Purpose This study aims to reveals the metallurgical reaction mechanism at the interface between Sn37Pb solder and Ni- x Cu alloy substrates, as well as to explain the reasons for the elevated shear performance of Sn37Pb/Ni-xCu joints, the metallurgical reaction mechanism at the interface between Sn37Pb solder and Ni- x Cu alloy substrates was investigated to find a solution to the problem. This study further reveals the reasons for the elevated shear performance of Sn37Pb/Ni- x Cu joints. Design/methodology/approach The growth behavior of intermetallic compounds (IMCs) at the soldered Sn37Pb/Ni- x Cu ( x = 0, 20, 40, 60, 80 and 100 Wt.%) solid–liquid interface was investigated using electron probe microanalyzer and electron backscatter diffraction, the shear performance of the joints was conducted using a shear tester (MFM1200), following the JESD22-B117 shear testing standard. Findings The results indicated that as the Cu content increased in the Ni- x Cu alloy, the interfacial reactant in the Sn37Pb/Ni- x Cu joints transitioned from the (Ni,Cu) 3 Sn 4 phase ( x = 20 Wt.%) to the (Cu,Ni) 6 Sn 5 phase ( x = 80 Wt.%), effectively circumventing the formation of brittle Cu 3 Sn and Kirkendall voids. It was observed that the thickness of the IMCs layer increased significantly at the Ni matrix with 80 Wt.% Cu. Correspondingly, the (Cu,Ni) 6 Sn 5 grains exhibited a rod-like morphology characterized by [0001] orientation. Notably, this microstructural feature, functioning as a precipitation-strengthening mechanism, markedly enhanced the shear strength to 23.11 MPa. Originality/value The findings of this research could provide valuable theoretical insights into the composition design of microbumps on encapsulated substrates.

In this study, an ultrasonic-electric coupled cladding method was developed to achieve rapid and reliable metallurgical cladding of Sn-0.7Cu solder onto ADC12 Al alloy. Using a coupled field could combine the advantages of both ultrasonic and electric fields. The differences in microstructure, cladding ratios, and mechanical properties of samples between ultrasonic cladding and ultrasonic-electric coupled cladding were compared. Results showed that a diffusion layer composed of alpha-Al, eutectic Si, and Al2Cu phases was formed at the cladding interfaces of both cladding methods. Adding an ultrasonic-electric coupled field could improve cladding efficiency and enhance interfacial reactions. When the substrate was connected to the cathode, the substrate erosion was intensified. The cladding samples prepared using ultrasonic-electric coupled cladding for 1s exhibited the cladding ratio and shear strength of 98.72 % and 16.57 MPa, representing improvements of 43.11 % and 279.17 % compared to those of ultrasonic cladding. The initial oxide film at the cladding interface was rapidly removed under the coupled field, and an amorphous Al2O3 layer was in-situ formed. The enhanced cladding behavior was primarily attributed to the synergistic effects of electrocaloric, cavitation, current accumulation, and Marangoni effects. This study may offer a promising cladding strategy for improving the solderability of Al alloys.

Suppressing solder overflow has significant implications for promoting the application of ultrasonic-assisted soldering. In this work, an innovative strategy of adding metal mesh into Sn-based solder was utilized. 7075 Al alloy joints were ultrasonically soldered with Ni mesh reinforced SAC305 composite solders. The microstructure, bonding ratio, and shear properties of joints were systematically explored. Results showed that solder seams primarily consisted of Ni mesh, SAC305 solder, α-Al phase, Ag3Al2 phase, (Ni, Cu)3Sn4 phase, Al3(Ni, Cu)2 phase, and dispersed fine particles. The bonding interface between Ni mesh and Al substrate could be divided into contact and non-contact regions. A polycrystalline Al3(Ni, Cu)2 phase and a Cu-Al-O amorphous layer were formed at the contact regions. The bonding ratio of joints was mainly affected by the cavitation effects within non-contact regions. Adding Ni meshes could enhance the acoustic pressure and accelerate the flow of local solder in the solder seams. The decrease in the bonding ratio was attributed to the excessive solder flow, which induced the formation of defects. Benefiting from the intrinsic strengthening of Ni mesh and metallurgical reaction strengthening, Al/250#Ni-SAC/Al joints exhibited a shear strength of 71.87 MPa.

This study investigates the influence of RE elements on the room- and high-temperature properties of magnesium alloys. The effects of RE type, addition level, and multi-element alloying strategies were systematically analyzed to clarify the underlying strengthening mechanisms and processing pathways for optimizing Mg–RE alloys. RE elements enhance the mechanical and thermal properties of Mg alloys through crystal structure modification, formation of thermally stable dispersed phases, precipitation strengthening, and solid-solution strengthening. Compared with conventional alloying elements, RE additions offer distinct advantages in strengthening efficiency and overall performance. To fully exploit these benefits, new research paradigms that integrate machine learning and other advanced techniques are required, enabling the intelligent design of multicomponent alloy systems tailored to specific application requirements.

Uniaxial fatigue testing at room temperature was employed to investigate the fatigue characteristics of 7075 high-strength aluminum alloy under very high cycle fatigue (VHCF) conditions across different processing states. Specimens subjected to surface mechanical rolling treatment (SMRT) exhibited smooth and continuous S-N curves, demonstrating three distinct failure modes depending on applied stress amplitudes: surface-induced failure (S-mode), internal crack initiation without fine granular area (FGA) formation (I-mode), and internal failure accompanied by FGA (IFGA-mode). In contrast, welded SMRT specimens and untreated 7075-T651 alloy counterparts displayed only two failure modes (S-mode and IFGA-mode). Notably, fatigue lives in IFGA-mode failure showed processing-independent characteristics across different material conditions. The stress intensity factor range (Delta K) was systematically applied to elucidate the mechanisms underlying these failure mode transitions and the characteristic trends observed in S-N curves.

Achieving reliable bonding is critical for low-temperature active soldering in Al alloys. In this study, a novel Ti-Cu-Ni alloy mesh-reinforced SAC305 composite solder was developed for active soldering of 5A06-Al alloy at 350 degrees C. Effects of soldering time on the microstructure and mechanical properties of joints were investigated, and the interfacial bonding mechanism of joints was analyzed. Results showed that the (Cu, Ni)6 Sn5 phase was formed between alloy mesh and SAC305 solder in the active composite solder, while Ti atoms were uniformly released from the alloy mesh. Metallurgical products within joints mainly comprised (Cu, Ni)6 Sn5 and Al3 (Ni, Cu)2 phases, which developed with increasing soldering time. An amorphous Al2 O3 layer and a Mg-containing layer were formed at the Al substrate/SAC305 solder interface. Mg atoms could enhance the charge transfer between Ti atoms and oxide film, attracting the diffusion of Ti atoms to oxide film. The oxide film removal processes relied on the synergistic impacts of Ti and Mg. The highest shear strength of joints reached 53.21 +/- 0.91 MPa, exceeding previously reported properties for low-temperature active soldering by over 100 %. This exploration may provide insights into developing low-temperature active soldering technologies for Al alloys. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Some unavoidable factors in the operating environment could damage single-crystal components of nickel-based single-crystal superalloys. This work prepared an epitaxial growth NiCoCrAlYTa repaired coating without the columnar-to-equiaxed transition (CET) phenomenon on a nickel-based single-crystal superalloy by electron beam cladding. The microstructure of two cross-sections and two surfaces at different depths were characterized. Moreover, the formation mechanism of coating dendrite was revealed by studying the relationship between coating dendrite size, growth direction, and solidification rate. The microstructure evolution and crystal growth orientation of the coating were investigated. The microstructural investigation of the sample revealed that the dendrites’ orientations on the coating’s horizontal section were different, and its characteristics were highly visible on the surface of the coating. The crystal growth orientations of the coating on the vertical cross-section parallel/perpendicular to the scanning direction of the electron beam were also different. Moreover, the average primary dendrite arm spacing (PDAS) of the columnar dendrite in the different areas of the coating was different and increased from 2 μm to 4 μm. The oxidation resistance of the coating at 1000 °C was about three times higher than that of the substrate.

Metal molecular rings are a class of compounds with aesthetically pleasing symmetry and fundamentally useful properties. The reported work generally focuses on the ring center cavity, and there is little known about those on the ring waist. Herein, we report the discovery of porous aluminum molecular rings and their performance and contribution to the cyanosilylation reaction. We develop a facile ligand induced aggregation and solvent regulation strategy towards AlOC-58NC and AlOC-59NT with high purity, high yield (75% and 70%, respectively) and gram-level scale-up. These molecular rings exhibit a "two-tier" pore feature involving the general central cavity and newly observed equatorial semi-open cavities. AlOC-59NT with two types of one-dimensional channels showed good catalytic activity. The interaction of the aluminum molecular ring catalyst with the substrate has been crystallographically characterized and theoretically confirmed, showing a ring adaptability process that involves the capture and binding of the substrate. This work provides new ideas for the assembly of porous metal molecular rings and to understand the overall reaction pathway involving aldehydes and is expected to inspire the design of low-cost catalysts through structural modifications.

Sapphire and 5A06 Al were ultrasonically soldered with Sn9Zn, SAC305 alloy solders and NiCu alloy foam added Sn-based composite solders, respectively. The microstructure and mechanical properties of joints were investigated and the interfacial bonding mechanism was analyzed. Cracks were observed at the sapphire/Sn matrix interface in joints soldered with alloy solders, which were disappeared in the joints soldered with composite solders. In the joint using NiCu-Sn9Zn composite solder, the solder seam was uneven and Al3Ni intermetallic compound (IMC) layer was formed on the surface of NiCu alloy skeletons. While in the joint using NiCu-SAC305 composite solder, fine particles of (Ni,Zn)3Sn4 were largely formed and homogeneously distributed in the solder seam. An amorphous Al2O3 transition layer was formed at the sapphire/Sn matrix interface, and Zn enrichment was found at the Sn matrix/amorphous Al2O3 interface. The action mechanism of Zn was analyzed by firstprinciples calculation. The joints soldered with NiCu-SAC305 composite solder exhibited the highest shear strength of 74.42 MPa, the shearing failure mainly happened in the soldering seam.

In this study, Ni-Cu/SAC composite solders with different Cu contents were used as an interlayer to solder Al alloy joints at 250 ? for different time. The results showed that the formation and evolution of the mi-crostructure were affected by the Cu contents. In the Ni18Cu/SAC joint, the Sn solder was completely consumed to form a solid-phase joint in 5 min. And (Cu,Ni)(6)Sn-5 was the initial phase formed from the reaction between Sn solder and the Ni18Cu skeleton. Due to the higher Ni concentration than (Cu,Ni)6Sn5 phase in the Ni18Cu skeleton, the Ni atoms diffused from Ni18Cu skeleton to the (Cu,Ni)(6)Sn-5 phase and replaced the Cu atoms in it. As a result, the content of Ni atoms in (Cu,Ni)(6)Sn-5 phase increased continuously, and transformed into (Ni,Cu)(3)Sn-4 at 10 min. Phase transition also occurred in the Ni38Cu/SAC joints. However, the initial phase formed from the reaction between Sn solder and the Ni38Cu skeleton was (Ni,Cu)(3)Sn-4. Therefore, the (Ni,Cu)(3)Sn-4 phase was transformed into (Cu,Ni)(6)Sn(5 )at 10 min because the Cu atoms diffused from Ni38Cu skeleton to (Ni,Cu)(3)Sn-4. On increasing the soldering time, the shear strength of the joints first increased and then decreased, the Ni18Cu/SAC joints soldered for 10 min exhibited the highest shear strength of 58.3 MPa, the shearing failure mainly happened in the composite solder layers. (C) 2022 Published by Elsevier B.V.

In the search for applications for alloys developed under the philosophy of the High Entropy Alloy (HEA)-type materials, the focus may be placed on applications where current alloys also use multiple components, albeit at lower levels than those found in HEAs. One such area, where alloys with complex compositions are already found, is in filler metals used for joining. In soldering (<450 °C) and brazing (>450 °C), filler metal alloys are taken above their liquidus temperature and used to form a metallic bond between two components, which remain both unmelted and largely unchanged throughout the process. These joining methods are widely used in applications from electronics to aerospace and energy, and filler metals are highly diverse, to allow compatibility with a broad range of base materials (including the capability to join ceramics to metals) and a large range of processing temperatures. Here, we review recent developments in filler metals relevant to High Entropy materials, and argue that such alloys merit further exploration to help overcome a number of current challenges that need to be solved for filler metal-based joining methods.

The formation of entrainment defects, (also known as double oxide film defects or bifilms), caused by the entrapment of a doubled-over surface oxide film containing a small amount of local atmosphere, has been investigated by combining practical experiments using a commercial-purity Mg-alloy under protective gases, with theoretical thermodynamic calculations. Evolution of the entrainment defects was studied, and a double-layered structure of their oxide films was found, which was different from the single-layered structure of the Mg-alloy melt surface films that have been previously reported. A pore gas analyzer was used to analyze the gas trapped within the defects from which H 2 and N 2 (from the air) were detected. It was found that entrapped gases can be depleted through reactions with the surrounding liquid Mg-alloy, resulting in the oxide films growing together in the melt. Transformation of the entrained gas to solid-phase compounds could reduce the void volume of the defects, thus probably diminishing the negative effect of the entrainment defects on the quality of castings.

A new High Entropy Alloy (HEA) in the ZnGaCu-(AuSn) system was designed to join skutterudite thermoelectrics (CoSb2.75Sn0.05Te0.20), with a diffusion barrier of Ni applied, to Cu. Such a joint could be part of a device for thermal energy recovery within automotive exhaust systems. A rapid large-scale screening calculation technique based on Python programming has been introduced to conduct the HEA selection process, resulting in a series of alloys, which have been experimentally verified. It is demonstrated that a particular ZnGaCu-(AuSn) HEA alloy can join Ni and Cu successfully; a good joint is formed, and the average electrical contact resistance of the interfaces after joining is promising at room temperature, which shows that it has the potential to improve on the existing fillers used in such applications. The alloy design methodology used here suggests a potential efficient route to design new filler metals for a wide array of applications in which existing filler metals are not suitable.

Nanocomposites of Zr/Nb with exceptionally high hardness were fabricated successfully through the high-pressure torsion (HPT) processing of prepacked Nb/Zr/Nb sandwich samples at ambient temperature. The initial layers of Nb and Zr became fragmented during HPT processing with the formation of many fine-scale intermixed Zr/Nb layers. The intermixing of these Zr/Nb layers increased both with increasing HPT revolutions from 10 to 100 and with increasing radial positions on the disks. The Vickers microhardness, Hv, increased with increasing revolutions and with radial position reaching a maximum of similar to 700 Hv at the edge of the 100 turns sample. Exceptional grain refinement to the range of similar to 20-40 nm and the occurrence of twinning were associated with the HPT-processed Zr/Nb composites after 100 turns. These results suggest a potential route for fabricating high strength bulk Zr/Nb nanocomposites.

Metal matrix nanocomposites were fabricated by high-pressure torsion (HPT) using 5% graphene nanoplates as a reinforcement contained within an Al matrix. Powders were mixed and compacted at room temperature and then processed by HPT at three different temperatures of 298, 373 and 473 K. After processing, microstructural observations were undertaken to reveal the distributions of graphene in the matrix, the grain refinement in the aluminium and the nature of the graphene-aluminium interfaces. Tests were performed to measure the microhardness, the tensile stress-strain curves and the electrical conductivity. The results show that processing by HPT is advantageous because it avoids the sintering and high temperature deformation associated with other processing routes. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd.

功能陶瓷的低温连接一直以来都是电子制造领域的难点.采用超声涂覆工艺实现了ZrO2陶瓷与Sn基焊料的低温连接,并分析了接头的界面连接机理及力学行为.研究结果表明,超声涂覆1200 s后能在ZrO2陶瓷表面包覆均匀Sn镀层,并且在Sn/ZrO2界面形成了ZrSnO4三元相.ZrSnO4相的形成与超声空化效应在Sn/ZrO2界面形成的高温、高压声化学反应环境有关.剪切测试结果表明,ZrO2/Sn/ZrO2接头的剪切强度随超声涂覆时间的延长而不断增加,超声涂覆1200 s时接头的强度达到了32 MPa,剪切失效发生在Sn焊料中.

Ultrasound-assisted dipping of ZrO2 ceramics into molten Sn solder was performed to realize the low-temperature joining of ZrO2 ceramics in this study. Scanning electron microscopy with energy dispersive spectrometer, X-ray diffraction and X-ray photoelectron spectroscopy were employed to study the effects of ultrasonic vibration on the microstructure of Sn/ZrO2 interface, and to elucidate the joining mechanism between Sn coating layer and ZrO2 ceramic. Results showed that, after ultrasonically dipping in molten Sn for 1200s, a pure Sn solder layer with a thickness of approximately 8–9µm was coated on the ZrO2 surface. The Sn coating layer exhibited excellent metallurgic bonding with ZrO2 ceramic. A nano-sized ZrSnO4 ternary phase, which was beneficial to the smooth transition of the lattice from Sn solder to ZrO2 ceramic, was formed at the Sn/ZrO2 interface. The formation of ZrSnO4 interlayer was ascribed to the acoustic cavitation induced high-temperature reaction of Sn, O and ZrO2 at the molten Sn/ZrO2 ceramic interface. The tested average shear strength of ZrO2/Sn/ZrO2 joints was approximately 32MPa, and the shearing failure mainly took place within the Sn solder layer.