Diamond has high hardness and good wear resistance. It is widely used in cutting tools and workpieces. Brazing is an effective method to realize high quality cemented carbide joints in various materials connection technologies. This paper analyzes the research status of diamond brazing in detail. The materials used as brazing filler in diamond brazing are reviewed. Copper base filler and nickel base filler are the most commonly used brazing filler in diamond brazing. The advantages and disadvantages of diamond grinding tools under different production methods are analyzed. In addition, a series of new brazing alloys such as amorphous Ni based brazing filler metals are analyzed. Finally, the development trend of diamond brazing is pointed out.

Down to the road of miniaturization and high power density, the heat dissipation is becoming one of the critical factors restricting further development of advanced microelectronic devices. Traditional polymer-based thermal interface materials (TIMs) are not competitive for the high efficiency thermal management, mainly due to their low intrinsic thermal conductivity and high interface thermal resistance. Solder-based TIM is one of the best candidates for the next generation of thermal interface materials. This paper conducts a perspective review of the state of the art of solder TIM, including low melting alloy solder TIM, composite solder TIM and nanostructured solder TIM. The microstructure, process parameters, thermal performance and reliability of different TIMs are summarized and analyzed. The future trends of advanced TIMs are discussed.

Due to local uneven heating during the welding process, the residual stress of the structure after welding affects the reliability of it. In order to ensure the reliability, it is of great significance to test the residual stress distribution of the welded joint. It has always been the focus to find a simple and feasible method for residual stress testing to quickly and accurately obtain the residual stress distribution of welded joints. The mechanical measurement method has high measurement accuracy, convenient and easy operation, but it will cause certain damage to the components. Physical measurement method can avoid damage to components, but its test cost is usually high, and its measurement accuracy can also be affected by the material microstructure characteristics of welded components. Based on the advantages and disadvantages of these two residual stress test methods, a modal test method is proposed. This method is a non-destructive measurement method. Based on the mathematical relationship between the residual stress of the welded structure and the natural frequency (mathematical model), the natural frequency is measured through the modal test to calculate the residual stress quickly. However, it is difficult to establish a mathematical model with this method, and it is not suitable for realization.

This study has been conducted to evaluate the application of silver nanoparticles (NPs) in Electrically Conductive Adhesives (ECAs), filled with hybrid silver flakes and NPs, and silver flakes as a control sample, at a filler loading of 78 wt.%, 83 wt.% and 88 wt.% and cured at 150 ℃ and 180 ℃, respectively. The results show that the electrical and thermal conductivities of ECAs were improved with the increasing of filler loading and curing temperature. Adding silver NPs in silver flakes negatively affected the electrical and thermal conductivities of ECAs at a low filler mass fraction of 78 wt.%, because the segregation of NPs enlarged the average distance of silver flakes; while it positively influenced the electrical and thermal conductivities of ECAs at a loading ratio of 88 wt.%, probably due to NPs filling in the gaps between silver flakes or even sintering together with each other or with silver flakes, especially when curing at high temperature of 180 ℃.

In order to solve the problem of automatic defect detection and process control in the welding and arc additive process, the paper monitors the current, voltage, audio, and other data during the welding process and extracts the minimum value, standard deviation, deviation from the voltage and current data. It extracts spectral features such as root mean square, spectral centroid, and zero-crossing rate from audio data, fuses the features extracted from multiple sensor signals, and establishes multiple machine learning supervised and unsupervised models. They are used to detect abnormalities in the welding process. The experimental results show that the established multiple machine learning models have high accuracy, among which the supervised learning model, the balanced accuracy of Ada boost is 0.957, and the unsupervised learning model Isolation Forest has a balanced accuracy of 0.909.

Friction stir welding (FSW), as a growing welding technology, from its genesis in 1991, was attended by many researchers in interdisciplinary fields of science and engineering. The current paper presents a bibliometric analysis of the subject and can be addressed as guidance for the researchers who want to explore this field of welding technology. The research growth of FSW, most productive and influential authors, disciplines, leader journals, countries, and institutions are investigated. The highly influential papers in two historical periods and top keywords are also introduced. This paper summarizes the growth structure of FSW during the last 26 years and provides concise bibliometry.

Ceramic-copper substrate is used to achieve the combination between copper and ceramic (Al₂O₃ or AlN) under high temperatures by bonding or brazing process, then through dedicate lamination – etching technology to develop the designed layout in copper surface, finally parts go with plating and singulation process for surface treatment before shipping to the end-user. Ceramic-copper substrate has perfect performance in terms of insulation, thermal conductivity, solderability, and adhesion strength. Besides, the copper on surface can afford huge current due to the fact that ceramic has good reliability and thermal-cycling performance. According to technical visit and audit to suppliers’ manufacturing process and based on several years’ experience of mass production for electric vehicle power module package, this article introduces two mainstream ceramic-copper substrate processing methods currently on the market: direct bond copper (DBC) and active metal brazing (AMB) which can be widely used for the intelligent power module and electric vehicle power module, also introduces the major failure mode during application and analyzes the root cause for each failure mode, clarifies key incoming monitoring method, like crosshatch, silver plating thickness measurement and blister test. This article also clarifies the Incoming Quality Control system, which can provide guidance to process engineer during the application.

Equiatomic CrMnFeCoNi high entropy alloy prepared by powder metallurgy was remelted by laser. The relative density and microstructure of fusion zone are evaluated. The nanoindentation tests are conducted to reveal the hardness difference of dendrite arms and interdendritic areas. Tensile tests are conducted to assess the mechanical properties of remelted HEA. After laser remelting, the number and morphology of voids changed significantly. Dendritic structure with face-centered cubic phase form in the fusion zone. Fe, Cr and Co are enriched in dendrite arm, while Mn and Ni are enriched in interdendritic area. Elements segregation led to a nanohardness difference between dendrite arm and interdendritic area. Local deformation occurs in interdendritic area during tensile tests and results in a fracture with directionality.

Friction element welding technology is rich of flow drill screws combined with friction welding technology and is developed for the hot-forming steel plate and aluminum alloy welding of car body-in-white. In this paper, the principle of RES welding technology, equipment, technical characteristics, application condition and welding parameters are analyzed systematically. Moreover, the changing laws of welding parameters and welded joint quality control standards are described, which provides the necessary technical support for safety and light-weight car body design requirements. This study has high practical application value, and enriches the automobile body joining technology.

Owing to diamond excellent physical and chemical properties, so synthetic diamond abrasives are extensively used in manufacturing diamond tools are utilized in machining hard and brittle materials. The brazing technology is exploited with strong bonding force between the diamond and substrate, which can realize metallurgical and chemical bonding between the filler metals and diamond abrasives. In this paper, the research reports on nickel-based fillers for brazing diamond grains at home and abroad in recent years are reviewed systematically, with emphasis on the influence of alloying elements and active elements on the properties of nickel-based fillers. The advantages and disadvantages of Cr, B, Si, P, Mn, Fe, Cu, W, C in nickel-based fillers and the negative effects of impurity elements were summarized. The shortcomings in the research and application of nickel-based fillers were pointed out, which provided theoretical guidance for further systematic research and development of related technologies.

T-joint titanium alloy structures are commonly used in aircraft manufacturing, and their laser welding process is relatively mature, but due to the strict requirements of the airplane production, the angular deformation caused by uneven heat input across the sheet is still not negligible, so active control needs to be imposed. In this paper, an active deformation control method based on programmable multi-point flexible support is proposed and validated. In response to the problem that the traditional rigid clamping and pre-stressing are not adapted to the T-structure thin sheet, this study has designed a multi-point flexible support with microcontroller and electric actuators, which can monitor the stress state of the current support position in real time during the welding process and make dynamic adjustment,so that the weld deformation could be effectively reduced in this way.

Cu-Sn-Ti brazing filler is a new type of copper-based brazing filler for brazing diamond tools currently used in industry, but it suffers from poor wear resistance, high brazing temperature and low bond strength. This paper provides a way to improve the strength of diamond-brazed joints by adding zirconium carbide and tungsten carbide reinforcing phase particles to the Cu-Sn-Ti alloy, respectively. Diamond particles were attached to Q460 steel using Cu-Sn-Ti composite filler with the addition of the reinforcing phase, and experimental instruments such as scanning electron microscope, X-ray diffractometer and energy spectrometer were used to investigate the brazed joint performance of the composite brazing material for brazing diamond. The results show that the addition of enhanced phase particles resulted in a metallurgical reaction at the joint of the composite brazed diamond, achieving a higher strength joint with no obvious cracks at the interface, while the addition of 15 wt.% WC resulted in excellent wear resistance and the highest hardness at the joint interface.

The submerged arc brazing method was used to connect the tin-based babbit alloy with the steel matrix. The microstructure of the submerged arc brazed Babbitt interface layer on the surface of Q235B steel was analyzed by OM, SEM and EDS and the hardness properties of the joint interface layer were tested by MH-5 microhardness tester. the result of research shows that a layer of canine-shaped intermetallic compound with uneven thickness is formed at the interface, and the thickness is 10 – 20 μm. The interface layer includes two kinds of compound layers, namely the FeSn layer near the side of the steel substrate and FeSn₂ layer near the side of the babbit. During the interfacial reaction process, Fe atoms in the steel matrix dissolve into the liquid babbit alloy and form a certain concentration gradient at the interface. The farther from the interface, the lower the Fe atom concentration. The growth of Gibbs free energy of FeSn is lower when the temperature is above 780.15 K, and the temperature during the welding process is much higher than 780.15 K, moreover the precipitation temperature of FeSn is higher. Therefore, in the subsequent cooling process, FeSn is first precipitated from the interface near the side of steel matrix and then FeSn₂ is precipitated from the interface near the side of babbit alloy. Microhardness test showed that the intermetallic compound at the interface layer significantly improved the hardness properties.

Active soldering of 5A06 Al alloy was performed at 300 °C by using Sn-1Ti and Sn-1Ti-0.3Ga active solders, respectively. The effects of soldering time on the microstructure and mechanical properties of the joints were investigated. The results showed that the Sn-1Ti solder broke the oxide film on the surface of the Al substrate and induced intergranular diffusion in the Al substrate. When Ga was added to the solder, severe dissolution pits appeared in the Al substrate due to the action of Sn-1Ti-0.3Ga solder, and many Al particles were flaked from the matrix into the solder seam. Under thermal stress and the Ti adsorption effect, the oxide film cracked. With increasing soldering time, the shear strength of 5A06 Al alloy joints soldered with Sn-1Ti and Sn-1Ti-0.3Ga active solders increased. When soldered for 90 min, the joint soldered with Sn-1Ti-0.3Ga solder had a higher shear strength of 22.12 MPa when compared to Sn-1Ti solder.

Since programing complex and dynamic heat source model for welding simulation is a complex job, the parametric methods are studied in this paper. Firstly, an overall flow to achieve automatically modeling welding was introduced. Secondly, an expert module rule for selecting welding heat source model was founded, which is based on simulation knowledge and experiences. Thirdly, a modularity routine method was investigated using writing with C++ programing, which automatically creates subroutines of 3D dynamic heat source model for user. To realize the dynamic weld path, the local weld path coordinate system was moved in the global coordinate system and it is used to model the direction of weld gun, welding path and welding pose. The weld path data file was prepared by the automatic tool for the welding heat source subroutines. All above functions were integrated in the user interface and the connection with architecture was introduced. At last, a laser beam welding heat source modeling was automatically modeled and the weld pool geometry was compared with the reported literature. It demonstrated that the automated tool is valid for welding simulation. Since modeling became convenient for welding simulation using the tool proposed, it could be easy and useful for welding engineers to acquire the needed information.

In this paper, the phenomena of Mg₂Sn-induced Sn whisker growth were explored on the surfaces of Mg/Sn/Mg ultrasonic-assisted soldering joints after aging treatment. The in-situ observation and thermal analysis confirmed that the formation and the corrosion of Mg₂Sn nanoparticles were the dominant reason of Sn whisker growth. The Mg₂Sn accumulation at the grain boundaries would pin the dislocation slip and affect the continuity of whisker growth, and the boundary angle would thus play a decisive role in the growth shape of Sn whiskers due to the pining effect of Mg₂Sn. This study might be conducive to elucidating the growth behavior of Sn whiskers and provide the exploration strategy to further improve the bonding strength of Mg/Sn/Mg ultrasonic-assisted soldering joints.

The precipitated phases in the WNZ, TMAZ, HAZ and BM of the friction stir welding (FSW) joint were observed using the transmission electron microscopy (TEM) and the lattice fringe spacing of the precipitated phases was measured. Combined with X-ray diffraction (XRD), the types of precipitated phases among the joint were confirmed and then the strength mismatch mechanism was revealed. The results show the precipitated phases of 7075 aluminum alloy FSW joint mainly consist of MgZn₂, AlCuMg and Al₂CuMg. The micro-zone of the joint experienced different thermal cycles, the types and sizes of precipitated phases are different and the strengthening effect is different. The strengthening effect of the AlCuMg and Al₂CuMg are better than that of MgZn₂. The precipitated phase in the WNZ mainly includes AlCuMg and Al₂CuMg, as well as the grain size is fine, the microhardness in this zone is pretty high. The number of precipitated phase AlCuMg and Al₂CuMg is smaller in the TMAZ and the MgZn₂ is relatively more, which lead the microhardness decrease. The number of precipitated phase MgZn₂ is relative larger in the HAZ, as well as the grain coarsening, the microhardness in this zone is lowest of the joint. At the same time, there are the precipitate free zones (PFZ) among the 7075 aluminum alloy FSW joint, which decreases the micro-hardness of the whole joint to some extent.

A two-dimensional model was established for the first time by coupling moving wire and arc in CMT-WAAM and GMAW-WAAM process, revealing the temperature, potential and droplet transition behavior of droplet metal. The droplet transition and the change of droplet transfer mode under different wire feeding speed were analyzed. The experiments and numerical simulation research found that droplet transition mode is projected transfer in GMAW-WAAM process under 150 A current, with a complete transition period is 14 ms. The droplet transition shows a short-circuit transition mode in CMT-WAAM process, with wire feeding speed of 5.5 m/min and a complete transition period is 20 ms. The droplet transition shows a mixture of droplet transfer and short-circuit transition mode in CMT-WAAM process, with wire feeding speed of 5.5 m/min and a complete transition period is 23 ms. Based on the theoretical research and experimental studies, the mechanism of droplet transfer mode in WAAM was studied, which can provide reference for optimizing parameters.

The excellent properties of SiC bring new challenges for the device packaging. In this study, the bonding strength, fracture behaviors and microstructural evolution of micron-porous Ag joint were elevated during thermal cycling (–50 oC–250 oC) in SiC/DBC (direct bonding copper) die attachment structure for different time. During harsh thermal shock test, the strength of sintered joint deceased gradually with the increase of cycling number, and the value just was half of the value of as-sintered after 1000 cycles. Coarsening of Ag grains was observed in micron-porous joint with the structure inhomogeneity and defects increasing, which were the reasons of the strength decease. In addition, it was also found that the fracture behavior of sintered joints was changed from ductile deformation of Ag grain to brittle fracture of crack propagation after 1000 cycles. This study will add the understanding in the mechanical properties of Ag sinter joining and its applications at high temperature.

The static and fatigue properties of 7B04 aluminum alloy structures connected by riveting and refill friction stir spot welding (refill FSSW) were compared and analyzed. Results show that the static compression load of the typical structure connected by riveting and refill FSSW fluctuated in the range of 117–124 kN, and the shear load was in the range of 89–95 kN. Welds spacing had a small influence on the static load of the structures joined by refill FSSW. However, the fatigue life of riveted structures was lower than that joined by refill FSSW. For the welded structure, the heterogeneous microstructures of the welded joint led to the uneven microhardness, and the hook at the lap interface bent upwards at the same time. These factors made the welded structures during the fatigue test failure along the path of sleeve moving.

Aluminium matrix composites with 70% volume fractions of SiC particles, as the reinforcements, were brazed in the vacuum furnace using Al-Si-Ti-Cu-In alloy as filler metal. The microstructure and constituent of the joints were examined by means of SEM and EDS. Meanwhile, welded joints were submitted to shear test. The result shows that high quality joints were acquired, which mainly contains honeycomb Al base phase, Ti, In rich phase and annular Si rich phase. The brazing process sincludes five stages: (1) particles cohere; (2) liquid flows and particles rearrange; (3) the sintering neck grows; (4) second liquid flows and pores fill; (5) closed pores englobe and narrow. The reducing of the sintering body’s and pores’ free surface energy drove the sintering process to continue. The maximum shear strength was 90 MPa. The fracture belongs to mixing fracture with the characteristic of both the cleavage fracture and the micro void accumulation fracture.

Variable polarity plasma arc-gas metal arc welding (VPPA-GMAW) integrates the advantages of VPPA and GMAW, and it is particularly applied to weld thick-plates aluminum alloys. High-speed camera and data acquisition system were used to analyze the arc shape and the welding process electrical signal. According to the analysis of arc swing amplitude and the approximate entropy of arc voltage signal denoised by wavelet threshold method, the influence of VPPA frequency on the arc stability was studied. The results show that the approximate entropy of GMAW arc voltage decreases with the increase of VPPA frequency in a certain range, and the stability of the hybrid arc is significantly improved. The spectral analysis shows that the arc stability is reduced due to the resonance effect between the VPPA and the GMAW arc when the VPPA frequency closes to the GMAW arc pulse frequency. The results are helpful to understand hybrid welding mechanism and the selection of welding process parameters.

A certain amount of Ti was added to the plasma cladding Fe-Cr-C coating in the early stage in order to improve the quality and properties of the coating. Ti-Fe-Cr-C composite powder was prepared by precursor carbonization-composition process. In situ synthesized TiC-Fe-Cr coatings were fabricated on substrate of Q235 steel by plasma cladding process with the composite powder. Microstructures of the coatings with different process parameters, including cladding current, cladding speed, number of overlapping cladding layers, were analyzed by scanning electron microscope. The results show that the structure of the TiC-Fe-Cr coating is greatly affected by the cladding current, the cladding speed and the overlapping cladding process. In this test, when the cladding current of 300 A and the cladding process parameter of the cladding speed of 50 mm/min are clad with three layers, a well-formed and well-structured TiC-Fe-Cr coating can be obtained in this test. TiC-Fe-Cr coating has good wear resistance and good load characteristics under dry sliding wear test conditions.

Problems such as poor structural integrity, inhomogeneous dispersion, and agglomeration of graphene in the brazing seam are typically encountered for graphene additives in a brazed joint interface. To resolve these problems, a plasma-enhanced chemical vapor deposition process was employed for in-situ preparation of a high-quality graphene-coated copper (Cu) foam composite interlayer prior to be applied for brazing carbon/carbon composite and niobium. The prepared graphene and the brazed joints were characterized via Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The results revealed that graphene was evenly distributed in the brazing seam with the help of the Cu foam, which was characterized by interconnected porosity. Simultaneously, the excellent chemical inertia of graphene inhibited the collapse of the Cu foam, based on which the thermal residual stress in the joint was effectively mitigated due to the synergistic reinforcement effect of the Cu foam (with good plastic deformation capacity) and graphene (with extremely low coefficient of linear expansion). This effect led to significant improvement in the average shear strength of the joint.

Wire arc additive manufacture (WAAM) is a new technique to fabricate large-scale complex aluminum alloy components. However, the performance of the parts is critically influenced by residual stresses and deformation. A sequentially thermal-mechanical coupled model of residual stress and deformation for aluminum alloy WAAM parts was established based on commercial FE software ABAQUS. The temperature field was calculated by the moving heat source (MHS) method. The temperature function was obtained according to the distribution of the peak temperature. Furthermore, the MHS method and segmented temperature function (STF) method were used to calculate the residual stress and deformation. The results show that the STF method satisfies both the efficiency and accuracy requirements. 1-segment, 3-segment, and 5-segment STF methods can shorten the time for mechanical analysis by 91%, 79%, 63%, respectively. The error of the residual stress and deformation are all less than 20%. STF method provides an effective way to predict the residual stress and deformation of large-scale WAAM parts.

By method of TIG, two kinds of welding materials were filled in and under certain welding craft conditions, 1Cr18Ni9Ti and 2Cr13 were welded. The microstructure of two kinds of welded joints were observed and analyzed by OM, SEM. Through seawater immersion test, polarization curves and AC impedance spectroscopy of two kinds of welding joints were obtained. The results show that 2Cr13 and 1Cr18Ni9Ti welded joints are typical columnar crystal, the microstructure is lath martensite + austenite + carbide. The welded joints that filled in 308 and H1Cr21Ni10Mn7Mo welding wires, corrosion resistance has same change rule: Austenite base metal>HAZ near Austenite>welded joint>HAZ near Martensite>Martensite base metal. The every zone contrast of two kinds of welded joint corrosion resistance obtains: the welded joints filled in 308> the welded joints filled in H1Cr21Ni10Mn7Mo.

At present, conventional flame correction has shortcomings such as random heating route and low efficiency. The welding seam of the aluminum alloy ship frame skin structure is concentrated and the frame restraint is large. It is difficult to control and eliminate the local convex deformation after welding. In order to improve the conventional orthopedic technology and improve the orthopedic efficiency, the pre-elastic deformation technology is proposed. Using the method of combining numerical simulation and experiment, the orthopedic effect of conventional and pre-elastic orthopedic technology is studied, and the influence of pre-deformation variables and heating path on deformation control of the frame skin structure after welding is simulated. The simulation results show that the technical key to the control of convex deformation lies in the control of the pre-elastic deformation and the setting of the heating route. The experimental verification results show that the pre-elastic deformation technology has a better control effect than conventional orthopedics, can significantly improve the orthopedic efficiency, and provides a new method for deformation control in the shipbuilding industry.

3 mm thick 7050-T7451aluminum alloy joint was obtained by friction stir welding, and the two-step aging treatment was performed at 121 °C × 5 h + 163 °C × 27 h after welding. Microstructure, hardness profiles and stress corrosion sensitivity of the joint were measured and studied. The results indicate that through the two-step aging, the grain size is coarsened, the age-hardening precipitates and PFZ become wider at the same time, which results in the discontinuous grain boundary; the microhardness of the FSW joints decreased, but the heat-affected zone significantly narrowed, which increased the uniformity of the microhardness of the FSW joints; and the two-stage aging effectively reduced the stress corrosion sensitivity of the FSW joints. The joints with aging treatment were not broken after 60 days, however all the joints without aging treatment were broken within 1 day.

To investigate the influence of temperature field of friction stir welding (FSW) 2219 aluminum alloy thick plate, and to achieve effective prediction of temperature field, the authors establish a three-dimensional numerical simulation model of FSW 18 mm thick 2219 aluminum alloy based on ABAQUS/CEL, considering the morphological characteristics of the tool pin. The simulations of plunging, dwelling, and welding stages are achieved. The distribution of temperature and temperature cycle curve of characteristic points in welding process are obtained. The validity of the simulation results is verified by experiments. The influence of the tool-rotational speed and welding speed on temperature field is explored. The work lays a foundation for the prediction and control of temperature field in FSW medium thickness 2219 aluminum alloy, and provides reference for selection of welding parameters to ensure high quality welding of fuel tank of heavy-lift rocket.

Gas pore is a common defect in brazed joint. It lowers the brazing rate and affects the properties of joint. Experimental results show that the application of unequal-gap brazing seam effectively decreases the amount and volume of gas pores, and increases brazing rate. This paper establishes a force model of unequal-gap brazing seam, and proposes the constitutive relationship between expulsion force and curvature. The force condition of gas bubble in geometrically different brazing seams were calculated, and the results were verified with experiments. The results show that the expulsion force of gas bubble is positively correlated to the curvature of the seam geometry. The gas bubble tends to move towards the direction with large curvature and wider gap. The directional bubble movement is obtained through varying the configuration of gas-liquid interface to meet geometric conditions. Gas bubble accelerates to expulse with arc, hyperbola and cycloid brazing seams, in which the best drainage effects of gas bubble occur for cycloid seams.

Automatic on-line detection of welding deviation based on machine vision is one of the key technologies of arc welding robot tracking welding, in which obtaining high quality weld pool image and accurate welding deviation detection algorithm are two important steps of tracking welding. Through the research and analysis of the weld pool image of gas metal arc welding (GMAW), it was found that the weld pool contains abundant welding information. First, the average gray value of the weld pool image can reflect the interference degree of arc to weld pool image and the heat input of welding process. Secondly, the tip of the weld pool image contour can reflect the center of the groove gap. Finally, the horizontal distance between the center coordinate of the wire contour and the tip coordinate of the weld pool image contour can reflect the welding deviation. On the basis of analyzing the characteristics of weld pool image, this paper proposes a new method of weld seam deviation detection, which includes the collection of weld pool image, image preprocessing, contour extraction and deviation calculation. The results of the tests and analyses showed that the maximum error of the on-line welding deviation obtained was about 2 pixels (0.17 mm) when the welding speed was ≤60 cm/min, and the algorithm was stable enough to meet the requirements of real-time deviation detection for I-groove butt welding. The method can be applied to the on-line automatic welding deviation detection of arc welding robot.

The effect of fiber laser on MIG arc was investigated with 8 mm 7075-T6 high strength aluminum alloy as base material. The arc shape, droplet transfer form and electrical signal in the process of MIG welding and laser-MIG hybrid welding were analyzed. The stability of the hybrid welding process was evaluated by standard deviation analysis. The results show that with the increase of laser power, a large number of laser-induced plasma enters the arc column area, providing more conductive channels, which makes the heat of MIG arc more concentrated and the short circuit transition disappear. Due to the continuous effect of laser, the keyhole becomes a continuous electron emission source, and a stable cathode spot will be formed near the keyhole, which enhances the stability of MIG arc at the base current state. By using the method of standard deviation analysis, the voltage standard deviation of single MIG welding arc and laser-MIG hybrid arc within 4 seconds was calculated. The standard deviation of single MIG arc voltage was 1.05, and the standard deviation of MIG arc voltage in laser-MIG hybrid welding was 0.71–0.86, so the hybrid welding process was more stable.

With the continuous development of high-power electronic devices, the traditional tin-lead brazing materials no longer meet the conditions of use, and sintered nanometal solder paste is promising for a new generation of packaging materials. The mechanism of microstructural changes of nanoparticle sintering during the sintering process has not been well studied at present. Molecular dynamics (MD) simulations can effectively track the diffusion process of metal atoms during the sintering process and help to reveal the dynamic evolution of nanoparticles. This review presents many MD simulations of nanoparticle sintering, including the growth mechanism of nanoparticles, the effect of different sintering parameters on the performance of sintered joints, the connection mechanism between the reinforced phase and nanoparticles and the performance of composite sintered joints. The low temperature and low pressure sintering of nanopaste are still in face of some problems, and MD simulations are very helpful for improving the sintering process and verifying the mechanism of the reinforcing phase.

The finite element simulation software SYSWELD is used to numerically simulate the temperature field, residual stress field, and welding deformation of Q690D thick plate multi-layer and multi-pass welding under different welding heat input and groove angles. The simulation results show that as the welding heat input increases, the peak temperature during the welding process is higher, and the residual stress increases, they are all between 330–340 MPa, and the residual stress is concentrated in the area near the weld. The hole-drilling method is used to measure the actual welding residual stress, and the measured data is in good agreement with the simulated value. The type of post-welding deformation is angular deformation, and as the welding heat input increases, the maximum deformation also increases. It shows smaller residual stress and deformation when the groove angle is 40° under the same heat input. In engineering applications, under the premise of guaranteeing welding quality, smaller heat input and 40° groove angle should be used.

Na₂SiF₆ was used as surface activating flux for laser welding of TC4 titanium alloy. The effect of Na₂SiF₆ on TC4 titanium alloy laser welding was determined by observing the weld surface. The morphological characteristics of the high temperature plasma above the workpiece was observed and analyzed by using high-speed digital camera system. The variation of weld depth,width and microstructure were analyzed by optical microscope. The experimental results show that laser weld of TC4 titanium alloy has good appearance with activating flux of Na₂SiF₆, weld penetration increases by about 0.8%–12%, while weld surface width decrease by about 10%–29%, the depth to width ratio is effectively improved. The inhomogeneity of weld microstructure was improved, and the crystallization direction of β columnar crystals on the upper part of the weld was changed, the grain size and microstructure of the weld were refined by Na₂SiF₆.

The microstructure and mechanical properties of high nitrogen steel (HNS) weld metals prepared under air- and water-cooling conditions are investigated, and the effect of the cooling rate on these properties is discussed. The results indicate that an increase in the cooling rate could significantly increase the nitrogen content in HNS weld metals, especially for weld metals with a nitrogen content of 0.85%. Moreover, increasing the cooling rate could result in an increase in the tensile strength of HNS weld metals, which is found to be strongly dependent on the nitrogen content of the HNS sample. For high nitrogen austenitic stainless steel welding wire with lower nitrogen content, increasing the cooling rate could significantly improve its tensile strength, but a higher cooling rate has no influence on weld metals with nitrogen content less than 0.58%. The tensile strength of the joint reached 850 MPa.

Interconnections in microelectronic packaging are not only the physical carrier to realize the function of electronic circuits, but also the weak spots in reliability tests. Most of failures in power devices are caused by the malfunction of interconnections, including failure of bonding wire as well as cracks of solder layer. In fact, the interconnection failure of power devices is the result of a combination of factors such as electricity, temperature, and force. It is significant to investigate the failure mechanisms of various factors for the failure analysis of interconnections in power devices. This paper reviews the main failure modes of bonding wire and solder layer in the interconnection structure of power devices, and its failure mechanism. Then the reliability test method and failure analysis techniques of interconnection in power device are introduced. These methods are of great significance to the reliability analysis and life prediction of power devices.

Laser beam welding is used to fabricate the 7A52 aluminum alloy plates. Effects of shielding gas and defocusing on porosities are investigated. Porosities are divided into hydrogen porosities and keyhole-induced porosities. With the increasing flow rate of the front shielding gas, the porosity ratio firstly decreases, then increases. The porosity ratio is lowest under the flow rate of 25 L/min. When the flow rate is 30 L/min, the porosity ratio is higher because the large flow rate can affect the stability of the keyhole. The porosity ratio is also higher when the flow rate is less than 25 L/min because the protection is weakened. With the increase of the defocusing, the porosity ratio firstly decreases, then increases. When the defocusing is –2 mm, the porosity ratio is lowest. When the defocusing is more than 0 mm or less than –4 mm, the porosity ratio is higher due to the movement of the instable keyhole.

Metal inert gas (MIG) welding was conducted with 12 mm thick 6082-T651 aluminum alloy plate to investigate the microstructure and mechanical properties of welded joint. The microstructure and element distribution of weld seam were characterized by electron backscattered diffraction (EBSD) and electron probe microanalysis (EPMA). The weld seam has typical cube texture ({001}<100>) characteristics. The closer to the center of weld seam, the weaker the texture feature, the higher the proportion of high-angle grain boundaries. The average tensile strength of joint was 232 MPa which is up to 72% of 6082 aluminum alloy base metal, and the bending angle for the root bend test sample reached 90° without cracks. The lack of strengthening phase and the existence of welding pores and inclusions in the weld seam caused the degradation of mechanical properties of resultant joint. The microhardness increased from the weld center to the base metal, but the overaging zone caused by welding thermal cycle was softening part of the joint, which had lower hardness than the weld seam.

The growing interest in additive manufacturing of GH4169 alloy was accompanied by the demand on spherical GH4169 powders with high performance. The powder particles were treated by radio frequency plasma with the different feeding rates. The microstructure and morphology, the particle size distribution of as-treated powders were studied by scanning electron microscopy and laser particle size analysis. It was demonstrated that GH4169 powders with extremely fine followability were obtained by radio frequency plasma spheroidization technology. With the same plasma parameters, the spheroidization efficiency of the particles varied with the feeding rates. When the rate of the powder feeding rates was too small, the excessive absorption of the heating by the powders caused vaporization, then the collection decreased. When the feeding rates was too large, the powder particles were insufficiently absorbed, resulting in defects in the powders. The microstructure of the as-treated spherical particles was mainly cell crystals, columnar crystals, and even microcrystals. Under the suitable plasma parameters, the resulting powders haved a slightly increased average particle size, excellent spheroidization, surface smoothness, followability, and bulk ratio.