steel plates by varying the substrate bias voltages using a magnetron sputtering technique and quenched in a flat mold with cooling water. The substrate bias current and ion-bombardment energy densities increased up to 0.5 mA/mm2 and 50 J/mm2 at a high voltage of −100 V, and, therefore, the variations in the coatings’ morphologies were owing to the increases in the ion bombardment. The porous bulk pattern appeared in the quenched ASS coating at −100 V, clearly different from the porous columnar structure of the others at −50 and −75 V. The γ-Fe and α-Fe phases were observed from the diffraction peaks, presented the ASS coating and 22MnB5 substrate, respectively. There was no intermetallic compound (IMC) peak detected. In addition, the diffusion layer of the quenched ASS-coated plate was observed, in which its morphology was different from the quenched martensite (M) plate, and proved to be the α-Fe microstructure by the very low α-Fe peak at the standard (110) position. The bright image of TEM and the select area electron diffraction pattern indicated the nanostructure of the quenched ASS coating. The nanohardness of the ASS coating, diffusion layer, and M plate (7.36, 3.60, and 6.25 GPa, respectively) was detected, indirectly proving an α-Fe structure of the diffusion layer. The fracture angles of the 316-coated plates significantly improved from 51.82° at −50 V, 53.77° at −75 V to 57.38° at −100 V, as the ASS structure changed to be porous bulk pattern. The clearance of IMC, coating’s porous bulk pattern, and the low hardness α-Fe diffusion layer benefited for the fracture strain by lengthening the pathway of the crack’s development and blocking the further crack’s propagation, respectively.

Development of novel Gd-Fe/Ti composites with tunable thermal expansion property

Abstract Titanium alloys are considered one of the most promising materials. However, their poor thermal expansion property remains a major obstacle to their widespread application. In this study, we explored an innovative design strategy to tune the thermal expansion properties of titanium alloy. Specifically, we used rare earth iron intermetallic compounds (Gd-Fe IMCs) with low coefficient of thermal expansion (CTE) as expansion inhibitors to prepare composites with the required thermal expansion properties via in situ reaction. The morphology and size of Gd-Fe IMCs can be effectively controlled by electromagnetic and ultrasonic fields, resulting in a dense distribution of micro/nano-structured Gd-Fe IMCs and strong interfacial bonding of the composites. This alloy has an excellent CTE of 6.8 × 10−6/K and a high ultimate tensile strength of 921 MPa. The improvement in the physical properties (especially in thermal expansion properties) of titanium alloy can be attributed to the synergistic effect between Gd-Fe IMCs and Ti matrix. This design strategy can also be extended to other titanium alloys as a reference for designing low thermal expansion titanium alloys.

N-doped carbon confined ternary Pt2NiCo intermetallics for efficient oxygen reduction reaction

Developing high performance electrocatalysts for the cathodic oxygen reduction reaction (ORR) is essential for the widespread application of fuel cells. Herein, a promising Pt2NiCo atomic ordered ternary intermetallic compound with N-doped carbon layer coating (o-Pt2NiCo@NC) has been synthesized via a facile method and applied in acidic ORR. The confinement effect provided by the carbon layer not only inhibits the agglomeration and sintering of intermetallic nanoparticles during high temperature process but also provides adequate protection for the nanoparticles, mitigating the aggregation, detachment and poisoning of nanoparticles during the electrochemical process. As a result, the o-Pt2NiCo@NC demonstrates a mass activity (MA) and specific activity (SA) of 0.65 A/mgPt and 1.41 mA/cmPt2 in 0.1 mol/L HClO4, respectively. In addition, after 30,000 potential cycles from 0.6 V to 1.0 V, the MA of o-Pt2NiCo@NC shows much lower decrease than the disordered Pt2NiCo alloy and Pt/C. Even cycling at high potential cycles of 1.5 V for 10,000 cycles, the MA still retains ∼70%, demonstrating superior long-term durability. Furthermore, the o-Pt2NiCo@NC also exhibits strong tolerance to CO, SOx, and POx molecules in toxicity tolerance tests. The strategy in this work provides a novel insight for the development of ORR catalysts with high catalytic activity, durability and toxicity tolerance.

Efficient Catalysts Based on Substitutional Solid Solutions and Palladium Intermetallic Compounds for the Selective Hydrogenation of Acetylene to Ethylene

Efficient Catalysts Based on Substitutional Solid Solutions and Palladium Intermetallic Compounds for the Selective Hydrogenation of Acetylene to Ethylene

The Evolution of Interfacial Intermetallic Compound Growth and Solder Joint Strength of Sn-40Pb/Cu under Thermal Aging

The Evolution of Interfacial Intermetallic Compound Growth and Solder Joint Strength of Sn-40Pb/Cu under Thermal Aging

Predictive modeling of MRR, TWR, and SR in spark-EDM of Al-4.5Cu–SiC using ANN and GEP

In this study, Al-4.5Cu alloy was reinforced with varying weight percentages of SiC particles (2%, 4%, 6%, and 8%) to create metal matrix composites via the stir casting method. The formation of intermetallic compounds was confirmed through energy dispersive spectroscopy and x-ray diffraction analysis. This article compares the performance of Artificial Neural Network (ANN) and Gene Expression Programming (GEP) models in predicting the Metal Removal Rate (MRR), tool wear rate, and surface roughness in the die-sinking electro-discharge machining (EDM) process of the ex-situ developed Al-4.5%Cu–SiC composites. The study considers three machine parameters—pulse on time (TON), pulse off time (TOFF), and current (I)—along with the weight fraction of SiC particles as input variables for the models. Both ANN and GEP models demonstrated high predictive accuracy for the EDM performance metrics, with correlation coefficients (R) ranging from 0.973 68 to 0.980 65 for the ANN model and 0.980 11 to 0.982 59 for the GEP model. Notably, the GEP model exhibited superior predictive capability, as evidenced by its higher correlation coefficients and lower root mean square error, indicating greater effectiveness in predicting the EDM process outcomes than the ANN model.

Sustainable catalytic pathways for biofuel precursors: quantitative conversion of glucose to gluconic acid using Pt-Zn biochar catalyst

Achieving quantitative conversion of biomass-derived feedstocks under ambient environmental conditions (20°C, atmospheric air, 0.1 MPa) is a critical milestone for sustainability in chemical processes. Herein, the quantitative conversion of glucose to gluconic acid was accomplished under ambient environmental conditions without any additives using a Pt-Zn intermetallic nanoparticle-supported biochar catalyst prepared from raw rice straw (Pt-Zn/strawC) via a straightforward one-pot solvothermal reaction with ethylene glycol solvent. Spectroscopic analyses verified the formation of the Pt-Zn intermetallic alloy and confirmed strong electronic metal-support interactions. The Pt-Zn/strawC catalyst (Pt:Zn molar ratio of 1:6) was highly selective for the conversion of glucose to gluconic acid, whereas yields as high as 99.9% (98.9% gluconic acid, 1.0% glucaric acid) were reached at 20 oC under base-free and additive-free conditions. Isotope measurements and density functional theory revealed synergistic interactions in the Pt-Zn alloy, wherein the alloy tended to absorb glucose and active O2 into superoxide radical (O2·). This work demonstrates a chemocatalytic method that is practical for environmental conditions and provides a new avenue for sustainable conversion of lignocellulosic biomass to chemical products.

Lanthanides in the water electrolysis

AbstractThe most feasible technique for producing green hydrogen is water electrolysis. In recent years, there has been significant study conducted on the use of transition metal compounds as electrocatalysts for both anodes and cathodes. Peoples have attempted several strategies to improve the electrocatalytic activity of their original structure. One such technique involves introducing rare earth metals or creating heterostructures with compounds based on rare earth metals. The incorporation of rare earth metals significantly enhances the activity by many folds, while their compounds offer structural stability and the ability to manipulate the electronic properties of the original system. These factors have led to a recent boom in investigations on rare earth metal‐based electrocatalysts. There is currently a pressing demand for a review article that can provide a comprehensive overview of the scientific advancements and elucidate the mechanistic aspects of the impact of lanthanide doping. This review begins by explaining the electronic structure of the lanthanides. We next examine the mechanistic aspects, followed by recent advancements in lanthanide doping and heterostructure formation for water electrolysis applications. It is expected that this particular effort will benefit a broad audience and stimulate more research in this area of interest.image

Phase composition and microstructure of intermetallic alloys obtained using electron-beam additive manufacturing

The paper investigates the microstructure and phase composition of nickel- and aluminum-based intermetallic alloys obtained using two-wire electron-beam additive manufacturing (EBAM). Relevance of the research is related to the widespread use of intermetallic alloys based on nickel and aluminum (mainly Ni3Al) in various high-temperature applications and the need to use modern production methods when creating machine parts and mechanisms from these alloys. Using EBAM, the billets from intermetallic alloys with different ratios of the content of main components were obtained. Change in concentrations of the basic elements was carried out varying the ratio of feed rates of nickel and aluminum wires during additive manufacturing in the range from 1:1 to 3:1, respectively. The results of microscopic studies of the obtained alloys showed that, regardless of nickel content, the obtained alloys are characterized by a large–crystalline structure with grain sizes in the range of 100 – 300 μm for alloys with a component ratio of 1:1 and 150 – 400 μm for alloys with a component ratio of 2:1 and 3:1. At the same time, the alloy with an equal content of base components is characterized by more uniform grain and microstructure compared to those with high content of Ni. By changing the concentration ratio of the components, phase composition of the resulting billet can be purposefully controlled. In the case of an “equiatomic” content of the base components in the alloy, a NiAl-based compound with a small phase content based on the intermetallides Ni3Al5 and Ni3Al is formed. At high concent­rations of nickel, the intermetallic Ni3Al phase is formed, and at a component ratio of 3:1, structure of the resulting billet consists mainly of Ni3Al phase and the γ solid substitutional solution based on nickel. The paper demonstrates the possibility of direct production of intermetallic alloys with a given phase composition during electron-beam additive manufacturing.

Microstructure and shear properties of interconnect interface between multi-phase heterogeneous SnBi eutectic alloy and Cu substrate

The microstructures of the interconnect interfaces between Sn58Bi eutectic alloy and Sn53Bi3Cu3Zn2Ag2Sb multiphase alloy and Cu substrate, as well as the strength of the interconnect joints were systematically studied after 1008 h thermal aging at 70℃. Compared with the unmodified Sn58Bi alloy, the addition of alloying elements inhibited the coarsening of the organization and the growth of intermetallic compound (IMC) at the interconnect interface. At the same time, the Cu3(Sn, Zn) phase in the upper part of the IMC and twinned Cu in the substrate can contribute to enhanced the mechanical properties of the interconnect joints. Compared to their respective shear strengths after reflow, the strength of the modified Sn53Bi3Cu3Zn2Ag2Sb/Cu interconnect joints increased by 22.3 %, while the strength of the Sn58Bi/Cu interconnect joints decreased by 18.3 % after thermal aging. This study indicate that alloying modification can effectively improve the shear strength of interconnect joints during aging, thus improving interconnect reliability.

Effect of annealing temperature on interface diffusion behavior of ultra-thin Cu/Al composite sheet by secondary micro-rolling

In this paper, the effect of different annealing temperatures on the interface diffusion behavior of ultra-thin Cu/Al composite sheets was studied. The ultra-thin Cu/Al composite sheet of 0.04 mm was successfully prepared by micro-rolling. The results show that with the increase of annealing temperature, the thickness of diffusion layer increases and the grain size of Cu and Al increases, the interface diffusion of Cu/Al becomes more sufficient. Comparison of diffusion layer thickness between secondary micro-rolling ultra-thin Cu/Al composite sheet and primary micro-rolling ultra-thin Cu/Al composite sheet at the same annealing temperature, the thickness of the interface diffusion layer decreases at the annealing temperature of 360℃ and 400℃, but increases at the annealing temperature of 440℃. The intermetallic compounds CuAl2, Cu4Al and Cu9Al4 are formed at the annealing temperature of 360, 400 and 440℃ after primary micro-rolling ultra-thin Cu/Al composite sheet. Intermetallic compounds CuAl2, Cu4Al and Cu9Al4 were formed at the annealing temperature of 360℃, and intermetallic compounds CuAl2, Cu4Al, Cu9Al4 and CuAl were formed at at the annealing temperature of 400℃ and 440℃ after secondary micro-rolling of ultra-thin Cu/Al composite sheet.