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Previously, we successfully established a highly functional, three-dimensional hepatocyte-like cell (3D-HLC) model from adipose-derived mesenchymal stem cells (ADSCs) via a three-step differentiation protocol. The aim of the present study was to investigate whether generating hepatocyte-like organoids (H-organoids) by adding endothelial cells further improved the liver-like functionality of 3D-HLCs and to assess H-organoids' immunogenicity properties. Genes representing liver maturation and function were detected by quantitative reverse transcription–PCR analysis. The expression of hepatic maturation proteins was measured using immunofluorescence staining. Cytochrome P (CYP)450 metabolism activity and ammonia metabolism tests were used to assess liver function. H-organoids were successfully established by adding human umbilical vein endothelial cells at the beginning of the definitive endoderm stage in our 3D differentiation protocol. The gene expression of alpha-1 antitrypsin, carbamoyl–phosphate synthase 1, and apolipoprotein E, which represent liver maturation state and function, was higher in H-organoids than non-organoid 3D-HLCs. H-organoids possessed higher CYP3A4 metabolism activity and comparable ammonia metabolism capacity than 3D-HLCs. Moreover, although H-organoids expressed human leukocyte antigen class I, they expressed little human leukocyte antigen class II, cluster of differentiation (CD)40, CD80, CD86, and programmed cell death ligand 1, suggesting their immunogenicity properties were not significantly upregulated during differentiation from ADSCs. In conclusion, we successfully established an H-organoid model with higher liver-like functionality than previously established 3D-HLCs and comparable immunogenicity to ADSCs. [ABSTRACT FROM AUTHOR]

The article presents the discussion on characterizing and engendering authenticity of being human and humanness. Topics include exploring interpretations of human completeness and human wholeness as transhumanist perspectives influencing nursing and healthcare; and explaining transhumanist medicine including neuroenhancements, body enhancements, genetic engineering, and antiaging technologies.

The tumor microenvironment (TME), which is composed of various cell components and signaling molecules, plays an important role in the occurrence and progression of tumors and has become the central issue of current cancer research. In recent years, as a part of the TME, the peripheral nervous system (PNS) has attracted increasing attention. Moreover, emerging evidence shows that Schwann cells (SCs), which are the most important glial cells in the PNS, are not simply spectators in the TME. In this review article, we focused on the up-to-date research progress on SCs in the TME and introduced our point of view. In detail, we described that under two main tumor-nerve interaction patterns, perineural invasion (PNI) and tumor innervation, SCs were reprogrammed and acted as important participants. We also investigated the newest mechanisms between the interactions of SCs and tumor cells. In addition, SCs can have profound impacts on other cellular components in the TME, such as immune cells and cancer-associated fibroblasts (CAFs), involving immune regulation, tumor-related pain, and nerve remodeling. Overall, these innovative statements can expand the scope of the TME, help fully understand the significant role of SCs in the tumor-nerve-immune axis, and propose enlightenments to innovate antitumor therapeutic methods and future research. [ABSTRACT FROM AUTHOR]

A laser penetration welding-brazing combined with Cold Metal Transfer (CMT) arc, was proposed to improve weld shape and interfacial reaction inhomogeneity of 5052 aluminum alloy and Q235 low carbon steel with ER5356 welding wire in butt joint. The effects of wire feed speed, beam offset and welding speed on weld shape, interfacial microstructures and tensile strength of joints was studied. This method improved the undercut defect existed in butt laser welding-brazing, obtained well-formed joints and promoted the uniform distribution of the interface reaction. The interfacial intermetallic compounds (IMCs) layer consisted of Fe 2 Al 5 and Fe 4 Al 13 and the thicknesses were controlled to 3-5 μm. Microstructures of weld seam was composed of α-Al and Al 3 Mg 2. The brittle IMCs layer thickened and then the tensile strength decreased with increasing the wire feed speed. The thickness of the IMCs layer decreased but weld shape became worse when the welding speed or the offset increased. The tensile strength increased first and then decreased. The highest tensile strength reached higher than 80 MPa and the joint fractured in IMCs layer along the interface. [ABSTRACT FROM AUTHOR]

Background: Cholangiocarcinoma is one of the most deadly malignant tumors characterized by a tendency of local invasiveness and metastasis at the early phase, high recurrence rate, and difficulty in treatment. Alpha7-nicotinic acetylcholine receptor (α7-nAChR) is highly expressed in a variety of tumors, including cholangiocarcinoma, and may promote tumor progression, but the mechanisms are largely unknown.Aims: Our study is the first to expound upon the role that α7-nAChR plays in cholangiocarcinoma.Methods: We assessed 50 human cholangiocarcinoma tissue samples and 20 normal biliary samples using immunohistochemical staining to find the correlation between α7-nAChR expression and clinicopathological characteristics. We used human cholangiocarcinoma cell lines QBC939 and RBE and α7-nAChR gene knockdown RBE cell lines generated by shRNA lentivirus transfection to investigate the biological functions of α7-nAChR in proliferation, apoptosis, migration, and invasiveness in vitro. Further, western blotting was used to detect apoptosis and epithelial-mesenchymal transition (EMT)-related signaling proteins. Cholangiocarcinoma xenografts in nude mice were used for tumorigenicity assays in vivo.Results: The expression of α7-nAChR was high in cholangiocarcinoma tissues and was closely related to a shorter survival time in patients. α7-nAChR knockdown decreased cell proliferation ability, increased early apoptosis, and weakened cell migration and invasion. Apoptosis-related proteins and components of the EMT process were altered after α7-nAChR knockdown. Moreover, nude mice xenograft experiments confirmed that α7-nAChR could promote cholangiocarcinoma in vitro.Conclusions: Overexpression of α7-nAChR induces cholangiocarcinoma progression by blocking apoptosis and promoting the EMT process. As an effective molecular biomarker and prognostic factor, α7-nAChR is a promising therapeutic target in cholangiocarcinoma. [ABSTRACT FROM AUTHOR]

Abstract Intergranular liquid metal penetration, which is detrimental to the integrity of welded structures, has been widely investigated. Its mechanisms are now more clearly understood, but the suppression method is limited to optimizing processing parameters. In this paper, a metallurgical suppression technique by building an interfacial ferrite band to prevent intergranular liquid Cu penetration of solid steel was proposed. A ternary chemical potential prediction model was established and predicted that Si in liquid copper can accumulate at the interface and diffuse into steel during the interaction between molten Si-containing Cu and solid steel. This interaction can induce the formation of a ferrite band with a high resistance to intergranular liquid copper penetration of solid steel. A model for interfacial ferrite band formation based on Si diffusion during the interaction between solid steel and Si-containing molten copper was proposed and experimentally verified by welding-brazing copper to steel with Si-containing copper wire. The results indicated that long-range intergranular penetration was effectively suppressed, and harmless micropenetration appeared between the ferrite band and weld. The intergranular micropenetration mechanism is considered a grain boundary liquidation phenomenon induced by Si diffusion, differing from classical wetting theory. Graphical abstract Image 1 Highlights • A ternary chemical potential model was established to predict Si diffusion. • Si accumulation along the interface led to interfacial ferrite band formation. • Interfacial ferrite layer suppressed liquid intergranular Cu penetration of steel. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The 3003 aluminum alloy was welded to the pure titanium by a collision welding method called as vaporizing foil actuator welding (VFAW). By designing a groove die with special angles, it was found that the interfacial wave morphology transformed from irregular to regular, and recovered to irregular with increasing the angle. The best impact angle range was from 16°to 24° to generate the regular interfacial wave. By building the VFAW experiments with parallel standoff gaps, influence of standoff and input energy on interfacial morphology and mechanical properties were investigated. To generate obvious interfacial wave, the standoff was higher than 0.93 mm at constant input energy of 6.4 kJ, and the input energy was from 6.4 kJ to 8.0 kJ at constant standoff of 0.93 mm. A small amount of intermetallic compounds only appeared at troughs of the wavy interfaces with the maximum size of 3–6 μm. The interface has higher strength than the aluminum base metal in the range of the optimized processing parameters. The influence of the collision angle on the interfacial wave was clarified from the view of fluid dynamics. The relationship between the mechanical properties and the interfacial wave was discussed based on the impact velocity measured by a photonic Doppler velocimetry (PDV) method. [ABSTRACT FROM AUTHOR]

Light-emitting diode (LED) irradiation has been used in the differentiation of mesenchymal stem cells into a variety of cell types. This study investigated the effect of green LED (GLED) irradiation on the differentiation of adipocyte-derived mesenchymal cells into hepatocyte-like cells (HLCs) and the mechanism of its action. HLCs in the hepatocyte maturation phase were irradiated with GLED (520 nm, 21 W/m2, 5 min/day for 10 days). The cells were then assessed for expression of hepatocyte maturity genes and opsin 3 (OPN3), hepatocyte function, viability, apoptosis, and levels of reactive oxygen species (ROS), intracellular adenosine triphosphate (ATP) and calcium ions (Ca2+). GLED irradiation increased Alpha-1 antitrypsin and Ornithine transcarbamylase gene expression, promoted Cytochrome P450 3A4 activity and urea synthesis, and elevated intracellular ROS, ATP and Ca2+ levels. OPN3 expression was significantly more upregulated in GLED-irradiated HLCs than in the non-irradiated HLCs. No significant difference in cell viability or apoptosis was observed between GLED-irradiated and non-irradiated HLCs. GLED irradiation can promote hepatocyte maturation and functions through OPN3. GLED irradiation also stimulated mitochondrial function via Ca2+/ATP/ROS activation. GLED irradiation has potential to support cell-based transplantation in patients. [ABSTRACT FROM AUTHOR]

A novel thermophysical simulation method to precisely control the reaction conditions was designed to investigate molten aluminium/solid steel interfacial reactions. The reaction layers between the materials were investigated by high-resolution transmission electron microscopy assisted by advanced focused ion beam technology. For the first time, fibrous-ordered Fe 2 Al 5 and Fe 4 Al 13 intermetallics induced by an order–disorder transformation appeared in the disordered substrates of Fe 2 Al 5 and Fe 4 Al 13 , respectively. High-density planar defects composed of stacking faults and twinnings were found inside the Fe 4 Al 13 grains. The (001) twinning as a type of growing twin was considered to be the sole operating mechanism during the solid/liquid interfacial reaction. [ABSTRACT FROM AUTHOR]

An overlap titanium-on-aluminum configuration based on laser penetration welding was designed to suppress the formation of intermetallic compounds. Weld surface appearance, weldgeometry, microstructure, and mechanical property of the joint were investigated. The collaps of upper liquid titanium closes keyhole filled with boiling aluminum vapor, which induces welding spatter. Optimizing processing parameters could control the welding spatter to some extent. Weld geometry is characterized by depth of the weld loss, depth of the penetration of titanium into aluminum and width of joining, which depends on processing parameters strongly. The overlap titanium-on-aluminum configuration can suppress the formation of intermetallic compounds inside Ti weld. Interfacial reaction appears between Ti weld and Al, and the reaction layers are composed of TiAl and TiAl. The banded structures with TiAl were found inside Ti weld. Tensile capacity of the joint increases firstly and then decreases with increasing laser power or decreasing welding speed, depending on weld geometry and interfacial reaction. Moreover, there are two broken modes of the joints, which are fractured in interface and in Ti weld, respectively. When joints fracture in the Ti weld, the joint has the higher tensile property, up to 184 N/mm. [ABSTRACT FROM AUTHOR]

Different from traditional collision welding methods in driving principle, vaporizing foil actuator welding (VFAW) was developed to weld 3003 aluminum alloy (Al) to 4130 steel (Fe). The interfacial morphology and microstructures of VFAW were investigated, and the effect of the impact angle on interfacial morphology was analyzed through a groove die with a special angle. Results showed that irregular interfacial waves were formed between Al and Fe, confirming that the VFAW achieved metallurgical bonding. The range of impact angle forming interfacial irregular waves was from 8° to 24°, which meant the impact welding of 3003 Al to 4130 Fe has relatively wide weldable range of collision angle. The formation of irregular interfacial waves considered to be related to match between the density of the flyer and the ultimate static strength of the target. A very thin layer with intermetallic compounds, composed of continuous Al 86 Fe 14 and massive Fe 4 Al 13 and FeAl, was formed in the trough of interfacial waves. The layer with intermetallic compounds was formed by very thin liquid metal, which was the residual liquid metal of the jet flow along the interface. The highest anti-shear capacity of the joint exceeds 200 N/mm. [ABSTRACT FROM AUTHOR]

Dissimilar metal welding of Q235 low carbon steel and 5052 aluminum alloy was carried out by a single/dual-beam laser in a steel-on-aluminum overlap configuration with a copper interlayer. The weld appearance, microstructure, and fracture behavior of the joints made by the single/dual-beam laser welding were investigated comparatively. The results showed that dual-beam laser welding, compared with single-beam laser welding, had better process stability which made better weld appearance and bigger effective joining width which enhanced tensile capacity. With a copper interlayer, a contact reaction zone appeared between the copper interlayer and aluminum matrix, which enlarged effective joining zone. The microstructures of the welding joint welded by a single/dual-beam laser were composed of the ligulate fusion zone with Fe-Al interface and the contact reaction brazing zone with Al-Cu interface. The Fe-Al interface mainly consisted of α-Al and AlCu eutectic structure, FeAl, FeAl, and a certain amount of Al-Cu intermetallics, FeAl and FeAl. The Al-Cu interface mainly consisted of eutectic phase AlCu and metastable phase of Al-Cu intermetallics. The tensile property was enhanced by a dual-beam laser, and the addition of the copper-foil interlayer might improve the metallurgical reaction of interfacial reaction region and promote the load-carrying ability of weld joint. An ideal joint with fewer defects could be obtained when the welding speed is 0.9-1.25 m/min of dual-beam laser welding and 1.5-1.75 m/min of single-beam laser welding. [ABSTRACT FROM AUTHOR]

The microstructures and mechanical property of stainless steel/copper laser welding were investigated by controlling the processing parameters of welding speed and laser power as well as the offset and incline angle of the laser beam in the direction of the stainless steel. The joining mode could be controllably transformed to welding–brazing from fusion welding. The welding–brazing mode joins liquid stainless steel to solid copper, whereas the fusion zone mode joins stainless steel and copper by melting and mixing both metals. Offsetting and inclining the laser beam in the direction of the stainless steel can effectively suppress the melting of the copper and ensure the joining occurs via welding–brazing. The grains of heat-affected zone (HAZ) on the side of the copper grow significantly. Liquid separation reactions induce spherical particles with copper and some bigger spherical particles with copper contained smaller spherical particles with stainless steel. The highest tensile strength of the joint reaches 260 MPa. The joint exhibited three typical modes of fracture: the interface, the heat affected zone (HAZ) and the fusion zone, depended on the processing parameters that were used. The tensile strength is weakly dependent on melting of the copper, but melting of the copper induces a decrease in the joint toughness. [ABSTRACT FROM AUTHOR]

Sudachitin is a polymethoxylated flavone found in the peel of Citrus sudachi, a unique specialty citrus fruit in Tokushima Prefecture, Japan. Previous reports have demonstrated that sudachitin has anti-inflammatory and metabolic regulatory activities. However, to the best of our knowledge, no studies have explored whether sudachitin can act as an antitumor therapeutic agent by regulating metabolic functions in the tumor microenvironment. In the present study, cell proliferation and cytotoxicity assays were used to determine whether sudachitin inhibited the in vitro growth of liver cancer and pancreatic carcinoma, cholangiocarcinoma and colorectal cancer cells and to compare its toxicity against normal fibroblasts and induced cancer-associated fibroblasts (CAFs). Using lactate assays and reverse transcription-quantitative PCR, the effects of sudachitin on glycolysis in CAFs were investigated. The effects of CAFs on malignant tumor cells were evaluated in vitro using cell proliferation, wound healing and invasion assays. As result, sudachitin inhibited various types of tumor cells with different half-maximal inhibitory concentrations. Treatment with 50 µM sudachitin for 48 h suppressed tumor and CAFs proliferation but was not cytotoxic against normal fibroblasts. This dose also inhibited glycolysis in CAFs and, thus, diminished their pro-tumorigenic activities. Overall, the present study revealed that sudachitin has promise as a safe and widely available natural antitumor adjuvant. [ABSTRACT FROM AUTHOR]

A double-ceramic-layer (DCL) thermal barrier coatings (TBC) of La 2 (Zr 0.7 Ce 0.3 ) 2 O 7 /8YSZ (LZ7C3/8YSZ) was prepared by atmospheric plasma spraying (APS). The phase structure, composition, thermal conductivity, surface and cross-sectional morphologies, adhesion strength and thermal shock behavior of the LZ7C3/8YSZ coating were investigated. The X-ray diffraction pattern showed that the phase structures of top coat LZ7C3 was different from the powder for spraying, which consists of pyrochlore LZ and fluorite LC structures. Main peaks between LZ and LC in as-sprayed LZ7C3 have almost overlapping diffracted angles and approximately equal diffracted intensity. Thermal shock lifetime and adhesion strength of the DCL LZ7C3/8YSZ coating are enhanced significantly as compared to single LZ7C3 coating, and are very close to that of single 8YSZ coating. The mechanisms of performance improvement are considered to be effictive reduction of stress concentration between substrate and LZ7C3 coating by 8YSZ buffer effect, and the gentle thermal gradient initiated at the time of quenching in water. The DCL LZ7C3/8YSZ coating has lower thermal conductivity than 8YSZ, which was only 25% of 8YSZ bulk material and 65% of 8YSZ coating by APS. [ABSTRACT FROM AUTHOR]

• The Al/Fe laser welding-brazing joints were produced by five different filler wires. • Thecharacteristics of Al/Fe joints with five different filler wires were compared. • The influence of laser offset on joint characteristics was studied in detail. The purpose of this paper is to provide the gist for the selection of filler wire during the laser welding-brazing of Al to steel. A comprehensive comparison of laser welding-brazing 5052 aluminum alloy to unbeveled galvanized steel using pure Al, AlSi5, AlMg5, AlCu6, and ZnAl2 filler wires were conducted with varied laser beam offset. The comparison was carried out in terms of weld formation, interfacial microstructures, and mechanical properties. The results show that the fluidity of liquid filler is Pure Al < AlSi5 < AlMg5 < AlCu6 < ZnAl2. Too small or too large fluidity will lead to poor weld formation. The interfacial intermetallic compound consisted of layered Fe 2 Al 5 and scattered FeAl 3 when pure Al, AlMg5, and AlCu6 filler wires were used. When pure Al filler wire was used, cracks were most likely to occur in the reaction layer. The other four filler wire all improved the crack resistance. The thickness of the reaction layer significantly decreased when AlSi5 filler wire was used. Si element was found as a solid solution in the reaction layer to form Fe 2 (Al, Si) 5 and Fe(Al, Si) 3. A large amount of FeZn 10 was mixed between Fe 2 (Al, Zn) 5 when using ZnAl2 filler wire. The order of maximum tensile strength of the joints using different filler wires was AlSi5 > AlMg5 > AlCu6 > ZnAl2 > pure Al. The fracture of the joints all occurred at the brittle intermetallic layers when five different filler wires were used. [ABSTRACT FROM AUTHOR]

Highlights: [•] The laser direct butt welding of titanium alloy to stainless steel is realized. [•] The interfacial microstructures of the joints are confirmed. [•] The weldability is better when laser beam is offset toward titanium than steel. [•] The highest tensile strength of the joint reaches to 150MPa. [ABSTRACT FROM AUTHOR]

Abstract: Laser penetration welding of a steel-on-aluminium overlap configuration with Ni-foil interlayer was investigated. The steel-on-aluminium overlap configuration prevented the formation of intermetallic compounds inside the fusion zone. A new intermetallic compound Al0.9Ni1.1 was discovered to have formed between the fusion zone and Al alloy, in addition to FeAl3, compared to a joint with no Ni-foil interlayer. The Ni-foil interlayer improved the metallurgical reaction at the interfacial zone, which decreased the microhardness of interfacial intermetallic compounds and enhanced the toughness of the joint. The tensile property of the joint with Ni-foil interlayer is higher than that of the joint without Ni-foil interlayer. [Copyright &y& Elsevier]

Abstract: La2Zr2O7 has high melting point, low thermal conductivity and relatively high thermal expansion which make it suitable for application as high-temperature thermal barrier coatings. Ceramics including La2Zr2O7, (La0.7Yb0.3)2(Zr0.7Ce0.3)2O7 and (La0.2Yb0.8)2(Zr0.7Ce0.3)2O7 were synthesized by solid state reaction. The effects of co-doping on the phase structure and thermophysical properties of La2Zr2O7 were investigated. The phase structures of these ceramics were identified by X-ray diffraction, showing that the La2Zr2O7 ceramic has a pyrochlore structure while the co-doped ceramics (La0.7Yb0.3)2(Zr0.7Ce0.3)2O7 and the (La0.2Yb0.8)2(Zr0.7Ce0.3)2O7 exhibit a defect fluorite structure, which is mainly determined by ionic radius ratio r(Aav. 3+)/r(Bav. 4+). The measurements for thermal expansion coefficient and thermal conductivity of these ceramics from ambient temperature to 1200°C show that the co-doped ceramics (La0.7Yb0.3)2(Zr0.7Ce0.3)2O7 and (La0.2Yb0.8)2(Zr0.7Ce0.3)2O7 have a larger thermal expansion coefficient and a lower thermal conductivity than La2Zr2O7, and the (La0.2Yb0.8)2(Zr0.7Ce0.3)2O7 shows the more excellent thermophysical properties than (La0.7Yb0.3)2(Zr0.7Ce0.3)2O7 due to the increase of Yb2O3 content. [Copyright &y& Elsevier]

Abstract: The mechanical behavior and superplastic deformation mechanism of a laser-welded Ti–6Al–4V alloy joint were investigated. Uniaxial tensile tests were performed on welded specimens at 870–920°C temperature and 10−3 to 10−1 s−1 strain rate. The microstructural evolution of the weld zone was observed under the strains of 43%, 143%, 229%, and 387%. The laser-welded joint was found to have good superplasticity under a suitable strain rate; the highest joint elongation reached 397%. Superplastic deformation in the weld zone accompanied the globularization of the as-welded microstructure. Continuous globularization ensured a good superplasticity of the laser-welded joint. As a major cause of the globularization of lamellar structures in the weld zone, the stress activated the diffusion of Al atoms by changing the chemical potential at the boundaries of the α phase. Consequently, α→β phase transformation occurred. The globularization of the as-weld microstructures was considered to be governed by this transformation and the development of grain boundary sliding. [Copyright &y& Elsevier]

Abstract: Heterogeneous interfacial reactions were easily found along the Ti/Al interface due to high temperature gradient during laser welding–brazing of Ti/Al dissimilar alloys. To improve the nonhomogeneity, relative uniform energy distribution of laser beam and appropriate groove were attempted. The effects of these attempts on the nonhomogeneity of interfacial reactions were investigated by finite element method (FEM) numerical simulation and experimental validation. The results indicate that the V-shaped groove can make the interface roughly parallel to the isotherm of the temperature field. Moreover, the rectangular spot laser can further improve homogenization of the interfacial reaction along the interface in comparison with circular spot laser. Tensile test results show that the combination of rectangular spot laser welding–brazing and V-shaped groove can effectively control the fracture of Ti/Al joints in the seam in a wide processing parameters window, and the average tensile strength reaches 278MPa. [Copyright &y& Elsevier]

Abstract: Joining mechanism of Ti/Al dissimilar alloys was investigated during laser welding–brazing process with automated wire feed. The microstructures of fusion welding and brazing zones were analysed in details by transmission electron microscope (TEM). It was found that microstructures of fusion welding zone consist of α-Al grains and ternary near-eutectic structure with α-Al, Si and Mg2Si. Interfacial reaction layers of brazing joint were composed of α-Ti, nanosize granular Ti7Al5Si12 and serration-shaped TiAl3. For the first time, apparent stacking fault structure in intermetallic phase TiAl3 was found when the thickness of the reaction layer was very thin (approximately less than 1μm). Furthermore, crystallization behavior of fusion zone and mechanism of interfacial reaction were discussed in details. [ABSTRACT FROM AUTHOR]

Abstract: Influence of interfacial reaction on crack initiation and propagation in Ti/Al joint by laser welding–brazing (LWB) was investigated to obtain strong joints. According to in situ observation of crack initiation and propagation and analysis of fracture surface, the effects of different reaction layer including interfacial layer with insufficient interfacial reaction, lamella-shaped morphology, cellular/serration-shaped morphology, club-shaped morphology, and thick continuous morphology on crack initiation and propagation was discussed. It was found that the joint with lamella-shaped, cellular or serration-shaped, club-shaped interfacial layer has the highest mechanical property in current study. [Copyright &y& Elsevier]

A rectangular spot laser welding–brazing method was developed to join butted Ti/Al dissimilar alloys. In order to evaluate effects of heat input on mechanical property of the joints, microstructure of the joints were characterized. TiAl3 intermetallic compounds (IMCs) were found at the joint interface in the case of low-heat input and TiAl3, TiAl, Ti5Si3, and Ti3Al IMCs were observed at high-heat input. Results of tensile test showed that the joints fracture in the fusion zone under the condition of low-heat input and in the interfacial reaction layer or the fusion zone with a mass of porosities at high-heat input. In addition, tensile strength of specimens broken at the fusion zone is higher obviously than that at the interface or the fusion zone with a mass of porosities, and tensile strength of the joints is up to 290 MPa. [ABSTRACT FROM AUTHOR]

• The low melting point Sn-Zn filler wire was used to achieve the laser butt joining of Al/steel. • Influence of laser power on microstructure and properties of Al/steel joint was investigated. • The unique phenomenon of detached of IMCs layer was discovered. Butt joining of 5052 aluminum alloy and Q235 low carbon steel was achieved using laser beam welding with Sn-30Zn filler wire. The weld formation, microstructures, and mechanical property were investigated with varied laser power. The results show that joining of 5052 Al/Q235 steel dissimilar metals in a butt configuration by laser beam welding with Sn-30Zn filler wire is feasible. The solid solution interface formed at the aluminum side and the reaction layer formed at the steel side. With increasing laser power, the joining mode transformed from brazing to welding-brazing due to the melt of aluminum alloy. The thickness of the interfacial intermetallic compounds (IMCs) layer was also increased with laser power. However, when the laser power was 1200 W, the thickness of the interfacial IMCs layer sharply decreased due to the detachment of the IMCs layer. The fracture of the joint occurred at the steel interface and partially through the weld seam on the top surface. The fracture surface was characterized by both brittle and ductile fracture. When the joints were obtained at the laser power of 800 W and 1200 W, the tensile strength reached 79 MPa and 78 MPa, respectively. Furthermore, the formation mechanism of microstructures and its influence on mechanical property was discussed. [ABSTRACT FROM AUTHOR]

Abstract: Si-doped TiO2 nanoparticles were prepared via a solvothermal method and were sensitized by the Fe-quinoline complexes (HQSI) to improve the visible light photocatalytic activity. The used HQSI had a narrow band gap of 1.54eV and showed strong visible light absorption. HQSI can transfer photoelectrons to the conduction band of TiO2 and be regenerated by the electron injection from Rhodamine B. After sensitization, the Si-doped TiO2 exhibited stronger absorption in the visible region and showed higher visible-light photocatalytic activity for the degradation of Rhodamine B in an aqueous solution than the simple Si-doped TiO2 and sensitized commercial TiO2. [Copyright &y& Elsevier]

The welding characteristics of 7075 aluminum alloy and DP980 dual-phase steel sheet were systematically studied by the friction plug-riveting spot welding technology. The effects of different welding parameters on the weld formation, tensile strength, and microstructure of welded joints were analyzed. The complete metallurgical joining interface was formed between the rivet and steel plate. A partial metallurgical joining interface was formed between the circumferential surface of the rivet shaft and the aluminum alloy close to the steel sheet. However, the position of the rivet head did not form a metallurgical joining with the aluminum alloy. During the welding process, the area of the rivet interface underwent severe plastic deformation by frictional heat and down pressure; thus, there was a violent interaction between the plastically deformed metal and the surrounding aluminum alloy. The molten aluminum infiltrated into the rivet at the most of sample joints. The penetration of aluminum had a negative effect on the shear load. The maximum shear load of the joint was 14.374 kN. There were two types of fractures: the internal fracture of the rivet and the fracture of the steel/steel friction interface. When the fracture mode was an internal fracture of the rivet, the shear load was generally greater than the steel/steel friction interface. [ABSTRACT FROM AUTHOR]

A novel method for preparing or repairing titanium-clad steel plates is proposed in this paper. Molten titanium powder is deposited onto the surface of Q235 steel using plasma transferred arc powder surfacing, creating metallurgical bonding of Ti/steel dissimilar metals. The influence of welding current and welding speed on the appearance, microstructure, and mechanical properties of the titanium-clad steel plate was studied. The results showed that welding parameters directly affect the heat input of the titanium surfacing layer during welding, changing the microstructure and strength of the titanium surfacing layer. In the low heat input mode, the interface microstructures consist of a TiFe layer and a TiFe2 layer. With increasing heat input, the phenomenon of intermetallic compound separation at the interface disappeared. Additionally, the surfacing was covered by a layer of eutectic structure instead of the ideal pure titanium. The brittle phase is the main factor limiting the shear resistance of titanium-steel welded joints. Under the shear load, the joint cracks mainly initiated in the intermetallic compound region and fractured with a brittle mode. The maximum shear strength was 142.05 MPa. Based on the analysis of interface microstructures, the bonding mechanism of titanium-clad steel plates made by PTA powder surfacing was revealed. [ABSTRACT FROM AUTHOR]

The growth kinetics of intermetallic compounds (IMCs) generated by initial interfacial reaction (interaction time < 10 s) between solid steel and molten aluminum was investigated using a thermophysical simulation method. According to the morphology evolution of the η (Fe 2 Al 5 ) and θ (Fe 4 Al 13 ) phase layers in the isothermal experiments in seconds, it is confirmed that the reaction diffusion controls the η phase growth and the θ phase precipitates from the liquid phase during cooling. The growth kinetics models of the η phase maximum and average thickness are proposed as well. The results showed that the maximum growth was governed by the interfacial reaction, whereas the average thickness was governed by a diffusion and interfacial reaction process. Considering the application of the kinetics model in welding-brazing of Fe/Al dissimilar metals, a mathematical model to predict the average thickness of η phase was established using the finite difference method in thermal cycles as well. The predicted results are consistent with the experimental results, indicating that the model is of good accuracy. [ABSTRACT FROM AUTHOR]

An in situ water quenching method was used to explore the microstructure evolution and reaction mechanism of Ti–Si–C agglomerates during reactive thermal spraying. The quenched powders exhibit a melting process from outside to inside and small particles to large ones, forming complete droplets with increasing spray distance. The formation of the liquid phase is the basis of the reaction; once the liquid phase is formed, reactions begin to form new phases (TiC and Ti 5 Si 3). The melting point of the new phase and the temperature of the droplet determine the formation mechanism and morphology of the new phase in the coating. As the melting point is higher than the droplet temperature, the new phase, TiC, grows to a large submicron size in flight. When the melting point is lower than the droplet temperature, like Ti 5 Si 3 , it dissolves into the liquid phase and re-precipitates in nanometer size at impact. Moreover, the droplet surface absorbed and dissolved O element from the atmosphere, and thus Ti 3 O coexisted with Ti 5 Si 3 in lamellae of coatings. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Organic heterostructures that can integrate the physiochemical properties of two or more substances have attracted widespread attention in the field of optoelectronics. However, the epitaxial growth process between different organic material molecules is unpredictable, and the precise synthesis of organic heterostructures is still particularly challenging. Herein, through the synergy approach of polymorphism and cocrystal engineering, a series of organic branched heterostructures have been successfully prepared. Interestingly, by simply adjusting the solvent ratio, different crystalline phases of perylene microplates can be epitaxially grown on the perylene‐OFN cocrystal microwires, which provides a feasible approach for the preparation of organic heterostructures. Meanwhile, these as‐prepared organic branched heterostructures can realize multi‐channel and multi‐color emission, and act as optical logic gates, which promotes the multifunctional integrated optoelectronics. [ABSTRACT FROM AUTHOR]

The influences of the interface morphologies upon the stress distribution in the double-ceramic-layer thermal barrier coating (DCL-TBC) have been mainly studied in our present article using the finite element method. The two important interfaces in the DCL-TBC, which are interface #1 (the interface between two ceramic layers) and interface #2 (the interface between the inside ceramic layer and the bond coat (BC)), are modeled as a sinusoidal wave with considering different values of the amplitude.Results show that the interface #1 has important influence upon the stress of the top ceramic layer. Especially, in the edge of the model, the rougher interface can relief the high stress level of the top ceramic layer caused by the edge stress concentration. Similarly, the influence of the interface #2 upon the stress of different parts of the thermal growth oxide layer has also been studied. [ABSTRACT FROM AUTHOR]

The Double-Ceramic-Layer Thermal Barrier Coating (DCL-TBC) consists of a top ceramic layer (TC1), an inside ceramic layer (TC2), bond coat (BC) and alloy substrate. The top ceramic layer is made by new ceramic materials which has the lower thermal conductivity, such as LZ, LZ7C3, LMA etc. Although these materials have good high temperature performance and thermal insulation properties, their thermal expansion coefficients are very low which cause higher degree of mismatch with material properties of alloy substrate. The behavior of the stress buffer effect of the layer of TC2 is investigated aiming at the DCL-TBC with the two ceramic layers as LZ7C3(TC1) and 8YSZ(TC2). A FE model of the DCL-TBC is established and the stress of the TC1 during the thermal cycles is calculated. Results show that the layer of TC2 has the behaviors of stress buffer effect on reducing the stress of TC1 and reducing the influence of the TGO growth upon the stress of TC1. The inner mechanism of the stress buffer effect is investigated based on the influence of the thermal expansion coefficient ρ of the TC2 layer. Results show that the TC1 layer varies with the TC2 layer, having different thermal expansion coefficients; and the stress buffer effect is dominant, affected by the thermal expansion coefficients of the TC2 layer. The thermal expansion coefficient should be neither too large nor too low; if its values are too low or too large, the stress levels of TC1 are all high. The reasonable range of the thermal expansion coefficient is investigated. Aiming at the DCL-TBC with the two ceramic layer thicknesses as 150μm, the reasonable range of the thermal expansion coefficient of TC2 is from 10.35°C−1 (×10−6) to 10.887°C−1 (×10−6). [ABSTRACT FROM AUTHOR]

The Double-Ceramic-Layer Thermal Barrier Coating (DCL-TBC) consists of a top ceramic layer, an inside ceramic layer, bond coat (BC) and alloy substrate. The introduction of TC2 has the effect of stress buffer to TC1, which causes the stress of TC1 decreased. In this situation, the typical material parameters ρ and E of the inside ceramic layer will have great influence on the stress distribution and ultimate life of the DCL-TBC. Based on this, the first part of the present paper is to investigate the effect of the typical material parameters ρ and E of the TC2 on stress distribution in the DCL-TBC with the thickness ratio of TC1 and TC2 as 150μm–150μm, using the finite element method. From mass calculation, the influences of the material parameters ρ and E upon the stresses of TC1 and TGO are presented in the paper. Secondly, the typical material parameters ρ and E of the TC2 is optimized and selected based on the optimization criteria which are “the stress of the TC1 is in safe state” and “the TGO has the lowest stress level”. Aiming at the criterion based on the safety of the TC1, “general safety region of E–ρ” and “E–ρ general safety boundary” are concluded in the stress map of E–ρ. Based on the criterion of the lowest stress level in TGO, it has been concluded that the point of 47.796–10.8029 is the best point of E–ρ, i.e. the DCL-TBC has the best life if the modulus E and thermal expansion coefficient ρ of the inside ceramic layer are 47.796GPa and 10.8029/°C(×10−6). [ABSTRACT FROM AUTHOR]

Brittle Mo Fe intermetallic compounds (IMCs) are usually fatal for the joining of Mo and steel. In the present work, Ni-free joining of Mo and stainless steel was successfully achieved by laser welding with Cu Ti filler metal. The entry of Mo element into the weld seam and the formation of Mo Fe IMCs was significantly suppressed. TiFe, TiFe 2 , Ti 5 Cr 8 Fe 16 , and Cu-Ti-Fe phases were found inside the weld and near the interface. The IMCs were separated by Cu matrix and no continuous layered IMCs were found. The brittle fracture characteristics of Ti Fe IMCs and plastic deformation of the Cu matrix was found on the fracture surface in the weld. • Ni-free laser joining of Mo and stainless steel was achieved with Cu Ti filler metal. • The formation of Mo Fe compounds in the weld was significantly suppressed. • The Ti Fe, Ti-Cr-Fe and Cu-Ti-Fe phases were separated by Cu matrix. • No continuous layered intermetallic compounds were found. • Plastic fracture characteristics of Cu matrix was found in the weld. [ABSTRACT FROM AUTHOR]

Herein, the Cu 6 Sn 5 coatings with principal crystal orientations were prepared on the Cu substrate using magnetron sputtering to inhibit the growth of interfacial intermetallic compounds (IMCs) in Sn-0.7Cu/Cu solder joint. The effect of sputtering parameter on the principal crystal orientation of Cu 6 Sn 5 coating was researched firstly, followed by the investigation on the influence of Cu 6 Sn 5 coating principal orientation on the interfacial IMCs growth kinetics. The influence mechanisms were studied using molecular dynamics simulations and first-principles calculations. The results revealed that the increasing sputtering power from 40 W to 60 W and 80 W can not only improve the bonding property between the prepared Cu 6 Sn 5 coating and Cu substrate, but also promote the transformation of the coating principal orientation from (132) to (132)/(22-1) and (132)/(22-1)/(42-2). Moreover, the three prepared Cu 6 Sn 5 coatings can inhibit IMC growth at SC07/Cu solder joint, and the Cu 6 Sn 5 coatings with (132)/(22-1) and (132)/(22-1)/(42-2) principal orientations exhibit more significant inhibitory effects on IMC growth than that with (132) principal orientation. It can be proved in this work that the growth of interfacial IMCs in Sn-0.7Cu/Cu solder joint at aging stage is mainly caused by the diffusion of Cu from Cu substrate toward Cu 6 Sn 5 phase. The difference in the growth behavior of IMCs can be attributed to the fact that when the Cu atoms diffuse across Cu 6 Sn 5 (22-1) and Cu 6 Sn 5 (42-2), the bonding strength between the Cu atom at the saddle point and its surrounding atoms is significantly larger than when diffusing across Cu 6 Sn 5 (132), leading to the smaller diffusion coefficients and a slower interfacial IMCs growth rate. [Display omitted] • The Cu 6 Sn 5 coatings with different principal crystal orientations were prepared. • Cross-scale simulations (MD and DFT) were employed to research the mechanism. • Enhanced sputtering power promotes transformation of the coatings' principal orientations. • IMCs growth is controlled by Cu atom diffusing from Cu substrate toward Cu 6 Sn 5. • Cu 6 Sn 5 (22-1) and Cu 6 Sn 5 (42-2) orientations can inhibit interfacial IMCs growth. [ABSTRACT FROM AUTHOR]

Toward the evolution of integrated optoelectronic circuits, it is vital matter to realize 2D optical waveguide at micro/nanoscale. However, due to the waveguiding principle of the traditional dielectric waveguide, the transverse and longitudinal dimensions cannot be greatly reduced, thus the size of photonic apparatus is far from reaching the size level for the microelectronic device. Therefore, it is difficult to achieve a high‐level hybrid integration of integrated optical path and microelectronic circuit. However, the organic crystals with polygonal structure and hierarchical structure as the medium also can form optical waveguide by confining photons/electrons at the micro/nanoscale along different directions, and these organic microcrystals can be well applied into the ultracompact optoelectronic devices. Herein, the fabrication of organic crystals as the medium of 2D optical waveguide is briefly introduced, as well as the 2D optical waveguide phenomenon existing in these polygonal and hierarchical microcrystals. Moreover, a conclusion is drawn and expectations are expressed for the 2D optical waveguide based on organic microstructure in the near future. [ABSTRACT FROM AUTHOR]

A novel surface honeycomb modification was developed by pre-oxidizing the C f /SiC composite, and the honeycomb modified C f /SiC composite and stainless steel were brazed with AgCuTi filler. Results showed that a honeycomb-like surface with dense pores could be obtained when the C f /SiC composite was air-oxidized at 700°C. During the brazing process, the liquid filler infiltrated into the pores and formed an infiltrated area, which not only significantly increased the bonding area between the reaction layer and the C f /SiC composite, but also effectively hindered the crack propagation due to the nailing/pinning effect. The Finite Element simulation displayed that the infiltrated area transferred the stress concentration away from the reaction layer, dispersed the residual stress and reduced the corresponding stress value. As the result, the maximum shear strength of the joint reached 158MPa, which is multiple times higher than the joint without surface honeycomb modification. [ABSTRACT FROM AUTHOR]

In this study, Ti–Si–C composite coatings were synthesized via plasma spraying of agglomerated powders prepared by a spray drying/precursor pyrolysis technology using Ti, Si, and sucrose powders. The influence of Si content, ranging from 0 wt% to 24 wt%, on the microstructure, mechanical properties, and oxidation resistance of the composite coatings was investigated. Results show that the phase composition of the Ti–Si–C composite coatings changes with the increasing Si content. The coatings without Si addition consist of TiC and Ti 3 O; the coatings with 6–18 wt% Si are composed of TiC, Ti 5 Si 3 , and Ti 3 O; the coatings with Si content of 24 wt% form only TiC and Ti 5 Si 3 phases. As the Si content increases, the hardness of the Ti–Si–C composite coatings increases first and then decreases, depending on the intrinsic hardness of the ceramic phases, the brittleness of Ti 5 Si 3 , and the defects such as pores and cracks. The Ti–Si–C composite coatings have high wear resistance due to the in-situ synthesized high-hardness TiC and Ti 5 Si 3. Owing to the high brittleness of Ti 5 Si 3 , the increasing Si content leads to higher wear volume loss at room temperature, which can be partially improved in high-temperature wear tests. The oxidation resistance of Ti–Si–C composite coatings increases with the increase of Si content, and the higher the oxidation temperature, the more obvious the influence of the Si addition on oxidation resistance. [ABSTRACT FROM AUTHOR]

A truncated cone-shaped stirring pin with threads was designed to enhance friction stir butt welding (FSBW) quality of AZ31B magnesium alloy and Q235 low carbon steel. The effects of welding speed and rotation speed on the microstructure and properties of joints were studied. Microstructure characteristics and element distribution along the Mg/steel interface were analyzed. The results showed that the truncated cone-shaped stirring pin with threads effectively improves the metal flow behavior, especially the fluidity of steel. A steel-strip was formed at the bottom of the Mg side weld nugget during the welding process. The stirring pin effectively improved the interfacial reaction at the Mg/steel dissimilar metal. A thin accumulation layer of the Al was observed along with the interface. Discontinuous oxides of Mg appeared in the interface and were mainly distributed in the upper and bottom interfaces of the joint. As the heat input increased, the metallurgical bonding of the Mg/steel interface became stronger, and the joint strength increased. But when the heat input increased to a certain level, the oxidation of the Mg/steel interface became serious. The aggregation of MgO in the Mg/steel interface led to cracks, which decreased the joint strength. When the welding speed was 75 mm/min and the rotation speed was 850 rpm, the highest tensile strength of the joint was 189.4 MPa, which is 75.8 % of magnesium alloy. The joint fractured in the Mg side near the Mg/steel interface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Molecular dynamics and First-principle calculations were both employed. • Transformation of generated IMCs types on wetting interface was researched. • Bonding strength of droplet/IMC interface shows negative correlation with wettability. Wetting behavior and mechanism of melting Al on Ni-infiltrated steel were investigated using the cross-scale simulations. The molecular dynamics calculations were employed firstly to intuitively exhibit the influence of amount of nickel infiltration (on the surface of steel substrate) on wettability of Al droplet. The micro-mechanisms affecting wettability, such as the bonding characteristic and charge distribution on wetting interface, were researched using the first-principles calculations. The results indicate that, the chemical reactions occur on Al droplets/Ni-infiltrated steels wetting interfaces. With the increasing amount of Ni infiltration, the main interfacial intermetallic compound (IMC) transforms from Fe 2 Al 5 to NiAl and finally to Ni 3 Al. Although the atomic bonds on Al/Fe 2 Al 5 , Al/NiAl, and Al/Ni 3 Al interfaces all show both ionic and covalent characteristic, the work of adhesion for the three Al/IMC interfaces follows the order of Al/Fe 2 Al 5 > Al/NiAl > Al/Ni 3 Al. This phenomenon indicates that the interfacial bonding strength between Al droplet and the generated IMC decreases gradually with the increasing amount of Ni infiltration, and leading to the improving wettability because the wettability is negatively correlated with the Al/IMC bonding strength on wetting interface. [ABSTRACT FROM AUTHOR]

The influence of interfacial configuration on the bonding property and wettability between CuNiTi active filler metal and AlN ceramic was investigated using first-principles calculations within the framework of density functional theory. The results indicate that different AlN ceramic crystal planes lead to various interfacial properties in the CuNiTi active filler metal/AlN ceramic system. For the AlN non-polar crystal plane, such as AlN (100) and AlN (110), the chemical reaction with the CuNiTi filler metal increases the interfacial bonding strength because the ionic bonding at the CuNi/TiN interface is greater than that at the CuNi/AlN interface. For the AlN polar crystal plane, such as AlN (111), the chemical reaction decreases the interfacial bonding strength because the ionic bonding and covalent bonding at the CuNi/TiN interface are both weaker than that at the CuNi/AlN interface. However, the interfacial bonding strength of the CuNi/TiN (111) interface is still much larger than those of the CuNi/TiN (100) and CuNi/TiN (110) interfaces, indicating CuNiTi filler metal has better interfacial bonding property with the AlN polar crystal plane. Moreover, for the AlN (100) and AlN (110) crystal planes, the chemical reaction leads to an increase in interfacial energy, indicating that non-polar crystal planes are not conducive to the wetting and spreading of CuNiTi filler metal, while for the AlN (111) crystal plane, the chemical reaction leads to a decrease in interfacial energy, indicating that CuNiTi filler metal has good wettability with the AlN polar crystal plane. [ABSTRACT FROM AUTHOR]

To investigate the influence of Ni coating layer on the interfacial reaction of Al/steel dissimilar metal brazing, a high-frequency brazing method of Al alloy and steel with/without a Ni coating layer were designed. The steel side interfacial microstructure of the Al/bare steel joint consisted of Fe (Al,Si) 3 , Al 7.2 Fe 1.8 Si. After the preparation of the Ni coating layer on the stainless steel, the interfacial microstructure consisted of Al 3 Ni, Al 3 Ni 2 , and residual Ni coating layer. An ultra-thin Al 3 Ni 2 reaction layer was observed in Al/Ni-coated steel joint by transmission electron microscopy (TEM). With increasing reaction time, the Ni coating layer completely dissolved into liquid filler metal. Interfacial structure transformed into Fe(Al,Si) 3 /Al 7.2 Fe 1.8 Si, which was the same as that of the Al/bare steel joint. The shear strength of the joint with the Ni-coated layer increased first and then decreased with increasing brazing time, which was influenced by the dissolution level of Ni coating layer. The maximum shear strength exceeded 20.3% that of the joint without Ni coating layer. The element diffusion phenomenon in the field of the solid/liquid interface and the dissolution behavior of the Ni coating layer were analyzed by the thermodynamics method. A model of Ni dissolution kinetics was established to optimize the thickness of the Ni coating layer and the processing parameters of the brazing. The effect mechanism of Ni coating layer on the interfacial reaction of the Al/steel dissimilar metal brazing was clarified. • An ultra-thin Al 3 Ni 2 reaction layer was observed in Al/Ni-coated steel joint by TEM technology. • Microstructure and properties of Al/Ni coated joint were compared with that of Al/bare steel joint. • The Si aggregation behavior was clarified by calculation of chemical potential. • Clarify the effect mechanism of Ni coating layer on the Al/steel brazing. [ABSTRACT FROM AUTHOR]

The interfacial reaction between solid Ni and liquid Al, such as dissolution behaviors of solid Ni and formation mechanisms of intermetallic compounds, are not thoroughly clarified yet, especially under the conditions of short holding time and high reaction temperature. In this study, a hot-dip method was designed to investigate the isothermal interfacial reaction mechanism of solid Ni and liquid Al at temperature of 700 °C, 800 °C and 900 °C for 0–40 s. The dissolution behavior of solid Ni in liquid Al was analyzed. The dissolution rate constant, K Ni , and dissolution activation energy, Ea , were calculated. The microstructure analysis with scanning electron microscope (SEM) and transmission electron microscopy (TEM) revealed that the dissolved thickness of solid Ni in pure liquid Al has linear relationship with the reaction time. The microstructure of the reaction interface consisted of Ni, Ni based solid solution, Al 3 Ni 2 layer, adhered Al 3 Ni layer, free Al 3 Ni, Al 3 Ni + Al eutectic structure and Al. Ni based solid solution structure firstly formed at the holding stage. Nano-scale Al 3 Ni 2 and irregular adhered Al 3 Ni appeared at the interface during fast cooling stage. • Investigate the interfacial reaction between solid Ni and liquid Al for short times (0–40 s) • Interfacial microstructure was observed by TEM. The sample was prepared by FIB. • Clarify the formation mechanism of microstructure • Analysis the dissolution kinetics of solid Ni in comparison to previously published conclusions [ABSTRACT FROM AUTHOR]

In order to propel the application of the developed CuNi-Xwt%Ti active filler metal in AlN brazing and get the universal reactive wetting mechanism between liquid metal and solid ceramic, the reactive wetting behavior and mechanism of AlN ceramic by CuNi-Xwt%Ti active filler metal were investigated. The results indicate that, with the increasing Ti content, surface tension for liquid CuNi-Xwt%Ti filler metal increases at low-temperature interval, but very similar at high-temperature interval, which influence the wetting behavior on AlN ceramic obviously. CuNi/AlN is the typical non-reactive wetting system, the wetting process including rapid wetting stage and stable stage. The wettability is depended on surface tension of the liquid CuNi filler metal completely. However, the wetting process of CuNi-8wt.%Ti/AlN and CuNi-16 wt%Ti/AlN reactive wetting system is composed by three stages, which are rapid wetting stage decided by surface tension, slow wetting stage caused by interfacial reaction and stable stage. For CuNi-8wt.%Ti/AlN and CuNi-16 wt%Ti/AlN reactive wetting system, although the surface tension of liquid filler metal is the only factor to influence the instant wetting angle θ 0 at rapid wetting stage, the reduced free energy caused by interfacial reaction at slow wetting stage plays the decisive role in influencing the final wettability. [ABSTRACT FROM AUTHOR]

Taking advantages of reaction composite brazing, transient liquid phase bonding (TLP) and partial transient liquid phase bonding (PTLP), a novel process with the characteristics of low-temperature bonding and high-temperature resisting was developed for joining C f /SiC composite to GH3044 alloy by using (Cu-Ti) + C + Ni mixed powder filler. Under the bonding temperature (980 °C), the reaction between the liquid Cu-Ti alloy and C particles (reaction composite mechanism), composition homogenizations between the joining layer and Ni particles (PTLP mechanism) as well as Ni-based substrate (TLP mechanism) occurred to complete the transformation (Cu,Ti) l + C s + Ni s → TiC s + (Cu,Ni) s. Thereby, a joint with high-temperature resistance and excellent mechanical properties was obtained in relatively short holding time. The melting-point of the joint (1050 °C) was obviously higher than that of Cu-Ti alloy (898 °C) in the filler. The bonded joints exhibited shear strengths of 229, 225 and 104 MPa at room temperature, 600 °C and 1000 °C, respectively. [ABSTRACT FROM AUTHOR]

• A novel high frequency electric cooperated arc welding method was developed. • Thermal transfer mode of conduction in traditional arc welding was changed. • Welding speed was raised to 3–4 times that of traditional arc welding. • Heat input needed for the welding process was reduced by 40%. • The welded joint possessed the equal strength of the base metal. High efficiency and low heat input are the pursuit of modern welding. In this paper, an innovative high frequency electric cooperated arc welding (HFAW) was developed. The process and joint characteristics of the HFAW were compared with that of traditional arc welding (TAW). In the HFAW, a part of welding heat is generated all over the surface of weld side wall (WSW) directly and rapidly due to the skin effect and proximity effect of high frequency current. The limitation of heat conduction on the TAW was broken through. Benefited from the ultra-speed welding thermal process, the HFAW reaches 3–4 times the welding speed of the TAW, while the heat input needed in the HFAW was only about 60% that in the TAW. Meanwhile, the HFAW joint presented sound weld formation, complete penetration and finer microstructure, which made the joint possess an equal tensile strength with the base metal. [ABSTRACT FROM AUTHOR]

93WNiFe alloy and 30CrMnSiA steel was diffusion bonded successfully with NiFeW solid solution (NiFeWss) interlayer prepared on the surface of the former by using in-situ reduction technology. The microstructure, property, and metallurgy mechanism of the joint was investigated by experiments and molecular dynamic simulations. The results indicate that, the microstructure of the joint using NiFeW SS interlayer with ideal purity (100%) and suitable average thickness (∼100 μm) is W/ (NiFeW SS matrix + tiny W particle) diffusion layer /steel, without any interfacial intermetallic compound. The thermal expansion coefficient of (NiFeW SS matrix + tiny particle W) diffusion layer is between that of W substrate and steel substrate, which is beneficial to release the residual thermal stress. At the optimized technology parameters, which are bonding pressure of 50 MPa, bonding temperature of 1020 °C and holding time of 60 min, the tensile strength of the joint reaches 289 MPa. The formation mechanism of diffusion layer can be elaborated that, at the bonding temperature, although W particles in W substrate do not provide any element into NiFeWss interlayer, the mutual diffusion behaviors between steel substrate and NiFeWss interlayer, especially element Ni (diffusion coefficient of 5.29 × 10−9 m2/s) and element Fe (diffusion coefficient of 2.75 × 10−9 m2/s), are significantly. The mutual diffusion phenomenon results in the composition deviation of interlayer (diffusion layer), which exceeds the solid solubility of element W in NiFeWss at room temperature. Therefore, as temperature decreases, the excessive element W will be precipitated as tiny W particles, leading to the formation of (NiFeW SS matrix + tiny particle W) diffusion layer. • Interlayer for W/steel diffusion bonding was prepared by an in-situ reduction technology. • The multiphase composite diffusion layer was obtained in W/steel diffusing bonding joint. • Avoidance of interfacial IMC and release of residual thermal stress were achieved. [ABSTRACT FROM AUTHOR]

In this study, a novel Ag–Ti reactive composite brazing technology was employed to join carbon fiber reinforced carbon matrix composite (C/C) to Nickel-based superalloy GH3044. The microstructural evolution mechanism and the effects of process parameters on the microstructures and shear strength of the brazed joints were investigated systematically. The results showed that, during the brazing holding stage, Ti (α-Ti) in the liquid phase would convert to β-Ti (above 1020°C) or react with Ag formed AgTi (below 1020°C). Solid phase β-Ti or AgTi inhibited the loss of the molten filler material, thus forming a thicker interlayer, which was beneficial to relieve the residual stress of the joints. After brazing, an Ag matrix composite interlayer reinforced by in situ synthesized phases and a few residual Ti particles could be obtained. Notably, the reinforcing phases were various with different brazing parameters. Under weaker parameters (lower Ti content, lower temperature and shorter holding time), the reinforcing phases were mainly in situ synthesized AgTi phase and residual Ti particles, with which the Ag matrix composite interlayer had good plasticity and low coefficient of thermal expansion. As a result, the residual stress of the joints was further effectively relieved. Under stronger parameters, the reinforcing phases were mainly brittle phases Ti 2 Ni and Cr 1.93 Ti 1.07 , which increased the brittleness of the composite interlayer. The maximum shear strength of the joints reached 45.8 MPa brazed at 1020°C for 30 min using Ag–20Ti (Wt.%). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The most representative Ni/W interfaces were selected. • Chemical bonds formed at Ni/W interfaces show covalent character and ionic character. • Sustainable imposed strain of Ni (1 1 1)/W (1 1 1) interface is the largest. • Layer 2′-1′ in Ni slab but the interface is the fracture point for Ni (1 1 1)/W (1 1 1) interface. Abstract In order to optimize the microstructure and improve the performance of Steel/Ni/W hot isostatic pressure (HIP) diffusion bonding joint, the interfacial structure, electron orbital hybridization, charge distribution, bonding characteristic and fracture process of Ni/W interface were investigated using first-principles density functional theory. The results indicate that, besides Ni (1 0 0)/W (1 0 0) interface, Ni (1 1 0)/W (1 1 0) interface and Ni (1 1 1)/W (1 1 1) interface, Bramfitt's lattice mismatches of the others Ni/W interfaces are all larger than 6%. Therefore, only those three interfaces can be considered as the typical Ni/W interfaces. For Ni (1 0 0) surface, W (1 0 0) surface, Ni (1 1 0) surface, W (1 1 0) surface, Ni (1 1 1) surface and W (1 1 1) surface, when the number of atomic layers are 5, 7, 7, 5, 5 and 5, their surface energies convergence to 2.24 J/m2, 4.03 J/m2, 2.18 J/m2, 3.23 J/m2, 1.92 J/m2 and 3.56 J/m2. At the three typical Ni/W interfaces, the chemical bonds between Ni slabs and W slabs are the typical metallic ones, but also show a certain degree of covalent characteristics and ionic characteristics. Moreover, the metallic bonding strength of Ni (1 1 1)/W (1 1 1) interface is larger than that of Ni (1 0 0)/W (1 0 0) interface and Ni (1 1 0)/W (1 1 0) interface, so are the covalent characteristics and ionic characteristics. The tensile fracture process shows that for Ni (1 0 0)/W (1 0 0) interface and Ni (1 1 0)/W (1 1 0) interface, when the large external strain is imposed, the inner strain of the interfacial structure is not equivalent but concentrates at layer 1′-1, which indicates that the layer 1′-1 (interface itself) is the weakness. However, for Ni (1 1 1)/W (1 1 1) interface, the concentrated strain is located at layer 2′-1′, which illustrates that the weakness is not the interface anymore but in Ni slab. Moreover, the sustainable imposed strain of Ni (1 1 1)/W (1 1 1) interface is ∼30%, much higher than that of Ni (1 0 0)/W (1 0 0) interface and Ni (1 1 0)/W (1 1 0) interface, which are ∼15% and ∼12%, respectively. [ABSTRACT FROM AUTHOR]