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A continuum mechanics approach to cold welding (CW) of metals under shear is considered. The main idea is to treat a weld joint as an extra material—a "third body" in its own right. Its properties stem from plastic co‐deformation of the two contacting alloys. The mechanical characteristics of the weld joint, i.e., its strength and plasticity in the complex stress state, are determined by the deformation history of the "third body." The proposed approach enables a unified description of the CW process itself, as well as the subsequent variation of shape of the composite material with the weld joint. [ABSTRACT FROM AUTHOR]

The need to modify removable partial dentures equipped with a metal framework in order to add other prosthetic teeth to replace natural teeth lost by the patient could lead to laboratory procedures so complex as to require the creation of new prostheses with a heavy economic burden. The creation of preformed metal pins to be welded using the economical TIG cold welding method could represent a valid alternative solution with the aim of modifying the prostheses using a reinforced resin capable of adequately resisting masticatory loads. This study evaluates and compares the mechanical robustness and the clinical reliability of these modified prostheses in cases of junctions of one or two contiguous prosthetic teeth. The 6-month follow-up demonstrated the total validity of the method via the absence of significant breakages or detachments in all of the patients analyzed; on the other hand, the prostheses modified using the traditional method and used as controls showed a high incidence of fractures. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the retention force of a novel conometric system after thermomechanical aging. In addition, the conometric system's retention force was compared with that of the cemented implant‐retained crowns. Materials and methods: Two systems to retain implant crowns were tested in this study: a conometric system and a cement‐retained system. Forty‐eight zirconia crowns were fabricated using computer‐aided design and computer‐aided manufacturing technology. Twenty‐four zirconia crowns were cemented onto conometric caps with resin‐modified glass ionomer cement, which were then connected with abutments. These specimens were divided into three groups, and each group was subjected to the pull‐out test. A‐control group: 12 specimens directly subjected to pull‐out test; A‐aged group: 12 specimens subjected to thermomechanical aging followed by pull‐out test; A‐repeat group: After the pull‐out, the specimens in the aging group (A‐aged) were reconnected, and the pull‐out test was repeated once more. The remaining 24 zirconia crowns were cemented on standard abutments with zinc phosphate cement, and two groups were formed. C‐control group: 12 specimens directly subjected to the pull‐out test; C‐aged group: 12 specimens subjected to thermomechanical aging followed by pull‐out. Scanning electron microscope (SEM) was used to evaluate the surfaces of caps and abutments. To analyze the data, repeated measures, one‐way ANOVA, and Bonferroni tests were used (p < 0.05). Results: The mean retention force value of the A‐control group was 148.22 ± 16.37 N. The highest mean retention force value was measured in the A‐aged group (204.93 ± 51.67 N), and the lowest mean retention force value was seen in the A‐repeated group (77.02 ± 21.48 N). Thermomechanical aging had a significant influence (p < 0.05) on both systems. No significant differences in retention force were found between the thermomechanical aged groups of both systems (p > 0.05). SEM analysis revealed that aging had an impact on the surface of the conometric system's caps and abutments. Conclusions: The retention force of the conometric system increased significantly following thermomechanical aging. No crown separation occurred during the thermomechanical aging of the conometric system. There was no significant difference in the retention of the conometric and cemented systems after thermomechanical aging. [ABSTRACT FROM AUTHOR]

Developing ultra-high-density interconnects using current technologies presents certain limitations. It is because traditional solder joint technology employs a liquid-solid interfacial reaction process that makes it difficult to control the shape of the solder joint, thus limiting the size, pitch, and density of interconnects. Although the Cu–Cu direct bonding technique can help fabricate high-density interconnects, its high cost and limited application in consumer electronics present further challenges. In this study, we developed a simple, rapid, and cost-efficient method for fabricating high-density interconnects. We produced homogeneous submicron solder particles as small as 300 nm through ultrasonic treatment. The homogeneous size distribution was achieved by minimizing inter-particle ripening reactions, sluggish diffusion, and low Gibbs-Thomson chemical potential in the medium-entropy Sn–Bi–In-based solder particles. We dispensed the particle solution between two Cu substrates, and they bonded within 5 min at room temperature through a solid-state interfacial reaction. The shear strength of the bonding is around 14.8 ± 1.2 MPa. Our bonding technology shows potential for use in 3D integration to manufacture ultra-high-density interconnects.

Cold welding at the nanoscale is a promising technique for bottom‐up fabrication and assembly of nanostructured materials. Herein, the cold welding process of the CoCrFeCuNi high‐entropy‐alloy (HEA) nanowires in the form of side‐by‐side contact using molecular dynamics simulation is inestigated. The effects of overlap length, crystal orientation, and temperature are taken into consideration. The results demonstrate that strength is positively correlated with the overlap length. Fracture strain first increases up to a maximum and then decreases with the increase in overlap length. When the temperature increases from 300 to 900 K, the ultimate stress of the welded nanowires decreases from 1.18 to 0.87 GPa, and the welding stress decreases from −0.54 to −0.26 GPa. The crystal orientation significantly influences the deformation mechanism. For samples welded by nanowires with the same crystal orientation, the primary deformation mechanisms are twinning and dislocation slip. However, for samples welded by nanowires with different crystal orientations, the deformation is primarily mediated by the grain boundary slip. The research can enhance the understanding of the cold welding behavior for low‐dimensional materials and is hopeful to provide some valuable guidance for the bottom‐up fabrication and assembly of HEA nanocomponents. [ABSTRACT FROM AUTHOR]

To investigate the influence of rotation speed and milling time on the formation of nickel (Ni) coatings prepared by mechanical coating technique (MCT), the Ni metal powders and the zirconia (ZrO2) ceramic balls were used as the coating materials and the substrates to fabricate the Ni coatings. The thickness of the coatings was characterized by the weight increase of the ZrO2 balls after the coating operation, and the microstructure and composition of the coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). In the results, with the increase of rotational speed, the coatings thickness increases at the initial stage of ball milling and decreases at the later stage. The coatings thickness reaches the maximum (20 μm) when the rotation speed is 240 r∙min‒1 for 15 h. The formation of Ni coatings consists of two stages as thickening and thinning, which is affected by the rotation speed. The higher rotation speed is favor of the coatings formation and improves the processing efficiency, while the excessively speed will accelerate the coatings to peel off from the substrate, which is unfavorable to the formation of the coatings.

This work focuses on the synthesize of nanostructured (Fe65Co35)100-x (Pr6O11)x (x = 0, 5) powders using high energy ball milling. The influence of Pr6O11 on structural, morphological and magnetic properties of Fe65Co35 nanoparticles were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) with a dispersive energy analyzer (EDS), vibratory sample magnetometer (VSM) and differential scanning calorimetry (DSC). Results show that the praseodymium oxide addition increased the decrement rate of the crystallite size with milling time of about 27 % and decreased the increment rate of the internal micro-strain of 50 %. Moreover, because of its high grain fragmentation tendency, Pr6O11 increases the hardness and brittleness of Fe-Co powders. Moreover, it minimized the cold welding between Fe-Co ductile particles leading to a significant decrease in the average particle size (~1�m). The magnetic measurements conducted at room temperature show that the saturation magnetisation (Ms) and the coercivity (Hc) increased with milling time in both compositions. A low Ms and high Hc values were detected in (Fe65Co35)95 (Pr6O11)5 nanoparticles. The results demonstrated a soft ferromagnetic nature in all of the synthesized nanoparticles with Ms in the range 207 � 216 emu/g and Hc is found to be 113 Oe.

Cold welding of metals at the nanoscale has been demonstrated to play a significant role in bottom-up manufacturing and self-healing processes of nanostructures and nanodevices. However, the welding mechanism at the nanoscale is not well understood. In this study, a comprehensive demonstration of the cold welding process of gold nanorods with different modes is presented through in situ liquid cell transmission electron microscopy. The experimental results and molecular dynamics simulations reveal that the nanorods are welded through the facet-dependent atomic surface diffusion and rearrangement along {100} facets. The density functional theory calculations indicate that the preferred coalescence of two {100} surfaces is thermodynamically favorable. Unlike the prevalent "oriented attachment" in the nanoparticle coalescence, the misalignment of nanorod orientations and local stresses can induce grain boundaries and stacking faults in the welded interface., (© 2025 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

The Ni coatings were prepared from nickel metal powder and zirconia ceramic balls by mechanical coating technique. The relationship between rotation speed and coatings thickness was studied, the thickness of the coatings was characterized by the weight increase of the zirconia balls after mechanical coating. The composition and microstructure of the coatings with maximum thickness were analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray Diffraction (XRD). The results revealed that the formation of coatings consists of thickening from the cold welding between Ni particles and the thinning from the exfoliation of coatings work hardening. The thickness of the coatings reaches the maximum when the above two process progress are close to each other. The results proved that higher speed was favor of the coatings formation, the maximum thickness was obtained at the 15 h for rotation speed of 240 rpm, and microscopic images show that the average thickness was about 20 μm.

Cold welding is one of the mechanical complications of dental implants. This case report describes how a cold welded gingival former was successfully retrieved without damaging the threads using combination of ultrasonic scaler, surgical screw driver and a gingival retraction cord. This is a simple, cost-effective technique that can be adopted in all dental implant systems. [ABSTRACT FROM AUTHOR]

Cold-welding possesses such desirable environment as low temperature and low applied stress, thus becoming the prime candidate for nanojointing and nanoassembly techniques. To explore the welding mechanism of nanoscale structures, here, molecular dynamics was performed on copper nanowires under different welding conditions and various original characteristics to obtain an atomic-level depiction of their cold-welding behavior. By analyzing the mechanical properties of as-welded nanowires, the relations between welding quality and welding variables are revealed and identified. This comparison study will be of great importance to future mechanical processing and structural assembly of metallic nanowires. [ABSTRACT FROM AUTHOR]

Space Debris is a major problem posing a great threat to all the future space travels as well as to all the satellites which are orbiting around the earth. According to a definition by the Inter-Agency Debris Coordination Committee (IADC) “space debris are all man-made objects including fragments and elements thereof, in Earth orbit or re-entering the atmosphere, that are non-functional” [1]. According to J. C. Liou, even if we stop all the space launches the amount of space debris will remain constant up to 50 years but will increase later due to collisions among them [3], [4]. Till December 16, 2019 a total of 20047 objects are on orbit out of which 5370 objects are payloads and 14677 are debris, this means about 73% of the objects in orbit constitutes debris. [2] The rate at which the debris is generated is much greater than the rate at which this debris deaccelerates, leaves the earth orbit and re-enters the earth atmosphere. We can protect the future space missions from huge debris particles that are traceable but the small debris elements pose a major threat. In this paper we propose a technique to remove the small debris particles from Lower earth orbits based on cold welding. Cold welding is the process in which two similar metals stick to each other when there is a metal to metal contact in space. This happens because on the ground these metals have layers of oxides thus, two pure metals never come in contact but in space, due to wear and tear, this layer of oxides get removed irreversibly and as a result, pure metals come in contact and the adhesive forces cause the metals to join. The debris is orbiting around the earth at a speed of 17500 mph [10]. For our system we use a composite material made up of a combination of elements that usually orbit the earth. Since, in relative frames they are stationary by increasing the velocity with controlled amount we can control the impact during contact. We will propel this composite material with the same speed around the earth as the debris, so that in their relative frames it appears stationary. By bringing the debris particles into contact with the composite material, cold welding will take place between them and then, we will send the system to international space station where the captured debris particles are removed from the composite material. By repeating this process, we can remove most of the small debris particles of size less than 10cm which are orbiting around the earth in lower earth orbit.

Ball milling is widely used for producing powders of thermoelectric materials owing to its simplicity and scalability. In this research, we investigated the particle shape and size in p-type Bi-Sb-Te materials—the best-known and only commercially available thermoelectric materials at present—after high-energy ball milling. Although Bi-Sb-Te materials are known to be brittle, some ductile properties, such as particle agglomeration and welding, were observed. To avoid an increase in particle size via welding and to obtain particles with highly uniform sizes, two-step ball milling was performed and particle sizes were analyzed. The ball-milled powder was consolidated and sintered, and the resulting pellets showed no crystallographic orientation and consequently exhibited uniform thermal and electrical conductivities regardless of measurement direction. [ABSTRACT FROM AUTHOR]

This work focuses on the synthesize of nanostructured (Fe65Co35)100-x (Pr6O11)x (x = 0, 5) powders using high energy ball milling. The influence of Pr6O11 on structural, morphological and magnetic properties of Fe65Co35 nanoparticles were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) with a dispersive energy analyzer (EDS), vibratory sample magnetometer (VSM) and differential scanning calorimetry (DSC). Results show that the praseodymium oxide addition increased the decrement rate of the crystallite size with milling time of about 27 % and decreased the increment rate of the internal micro-strain of 50 %. Moreover, because of its high grain fragmentation tendency, Pr6O11 increases the hardness and brittleness of Fe-Co powders. Moreover, it minimized the cold welding between Fe-Co ductile particles leading to a significant decrease in the average particle size (~1µm). The magnetic measurements conducted at room temperature show that the saturation magnetisation (Ms) and the coercivity (Hc) increased with milling time in both compositions. A low Ms and high Hc values were detected in (Fe65Co35)95 (Pr6O11)5 nanoparticles. The results demonstrated a soft ferromagnetic nature in all of the synthesized nanoparticles with Ms in the range 207 - 216 emu/g and Hc is found to be 113 Oe. [ABSTRACT FROM AUTHOR]

Fe-based PM alloy powder of Fe-2.5Ni-0.5Mo-2Cu-0.4C was pressed by high velocity compaction combined with die wall lubrication, and the effect of die wall lubrication on high velocity compaction behavior and sintering properties of the Fe-based PM alloy were studied. The results indicate that the impact force, green density, sintered density of samples increase with the augment of the impact velocity and die wall lubrication. Compared with that without die wall lubrication, the green density and sintered density of the sample with die wall lubrication are about 0.07-0.12 g/cm3 and 0.08~0.11 g/cm3 higher at the same impact velocity, respectively, while the ejection force of the die wall lubricated sample is much smaller, and reduced about 26%~36%. The green compact with die wall lubrication has much fewer porosity than that without die wall lubrication, and more mechanical bonding and cold welding regions are observed. The sintered samples mainly consists of gray pearlite and white ferrite, and more pearlite is observed in the sintered sample with die wall lubrication.

The incidence of Zimmer modular revision (ZMR) hip system fractures is rare. The material of the component decreases the risk of corrosion which titanium-based modular would lower the degree of degradation despite cold welding of the component. In this case presentation, we will discuss 2 cases of implant failure from the cone taper junction of the stem and discuss the susceptible causes of the failure. The new generation of surgery products has numerous successful outcomes and has facilitated the way for modern orthopedic surgeons. Despite the high rate of satisfying results, reports of implant failure are rare. We present 2 patients in similar situations referring to the same model implant failure. It can be noticed that the force tolerance because of their weight might be a risk factor and some other factors may be missed, including providing sufficient distal bone support for the implant. [ABSTRACT FROM AUTHOR]

Magnetic pulse welding is an innovative joining method that allows combining dissimilar metals. The article discusses weldability of copper rings with steel rods in order to study the possibility of using single-turn inductor. All specimens were welded with a discharge energy of 18 kJ. Significant deformations of copper rings were observed. Metallographic examination of welds revealed no defects. High-quality joining of metals in the welding zone with a characteristic wavy boundary interface was noted. However, to obtain more information on the exact mechanisms of weld formation, it is recommended to carry out numerical modeling of the process. [ABSTRACT FROM AUTHOR]

Magnetic-pulse welding is an innovative joining method that allows combining dissimilar metals. The article discusses weldability of copper rings with steel rods in order to study the possibility of using single-turn inductor. All specimens were welded with a discharge energy of 18 kJ. Significant deformations of copper rings were observed. Metallographic examination of welds revealed no defects. High-quality joining of metals in the welding zone with a characteristic wavy boundary interface was noted. However, to obtain more information on the exact mechanisms of weld formation, it is recommended to carry out numerical modeling of the process. [ABSTRACT FROM AUTHOR]

Space Debris is a major problem posing a great threat to all the future space travels as well as to all the satellites which are orbiting around the earth. According to a definition by the Inter-Agency Debris Coordination Committee (IADC) "space debris are all man-made objects including fragments and elements thereof, in Earth orbit or re-entering the atmosphere, that are non-functional" [1]. According to J. C. Liou, even if we stop all the space launches the amount of space debris will remain constant up to 50 years but will increase later due to collisions among them [3], [4]. Till December 16, 2019 a total of 20047 objects are on orbit out of which 5370 objects are payloads and 14677 are debris, this means about 73% of the objects in orbit constitutes debris. [2] The rate at which the debris is generated is much greater than the rate at which this debris deaccelerates, leaves the earth orbit and re-enters the earth atmosphere. We can protect the future space missions from huge debris particles that are traceable but the small debris elements pose a major threat. In this paper we propose a technique to remove the small debris particles from Lower earth orbits based on cold welding. Cold welding is the process in which two similar metals stick to each other when there is a metal to metal contact in space. This happens because on the ground these metals have layers of oxides thus, two pure metals never come in contact but in space, due to wear and tear, this layer of oxides get removed irreversibly and as a result, pure metals come in contact and the adhesive forces cause the metals to join. The debris is orbiting around the earth at a speed of 17500 mph [10]. For our system we use a composite material made up of a combination of elements that usually orbit the earth. Since, in relative frames they are stationary by increasing the velocity with controlled amount we can control the impact during contact. We will propel this composite material with the same speed around the earth as the debris, so that in their relative frames it appears stationary. By bringing the debris particles into contact with the composite material, cold welding will take place between them and then, we will send the system to international space station where the captured debris particles are removed from the composite material. By repeating this process, we can remove most of the small debris particles of size less than 10cm which are orbiting around the earth in lower earth orbit. [ABSTRACT FROM AUTHOR]

Li-Sn alloys are of considerable interest in the design of plasma facing systems for nuclear fusion reactors. This letter reports the production of Li-Sn alloys by mechanical alloying, followed by cold pressing. Li atomic concentrations below 25 at.% were studied. Powder morphology during milling evolves from cold welded, rugose powders, to spherical or faceted smoother powders, and finally to thin large discs. Cold-welding and alloying are the predominant mechanisms observed up to 24 h milling. An out of equilibrium distribution of LixSny intermetallic particles with sub-micrometric size forms. Milled powders could be formed into pellets by cold pressing due to its ductility and cold welding behaviour. Contamination free Li-Sn alloys, with 5, 15 and 25 at.% Li, were successfully produced by this method. The main phases identified are β-Sn, Li2Sn5 and LiSn. Phase composition evolves with annealing, with LiSn decrease and Li2Sn5 increase.

The microstructure and mechanical properties of ZL114A alloy after cold welding were studied by using SEM, EDS, OM, Vickers hardness and WDW-100KN universal tensile tester, the temperature field distribution was calculated by the SYSWELD FEM simulation. The results show that the largest molten pool and peak temperature are 6mm and about 512℃, which are obtained in the 20V and 24A process parameters. The average tensile strength, yield strength, elongation and HV hardness at T6 state are 334,276MPa,7.4% and 68HV, which are changed to 156,108MPa, 12.8% and 60HV after the cold welding process of the ZL114A alloy, leading to a decline of strength by 53.3% and 60.9%, together with an increase of elongation by 72.9%. The same mechanical properties are attained in the cold welding of ZL205A alloy and the normal processing 4mm round hole, the average tensile strength, yield strength and elongation are 232,218MPa and 3.8%. The primary and binary eutectic Si phases are shown as a spherical morphology at T6 state, dimple fracture is the main fracture mechanism, accompanying with numbers of intergranular fracture. The material organization is changed from the T6 state into the solid solution state after the cold welding process, the silicon particles that distributed nearby the grain boundaries are gathered together and the Mg and Si elements are distributed in the grain boundary area coincidentally, the Cu,V and Mn elements are dissolved into the primary Al matrix, some Al2Cu phases are precipitated along the grain boundary.

The paper describes an advanced discrete-element based mechanical model, which allows modelling contact interaction of ductile materials with taking into account fracture and surface adhesion by the cold welding mechanism. The model describes these competitive processes from a unified standpoint and uses plastic work of deformation as a criterion of both local fracture and chemical bonding of surfaces in contact spots. Using this model, we carried out a preliminary study of the formation of wear particles and wedges during the friction of rough metal surfaces and the influence of the type of forming third body (interfacial) elements on the dynamics of the friction coefficient. The qualitative difference of friction dynamics in the areas of the contact zone characterized by different degrees of mechanical confinement is shown. [ABSTRACT FROM AUTHOR]

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To simulate the agglomeration of nanoparticles subjected to an external electric field, we develop a method to calculate the induced charge density in surface atoms to account for the inter-particle attractions between metallic nanoparticles, based on classical electrodynamics. A polarizable particle is subjected to dielectrophoresis force in a non uniform AC electric field. The induced charge density in a surface atom layer is redistributed to minimize the electric field inside the particle, restricting the total charge density of nanoparticles during the molecular dynamics simulations via a Lagrange multiplier method. The developed method is implemented in the LAMMPS code, where Lorentz and Coulomb forces applying on partially charged surface atoms are embedded to correct atomic motions in response to the applied AC electric field. In numerical examples, the electric field around a spherical nanoparticle shows good agreement with the analytical solution under external electric field. The proposed method is turned out to be more efficient for the problems of large particles since the ratio of surface to bulk atoms decreases as the size of particle increases. When an external electric field isexerted, the ordered aggregation of gold nanoparticles is observed in physical experiments and investigated through the LAMMPS simulations. The developed method successfully simulates that the nanoparticles are not only aligned in the direction of electric field but also formed lattice bonds due to the charges induced by the electric field. [ABSTRACT FROM AUTHOR]

In the work the current state is analyzed and the relevance of investigations of the process of magnetic pulse welding of flat parts from similar and dissimilar metals is confirmed. The results of investigations of possibility of realization of magnetic pulse welding of flat specimens on the modified serial installation N-126A by means of experimental pancake rectangular inductor are given. The scheme of the process is given. The technology of producing joints of flat metal parts with a thickness of 1.0...1.5 mm from similar materials from aluminum A5N and AMg2 alloys, as well as from dissimilar - copper, A5N and AMG2 alloy with stainless steel 12Kh18N10T (hardened) is described. The carried out metallographic examinations showed that common for magnetic pulse welding of similar and dissimilar metals is a specific joining of welding plates in the areas equidistant from the center of the flat coil of the inductor. The thickness of the moving plates decreases, and the microhardness in the welding zones increases. The quality welding was fixed within the two-zone shape of joining. The quality of the welded joint was evaluated by the results of mechanical strength tests. [ABSTRACT FROM AUTHOR]

A jammed screw is a well-known complication of locking plates. Noncompliance to the standard techniques, nonusage of torque limiting screwdrivers and manufacturer-specific instrumentations are the common causes of jammed locking screw heads. Previously, various techniques have been described for the retrieval of jammed locking screws by damaging the screw head, using conical reverse threaded drill bits and often cutting off the plates at jammed screw sites that often generate metal debris and cause bone and soft tissue damage of unknown extent. We present a simple technique and a novel device that does not damage the screw head or the plate, and therefore, no metal debris is generated. The threads on the terminal part of the screw are used to disengage the jammed locking screw head from its locking hole. [ABSTRACT FROM AUTHOR]

The paper provides analysis of the state-of-the-art and confirmation of the relevance of studying the process of magnetic- pulse welding (MPW) of flat parts from similar and dissimilar metals. Results are presented of studying the possibility of performance of magnetic-pulse welding of flat samples in a modified batch-produced N-126A unit, using an experimental flat rectangular inductor. Process scheme is given. Technology is described for producing joints of flat metal parts 1.0-1.5 mm thick of similar materials of A5N and AMG2 alloys, as well as dissimilar materials - copper, A5N alloy and ANG2 alloy to 12Kh18N10T stainless steel (cold-worked). Conducted metallographic studies showed that a common feature for MPW of similar and dissimilar metals is specific bonding of welded plates in the zones (regions) equidistant from the center of the inductor flat turn. Thickness of mobile plates becomes smaller, and microhardness in the welding zones becomes higher. Sound welding was found within the two-zone joint shape. Welded joint quality was assessed by the results of mechanical strength testing. [ABSTRACT FROM AUTHOR]

The combination of a top-down and a bottom-up fabrication approach will be a key technology to overcome the minimum size limit of the top-down approach. Gentle cold welding is a promising method to connect nano objects without appreciable damages to the nano device in a bottom-up approach. We developed the gentle cold welding method using the combination of an electrical field and an atomic rearrangement. The formulated process was visualized between gold tips using a transmission electron microscope. The initial connection mechanism was divided into three modes depending on a bias voltage between tips; (1) physical contact, (2) atom extraction, and (3) field evaporation, depending on the electrical fields. All the nano connections grew by the atomic rearrangement driven by gold surface self-diffusion. The grown connections were single crystalline structures. These results suggested that this welding will be a useful method to build up future nano devices and systems. [ABSTRACT FROM AUTHOR]

Cold welding refers to an effect related to space (vacuum). The heavy vibrations during a launch subject interfaces (hold down points) to oscillating motions which may lead to formation of a kind of “friction weld”. If so, these mechanisms may get stuck, and deployment will be hindered. This may endanger the functionality of the mission (instruments) or even the whole spacecraft (if solar panels do not open). Several studies have been done to characterize material combinations (including coatings) for their ability to cold welding in space. Meanwhile, also during launch grease free contacts are demanded. If grease hat to be omitted, the risk of cold welding under fretting was found to increase (when testing in high vacuum). To rate this risk under launch conditions, the test method was recently extended for testing under launch conditions. The new tests procedure consists of fretting applied in the sequence in air, low vacuum and high vacuum. The paper shall present first results gained with this new method of testing in launch conditions and compare them to previous studies done in vacuum. Following the need of space industry on mechanisms for launch and in-orbit life, a first set of combinations of materials and coatings were selected for this new test sequence where fretting is now applied in a sequence of air, low vacuum and high vacuum. Under this sequence, the measured levels of adhesion and it’s evolvement was found to differ strongly from tests done formerly. The paper outlines these first results and compares them to existing data.

Tensile and creep properties of dissimilar cold weld joints (Al (metal)–Cu50Zr50 (metallic glass)) are investigated using molecular dynamics simulations. Embedded atom method potential is used to model the interactions between Al–Cu–Zr atoms. Cold welding is carried out at three different velocities (20, 30 and 40 m/s) and for three interferences (0.4, 1.3 and 2.3 nm). The strength of the welded joints is measured using the tensile test carried out at a strain rate of 1.5 × 109/s. Structure studies by radial distribution function analysis indicate amorphisation of Al in the weld regions. Tensile studies show that the maximum strength is obtained in the sample that is welded for 1.3 nm interference. Creep studies carried out over range of stresses (200–350 MPa) and temperatures (200–500 K) show very short primary creep and significant steady-state creep. The stress exponent n has two values; at lower stress, n = 1.2, and at higher stress, n = 4.06, respectively. The deformation mechanisms are observed to be slip by Shockley partial dislocation and by twinning in Al region. The icosahedral cluster population in metallic glass decreases as the temperature increases and contributes to large plastic strain. [ABSTRACT FROM AUTHOR]

The microscopic surface films existing on the top of metallic layers play an important role in the process of joining by plastic deformation. The bond formation during cold welding processes is basically associated with the fracturing of surface films to produce intimate metallic contacts. The present paper aims at providing a numerical model to describe the cracking pattern of brittle surface films bonded to the ductile substrates. A microscale finite element model is developed which takes into account the fracturing mechanisms of thin surface films in roll bonding processes. The presented model is calibrated by using the existing experimental data for an aluminum alloy covered by a thin layer of oxide film. The model is also validated against a well‐known analytical model for periodic cracking. The distribution of stresses within the fractured surface film demonstrates that the generated cracks in the surface film have essentially a periodic pattern. Moreover, it is shown that the crack spacing is highly dependent on the properties of the surface film. Finally, the obtained results for the roll bonding show that a crack density saturation takes place at the entry of the roll bite where a small surface expansion is applied to the rolled samples. [ABSTRACT FROM AUTHOR]

The basic problems that arise in the course of repairing the welded joints of high-temperature elements of heat-recovery boilers, manifolds, and steam pipelines of steam-gas power plants produced from heat-resistant T91/P91 chromium steels while in use are set forth. A review and analysis of repair technologies used abroad is presented. [ABSTRACT FROM AUTHOR]

The advent of locking plates has brought new problems in implant removal. Difficulties include cold welding between the screw head and locking screw hole, stripping of the recess of the screw head for the screwdriver, and cross-threading between threads in the screw head and screw hole. We are describing a technique which allowed us to remove such cold-welded, jammed single screw with simple instruments at hand and complete the prescribed operation smoothly. A 32-year-old female patient reported to us with a broken clavicle locking plate, who was operated 3 years back for fracture clavicle right side. The patient had complaints of pain and deformity in the right clavicle region for 3 months following lifting heavy weight. X-ray showed broken implant with nonunion of clavicle. The patient was planned for implant removal, freshening of edges, and fixation with anatomical clavicle plate with bone grafting. All the screws were removed with standard screw driver when it was found that the second screw of medial broken plate was jammed, round headed, and cold welded. We bent both ends of broken medial plate around screw and removed screw by just rotating bent plate anticlockwise. Fracture ends were freshened and fixation was done with anatomical clavicle locking plate and bone grafting. The patient did not develop any postoperative complication. This technique is very quick, easy to perform, and inexpensive without the use of plate cutting blade, burr, hollow mill, and other instrumentation. This technique can be used in peripheral hospitals in India where advanced gadgetries may not be available. There is no problem of thermal necrosis to the bone or the surrounding soft tissue. Osteoporotic bone is a limitation of the above method as the bone may break while bending the plate and is possible only with a single locking screw.

The technology of welding dissimilar metals at the nanoscale is of importance in the fabrication of electronics. In this work, we achieved cold welding of aluminum (Al) and copper (Cu) nanowires by simple mechanical contact without extra heating and/or voltage applied in transmission electron microscopy (TEM). During the welding process, the welding surface gradually disappeared due to the significant inter-diffusion between Al and Cu under a relatively low pressure, which resulted in the formation of an Al/Cu solid solution and Al3Cu2 intermetallic compound. The following in-situ TEM tensile test revealed that the joint displayed super plasticity with a total elongation even beyond 100%. The corresponding plastic deformation was dominated by the partial dislocation glide and grain rotation. Our results not only shed light on developing the advanced welding technology for dissimilar metals at the nanoscale but also improved the understanding of the joint deformation mechanisms. [ABSTRACT FROM AUTHOR]

Abstract A low oxygen induction thermal plasma (LO-ITP) system was developed and a cold-welding behavior of bare fine metallic aluminum powders prepared by the system developed here was observed. This behavior is suitable for a metal precursor for metal matrix composites (MMC) since fine and bare metal particles may contribute to obtaining a well-dispersed state and a high relative density respectively, which lead to the enhancement of the reinforcement of MMC properties. The electric conductivity of the aluminum green pellet compacted at 200 MPa reached 2.9 × 107 S/m, which is comparable to that of bulk aluminum, indicating that the cold welding was taken place since the surface contamination layer such as an oxide may be negligibly thin. Therefore, the powder obtained in this work is expected to be useful in enhancing the reinforcement of MMC properties. Graphical abstract Image 1 Highlights • A new low oxygen induction thermal plasma system was developed. • Bare fine metallic Al powders were successfully prepared. • The electric conductivity of the Al green pellet reached that of bulk Al. • This system can be used as a production process for fine bare metal powders. [ABSTRACT FROM AUTHOR]

Mechanical plating deposits coatings by cold welding fine particles to a workpiece through ball or shot impact treatment, for example in ball mills. This process offers flexibility in selecting material systems because the formation of coatings occurs in the solid state at near room temperature and ambient pressure. However, parametric optimization of the process remains a challenge since many parameters affect the process efficiency. The goal of this study was to numerically investigate the behavior of the balls and a substrate sample in a planetary ball mill and thus to elucidate the mechanisms involved in this mechanical plating treatment. An aluminum substrate with aluminum‑carbon nanotube coating system that was previously investigated experimentally was simulated. A discrete element method model was proposed to perform numerical simulations to predict the energy, frequency, and angle of ball-to-substrate collisions. Measurements were also conducted to determine the friction coefficient necessary for the simulation. The results revealed that small balls caused more frequent and mild collisions with the substrate predominantly in the tangential direction. These collisions are assumed to be the primary contributor to the coating formation. Collisions between large balls and the substrate were less frequent but had greater intensity, and the probability of tangential and normal collisions was approximately equal. The numerical results were qualitatively supported by the as-treated substrate roughness measurements determined in this study. [ABSTRACT FROM AUTHOR]

High damping capacity and low density M2052/Al composites were successfully fabricated using the accumulative roll bonding (ARB) method, by taking advantages of high damping capacity for M2052 alloy (Mn-20Cu-5Ni-2Fe, at%) particles and excellent mechanical properties and low density for Al matrix. The 15 wt% M2052 particles were uniformly dispersed in Al-matrix after 10 ARB process cycles. M2052/Al composites have a low density of 2.9 g/cm 3 , which is just a little higher than that of Al. After ARB process and a subsequent hydrogen annealing, the M2052/Al composites exhibit both high room temperature damping capacity and good mechanical properties: the highest damping capacity is 0.01 at 270 K, 5 times that of pure Al at the comparative temperature; the ultimate tensile strength is about 70 MPa (about 35% higher than that of pure Al), and the total elongation reaches 24%. The simultaneous enhancements on damping capacity and tensile strength of the M2052/Al composites can be attributed to the high damping capacity and the dispersion strengthening of M2052 phase, as well as the good bonding between the M2052 particles and Al matrix resulted from the ARB technique. [ABSTRACT FROM AUTHOR]

Mechanical bearings in a flywheel energy storage system (FESS) may experience unique wear patterns due to the vacuum condition that such systems operate under. The FESS discussed herein uses an aluminum flywheel rotor hub with an integrated shaft and full silicon nitride ceramic bearings. The bearings experienced fretting wear, as is common to many bearing-shaft systems, which eroded the naturally forming oxide layer on the surface of the shaft which was not replaced due to the lack of oxygen. This exposed the soft aluminum surface below creating the opportunity for material transfer between the surfaces and cold welding between components to occur. The existence of fretting and material transfer is demonstrated, and the opportunity for cold welding between components is discussed. The effects of these processes on system components are described. Recommendations to avoid or mitigate fretting and adhesion damage to the system are made for the studied FESS in particular, and, more generally, similar systems operating in vacuum conditions. [ABSTRACT FROM AUTHOR]

A phase field model is developed to predict curved dendrite growth in the gas tungsten arc (GTA) welding pool of an Al-Cu alloy. The equations of temperature gradient, pulling velocity and dendrite growth orientation are proposed to consider the transient solidification process during welding. Solidification microstructures and solute diffusion along the fusion boundary in the welding pool are predicted by using the phase field model coupled with transient solidification conditions. Predicted primary dendrites are curved and point toward the welding direction. Welding experiments are carried out to observe solidification microstructures of the weld. Comparisons of simulation results with experimental measurements are conducted. Predicted dendritic morphology, dendrite growth orientation, primary dendrite arm spacing and initial cell spacing give a good agreement with experimental measurements. [ABSTRACT FROM AUTHOR]