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Age-hardenable 2000- and 7000-series aluminium alloys share the ability to achieve outstanding combinations of high specific strength and fracture toughness without including expensive alloying elements such as scandium. Using laser surface melting (LSM), we investigate the suitability of two commercial, high-strength aluminium alloys (ultimate tensile strength ≥ 600 MPa) for laser powder bed fusion (L-PBF). It is revealed that solidification cracks form in both, the third-generation Al-Cu-Li alloy 2065 and the high-Zn containing alloy 7034, with the latter having a lower crack density. Through a combination of microstructural characterisation by SEM, EDS, and EBSD, residual stress analysis and quantitative hot cracking criteria, we deduce that alloy 2065 shows greater potential for L-PBF application despite its slightly higher crack density after LSM. Through laser surface alloying, the composition of alloy 2065 was systematically varied in terms of titanium and copper content to improve its cracking resistance. It is found that the formation of solidification cracks is suppressed by the addition of 2 – 4 wt% Ti, whereas the introduction of copper has little effect. Our study suggests that Ti-modified 2065 is an attractive alloy for L-PBF. It could potentially join the existing high-strength aluminium feedstock materials available for L-PBF. [Display omitted] [ABSTRACT FROM AUTHOR]

CaO-Al 2 O 3 -SiO 2 (CAS) glass ceramics were designed and prepared using a melt-quench approach. The coefficient of the thermal expansion (CTE) of the synthesized CAS (4.12 × 10−6 K−1) matched perfectly with that of the SiC ceramic (4.01 × 10−6 K−1). Thermal analysis of the CAS was conducted. Then the joining of the SiC ceramics by the CAS glass ceramics under various process parameters were conducted. The bonding temperature affects the fluidity of the CAS glass and the oxidation of the SiC substrate. The holding duration decides the infiltration of the CAS glass into the SiC substrate. The optimal bonding parameter is 1400 ℃/10 min and the corresponding highest shear strength of the SiC/CAS/SiC bonded joints in average was 56 MPa. Fracture observation was also conducted to help analyze the relationship between the interfacial microstructure and the joint strength. Finally, the formation mechanism of the SiC/CAS/SiC bonded joints was proposed. [ABSTRACT FROM AUTHOR]

We investigated the field emission properties and resistivity of polymer-based carbon films prepared from poly ethyl-co-phenyl carbyne polymer precursors after treatment at different temperatures. As the heat-treatment temperature increased from 40 to 1200 °C, the emission threshold field decreased from 12.4 to 2.1 V/μm, the emission current density increased from 0.1 to 6.1 mA/cm2, and the film resistivity decreased from 108 to 102 Ω cm. The structural changes of the polymer films during the heat-treatment process were analyzed by Raman spectroscopy and atomic force microscopy. Raman analysis of these polymer-based carbon films suggests that the hydrogen content decreased while the sp2 carbon phase increased as the heat-treatment temperature increased. The dependence of the field emission properties of the polymer-based carbon films on the film structures (such as sp3, sp2 phases), film surface morphology and film resistivity is discussed. The enhancement of field emission from polymer-based carbon films was related to the increase of sp2/sp3 ratio, film conductivity, and surface roughness with the heat-treatment temperature. [ABSTRACT FROM AUTHOR]

Abstract To address the thermal stress issue in the brazed SiO 2f /SiO 2 -Invar joints, a novel nano-TiO 2p (p: particle) modified braze filler was developed. Wetting of the SiO 2f /SiO 2 composite by AgCuTi-based composite braze filler with different TiO 2p contents were conducted first and a TiO 2p content lower than 5 wt% was fixed. Then the microstructure evolution and mechanical performance of the SiO 2f /SiO 2 -Invar joints brazed with different TiO 2p additions and different brazing parameters were discussed. The highest shear strength of 30 ± 8 MPa was obtained at 910 °C/10 min. After using the TiO 2p modified braze filler, the fracture probability of the SiO 2f /SiO 2 -Invar joints dropped down by 75% (Taking 22 MPa as an example). Finally, a FEM was employed to get an in-depth understanding of the stress relief effects when using a TiO 2p modified braze filler. Results show that the compressive stress on the SiO 2f /SiO 2 side dropped down by 30% after using a 2 wt% TiO 2p modified braze filler. The in-situ formed Cu x Ti 6-x O (x = 2, 3) phases played a key role in relieving the residual stress of the brazed joints. The development of the novel TiO 2p modified braze filler was particularly suitable for the joining of the oxide ceramics and oxides-based composites. [ABSTRACT FROM AUTHOR]

Abstract For active brazing, excessive formation of brittle intermetallics in the brazed seam is always a big issue, which has an adverse effect on the joint property. Herein, an innovative vertical few-layer graphene (VFG) buffer layer was directly grown on the Invar surface prior to brazing. SiO 2 -BN ceramic and the Invar alloy with and without the VFG were first brazed using a Ag-Cu-Ti braze alloy. Interfacial microstructure and fracture morphologies of the brazed joints were then put into comparison. Results show that there is a 20% increase in shear strength after the VFG modification. To further discuss the effect of the interfacial microstructure variation on the joint property, Invar alloy was self-brazed. The fracture path and the tensile-shear strength of the Invar/Invar joints were discussed. Finally, the interaction between the VFG and Ti was characterized and the controlling mechanism of the intermetallic compounds formation by the VFG was proposed. This novel surface modification approach reported in this paper was promising particularly for the active brazing associated with the brittle IMCs formation issue. [ABSTRACT FROM AUTHOR]

For the active brazing of ceramic/metal couples, formation of brittle intermetallics in the brazed seam is often a big issue that needs to be addressed. Herein, a novel vertical few-layer graphene (VFG) modified Cu-23Ti braze filler was developed to join the SiO 2f /SiO 2 composite and the Invar alloy. Microstructures of the wetting interfaces and the SiO 2f /SiO 2 -Cu23Ti-Invar brazed joints with and without the VFG modification were put into comparison. Results show that the formation of intermetallics in the brazed seam are greatly suppressed and the joint strength improves by 2 times after using a VFG-modified Cu-23Ti braze filler. Typical microstructure of the SiO 2f /SiO 2 -Invar joint brazed using a VFG-modified Cu-23Ti braze filler was characterized and the joint formation mechanism was proposed finally. [ABSTRACT FROM AUTHOR]

The original article can be found online at https://doi.org/10.1007/s00339-016-0605-7. 3X-ray diffraction patterns of AZ61 fabricated by ES process with different die channel angles The authors would like to apologise for any inconvenience caused. [Extracted from the article]

An AgCu-4.5 wt.%Ti/W/AgCu-1 wt.%Ti composite interlayer was designed to braze the Invar-SiO 2f /SiO 2 joints. Ti contents in the interlayer between the tungsten foil and the Invar alloy was optimized. The effects of the tungsten-foil thickness on the microstructure, elemental distribution and mechanical properties of the brazed joints were investigated. Compared with a single AgCu-4.5 wt.%Ti interlayer, a sufficient metallurgical reaction happened on the SiO 2f /SiO 2 composite side and the formation of Fe 2 Ti, Ni 3 Ti compounds which are detrimental to the joint properties, was greatly inhibited by using a low-expansion composite interlayer (LECI). The tungsten interlayer can reduce the CTE (coefficient of thermal expansion) mismatch in the Invar-SiO 2f /SiO 2 joint. The highest shear strength of joints brazed with an LECI was 33 MPa, which was 1.75 times higher than the joints brazed with a single AgCu-4.5 wt.%Ti interlayer. [ABSTRACT FROM AUTHOR]

The effects of electropulsing on the machinability and microstructure of the machined surface of GH4169 superalloy are investigated in the present work. The results indicate that the machinability and the surface quality of GH4169 superalloy achieve evident improvements during the electropulsing-assisted turning process (EP-TP) at appropriate electropulsing parameters compared with the traditional dry turning process (TD-TP). In EP-TP at the frequency of 400 Hz and the root-mean-square (RMS) current density of 0.64 A mm-2, the main cutting force, the axial surface roughness, and the surface microhardness are reduced dramatically. In addition, the quality of machined surface and the ability of plastic deformation are also facilitated significantly under the effects of electropulsing. For GH4169 superalloy, the enhanced ability of the plastic deformation and the promoted mobility of dislocations in the cutting layer under the influence of the coupling of thermal and athermal effects of the exerted electropulsing are likely the primary reasons for the observed phenomena. [ABSTRACT FROM AUTHOR]

The effect of extrusion combined with shear (ES) on the microstructure and mechanical properties of magnesium alloy AZ31 is studied. The additional die providing shear deformation of the extruded bars (two successive turns of the calibrating channel to equal opposite angles) provides refinement of grains. Growth of the deformation temperature causes grain growth. The intensity of the x-ray reflection from basal plane (0002) after the ES increases. After the deformation at 420°C fracture mainly develops by the transgrain mechanism. After the deformation at 450°C the maximum hardness corresponds to the largest grain size in the central part of the bar, and the fracture is chiefly determined by twinning. [ABSTRACT FROM AUTHOR]

In many industrial applications, large-sized SiC components are increasingly desired through a conventional and pressureless brazing method. In present study, Ni-Si-Ti powder mixtures containing 0~10 wt.% Ti were used to braze SiC ceramics. Differential thermal analysis (DTA) and wetting tests were carried out to determine the appropriate joining temperature to be at 1450 °C. Microstructure, phase constituents, and mechanical strength of the prepared SiC joints were characterized. For a brazing composition without Ti addition, the interlayer primarily consists of NiSi and Ni3Si2 phases. With the addition of Ti, Ni49Ti14Si37 phase is newly formed within the interlayer besides the Ni-Si compounds. The bending strengths of SiC joints locate in 66~75 MPa as brazed at present conditions and the specimens generally fracture from the interface between alloy interlayer and SiC substrate. [ABSTRACT FROM AUTHOR]

Electron Backscatter Diffraction technique is used to characterize the microstructure of 316L steel generated by Surface Mechanical Attrition Treatment (SMAT) before and after low cycle fatigue tests. A grain size gradient is generated from the top surface to the interior of the samples after SMAT so that three main regions can be distinguished below the treated surface: (i) the ultra-fine grain area within 5 μm under the top surface with preferably oriented grains, (ii) the intermediate area where the original grains are partially transformed, and (iii) the edge periphery area where the original grains are just mechanically deformed with the presence of plastic slips. Fatigue tests show that cyclic loading does not change the grain orientation spread and does not activate any plastic slip in the ultra-fine grain top surface area induced by SMAT. On the opposite, in the plastically SMAT affected region including the intermediate area and the edge periphery area, new slip systems are activated by low cycle fatigue while the grain orientation spread is increased. These results represent a first very interesting step towards the characterization and understanding of mechanical mechanisms involved during the fatigue of a grain size gradient material. [ABSTRACT FROM AUTHOR]

Transient liquid bonding (TLP) of IC10 single crystal with GH3039 alloy was carried out using BNi2 interlayer. Microstructure evolution and mechanical properties of the joints bonded at 1050-1200 °C for 2 h were investigated. The precipitates in the DZ on the GH3039 side gradually decreased and disappeared with the increase of the bonding temperature. The formation mechanism of the TLP joint was proposed and the asymmetry of the bonding was discussed. Tensile strength and microhardness tests were conducted to investigate the mechanical properties of the joints. The layer of borides with high hardness in the joint bonded at 1150 °C significantly reduced the room-temperature tensile strength but had little effect on the high-temperature tensile strength of the joint. The layer of borides became the preferential position to crack during both room-temperature and high-temperature tensile tests. The joints with dispersive precipitates had the highest room-temperature tensile strength and the homogenized joints showed the best ductility. [ABSTRACT FROM AUTHOR]

Transient liquid bonding (TLP) of IC10 single crystal with GH3039 alloy was carried out using BNi2 interlayer. Microstructure evolution and mechanical properties of the joints bonded at 1050–1200 °C for 2 h were investigated. The precipitates in the DZ on the GH3039 side gradually decreased and disappeared with the increase of the bonding temperature. The formation mechanism of the TLP joint was proposed and the asymmetry of the bonding was discussed. Tensile strength and microhardness tests were conducted to investigate the mechanical properties of the joints. The layer of borides with high hardness in the joint bonded at 1150 °C significantly reduced the room-temperature tensile strength but had little effect on the high-temperature tensile strength of the joint. The layer of borides became the preferential position to crack during both room-temperature and high-temperature tensile tests. The joints with dispersive precipitates had the highest room-temperature tensile strength and the homogenized joints showed the best ductility. [ABSTRACT FROM AUTHOR]

Due to the poor wettability of the AgCuTi alloy on the SiO2f/SiO2 composite, direct brazing of the composite with an Invar alloy could hardly achieve a reliable joint. To overcome that, the SiO2f/SiO2 composite was decorated with few-layer graphene (FLG) by a plasma enhanced chemical vapor deposition (PECVD) method. Sessile drop experiments indicate that the contact angle dropped from 123.8° to 50.7° after FLG was grown on the surface of the SiO2f/SiO2 composite. Afterwards, the effects of brazing temperature and Ti contents on the microstructure evolution and mechanical properties of joints (Invar/SiO2f-SiO2 modified with FLG) were investigated. The typical interface structure of the joint is SiO2f- SiO2/Ti5Si3 + TiO2 + CuxTi6 - xO(x = 2,3)/Ag(s,s) + Cu(s,s) + Cu-Ti blocks/wave-like Fe2Ti + Ni3Ti/Ag(s,s) + Cu(s,s) + Fe2Ti + Ni3Ti blocks/Invar. As the brazing temperature and Ti contents increase, the reaction layer on the SiO2f/SiO2 side becomes thicker and cracks gradually propagate. Meanwhile, a few dispersive Fe2Ti + Ni3Ti phases change into large-area wave-like compounds and more Cu-Ti compounds form with the increase of the Ti content. The microstructure evolution significantly affects the shear strength of the brazed joints. The highest shear strength is 26 MPa brazed at 860 °C for 10 min with 4.5 wt.% Ti content. [ABSTRACT FROM AUTHOR]

The influence of homogenisation annealing process on microstrucure of 7085 Al alloy has been investigated by optical microscopy(OM), scanning electron microscopy combined with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction(XRD), and differential scanning calorimetry (DSC). The results show a large amount of skeletal Mg(Zn, Al, Cu)2 phase and AlZnMgCu phase distributed as eutectic microstructure on crystal boundaries, and some impurity phase of triangle or square Al18Mg3Cr2 in the interior of grain in as-cast 7085Al alloys. In combination with DSC and OM observation, the temperature of homogenisation annealing is determined lower than 473°C. With increasing temperature of homogenising annealing, the woven crystal microstructure on the grain boundary and part lager block second phase in interior of grain decreases, and grain boundary turns to be discontinuous. 7085Al alloys are treated by homogenising annealing of 470°C/24 h, grain boundary turns to be discontinuous, uniform and fine precipitation phase arises, and woven eutectic microstructure and lager block second phase disappear. The optimised homogenising annealing is 470°C/24 h in the study. [ABSTRACT FROM AUTHOR]

The AlFeCoNiCrSn high-entropy alloys (HEAs) are fabricated. The microstructure and mechanical properties of the alloys are investigated. The results show that alloying elemental content plays a significant role in the microstructure and properties of the alloys. When Sn content is <0.05, the AlFeCoNiCrSn HEAs consist of only BCC solid solution and possess high strength and good plasticity. While Sn content is above 0.05, the CoSn intermetallic compounds form, formation of intermetallic compounds decreases the plasticity of alloy. The maximum strength and stain values of alloys can reach 2,180 MPa and 18.1%, respectively. [ABSTRACT FROM AUTHOR]

The effects of pressure treatment at room temperature on the microstructure and corrosion resistance in seawater solution of the as spun RE65Co25Al10 (RE = Ce, La, Pr, Sm and Gd) metallic glass ribbons have been investigated using X-ray diffraction, differential scanning calorimetry, scanning electron microscopy and electrochemical workstation. The results indicate that the pressure treatment causes the changes of microstructure, which results in the variation of the glass transition temperature and supercooled liquid region of the RE65Co25Al10 metallic glass. The RE65Co25Al10 metallic glass treated by pressure in 16 kN exhibits low self-corrosion current density and distinct passive region, indicating the higher seawater corrosion resistance. However, the corrosion resistance of the RE65Co25Al10 metallic glass becomes poor with increasing pressure to 30 kN. The discussion of the corrosion mechanism has been made based upon the structural relaxation and bonding force of the matrix elements and oxygen during the electrochemical corrosion process. [ABSTRACT FROM AUTHOR]

Highlights: [•] M50NiL steel is nitrocarburized with and without rare earth (RE) addition. [•] RE addition can increase the surface hardness and layer thickness. [•] RE can increase C, N contents and proportion of iron nitrides in treated layers. [•] Plasma nitrocarburizing can significantly improve the wear resistance of M50NiL steel. [•] RE addition could further improve the wear properties of the treated layers. [ABSTRACT FROM AUTHOR]

A log-pile photonic crystal of CdS nanoparticles–polymer nanocomposites was successfully fabricated by a novel method combining the two-photon polymerization technique and in situ synthesis of CdS nanoparticles in a polymer matrix. The photonic band gap of the three-dimensional (3D) log-pile photonic crystal is confirmed and becomes more effective for CdS nanoparticles–polymer nanocomposites than polymer doped with Cd2+ ions, because the nanocomposites possess a higher refractive index than the polymer. The proposed concept in the new fabrication method for a 3D microstructure of polymer nanocomposites should be of critical importance in providing a general methodology for functionalization of materials via functional nanocomposites used in the field of laser microstructure fabrication. [ABSTRACT FROM AUTHOR]

Duplex stainless steels are characterized by balanced ferrite/austenite microstructures and are well known for their superior corrosion resistance and higher strength compared with the common austenitic stainless steels. One major concern, however, is that welding might degrade the corrosion resistance by producing unbalanced phase content, detrimental precipitates, and possible embrittlement of the weldment. In this paper, a dual-torch arc welding technique (plasma torch followed by a gas tungsten arc (GTA) torch) was proposed. Effects of the dual-torch technique on the microstructural changes and corrosion properties were investigated. The preliminary study indicated that a correlation between the welding parameters and the microstructural changes and corrosion resistance existed. It was found that the corrosion rate increases with increasing torch pitch and/or decreasing GTA welding current. By adjusting the distance between the torches, modification of weld microstructure may be realized. Although further studies are required to fine-tune the technique, the present study demonstrated the potential of using dual torch technique to improve weldability of duplex stainless steels. [Copyright &y& Elsevier]

Cobalt films were deposited on special porous silicon substrate composing of nanosized noodle-like channels with large length-to-axis ratio. Modulation effects due to the substrate on microstructure, domain structures, and magnetic properties of the Co films were studied. Magnetic images and hysteresis loops indicate that a large uniaxial in-plane shape anisotropy is induced in the magnetic cobalt films. Accordingly, the magnetization of the magnetic cobalt films lies in the film plane, along the noodle direction. The coercivity of the cobalt films is enhanced as compared to reference cobalt film that was grown on a flat silicon substrate. [ABSTRACT FROM AUTHOR]

Size self-scaling effect in stacked InAs/In0.52Al0.48As nanowires on InP substrates is revealed, i.e., the base width and height of the InAs nanowires have clear proportional dependence on thickness of the InAlAs spacer layer used in different samples. The photoluminescence wavelength from different samples, which varies between 1.3 and 1.9 μm, is also found closely correlated to the size self-scaling effect. This phenomenon can be well explained in the context of formation mechanism and growth features of the InAs/InAlAs nanowire arrays. The finding illustrates a degree of freedom to control the structural and optical properties of strained self-organized nanostructures. [ABSTRACT FROM AUTHOR]

Ceramic/metal interpenetrating network structure has been proved to have a significant effect on decreasing the coefficient of thermal expansion (CTE) of the metal matrix. In our study, a AgCuTi/SiC interpenetrating network structural composite (ASINC) was fabricated through a melt infiltration method. During the infiltration process, the AgCuTi filler melted and infiltrated into a porous SiC ceramic. Wetting behavior of the AgCuTi on the porous SiC ceramic was studied. Microstructure of the ASINC was characterized. The synthesized ASINC was fabricated as an interlayer to prepare a ZrB 2 –SiC–C ceramic/AgCuTi/ASINC/AgCuTi/GH99 brazed joint. Typical microstructure of the joint brazed at 860 °C for 10 min was investigated. The effect of holding time on the microstructure and the room-temperature shear strength of the brazed joints was studied. The maximum shear strength increased by 161% compared with the case brazed with a single AgCuTi interlayer. Microstructure evolution and mechanical strengthening mechanisms of the brazed joints were discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract Graphene nanosheets (GNSs) had been considered as the potential reinforcements of the composites. In this study, sponge-like graphene was used as a reinforcement to enhance the dispersity of GNSs in the metal matrix. AgCuTi alloy was melted and infiltrated into the sponge-like graphene, which led to the reaction between the GNSs and the AgCuTi alloy. The microstructure on the interface of the GNSs and AgCuTi alloy was characterized. The GNSs reinforced AgCuTi based composite was utilized as an interlayer to braze graphite and Cu, and the dispersity of the GNSs in the brazing seam was discussed. Comparing with the pure AgCuTi interlayer, the shear strength of the graphite and Cu joint was increased by 75% when the GNSs reinforced AgCuTi based composite interlayer was used. Highlights • GNSs reinforced AgCuTi composite was prepared by a melt infiltration method. • The GNSs in the composite were interconnected and free of any agglomeration. • Graphite and Cu were successfully brazed with the addition of the GNSs. • The shear strength was improved by 75% when the interconnected GNSs were added. [ABSTRACT FROM AUTHOR]

In this study, transparent alumina and TiAl alloy were successfully brazed at 860°C-940 °C using Ag-21Cu-4.5Ti (wt%) filler metal. The microstructure and mechanical properties of the joints were investigated. SEM and TEM analysis showed the typical interfacial microstructure of the joints brazed at 900 °C for 5min was TiAl/β-Ti + AlCuTi/AlCu 2 Ti + AlCuTi/AlCu 2 Ti + Ag(s,s) + Cu(s,s)/(Cu,Al) 3 Ti 3 O/transparent alumina. The effects of brazing temperature and holding time on the microstructure and mechanical properties of TiAl/transparent alumina joint were studied. In addition, the effects of the dissolution and diffusion of TiAl on the microstructural evolution of the brazing seam were discussed. Shear strength analysis reveals that the shear strength of the joint increases at first and then decreases when brazing temperature rises. The maximum shear strength is 49 MPa when the joint is brazed at 900 °C for 5 min. [ABSTRACT FROM AUTHOR]

Al-Ti-Zr ternary system with different compositions (Al 40, 41, 43, 50 at.%) was synthesized by in-situ reaction of ZrH 2 , TiH 2 and Al powders through vacuum hot pressing at 1400 °C for 0.5 h under 40.8 MPa. The microstructure, micro hardness, fracture toughness, and flexural strength of Al-Ti-Zr alloys were investigated. AlTi 2 + TiAl and Zr(Ti)Al + Al 3 (Ti, Zr) 5 new lamellar structures were found in the samples. Micro hardness increased while flexural strength and fracture toughness decreased with the increasing of the ratio of Al-Zr intermetallics. Flexural strength and fracture toughness of Al43 were the highest reaching up to 396.0 MPa and 6.0 MPa.m 1/2 , respectively. The fracture modes of Ti 3 Al + TiAl, AlTi 2 + TiAl and Zr(Ti)Al + Al 3 (Ti, Zr) 5 lamellar structures were transgranular fractures, while fracture modes of Al-Zr intermetallics were intergranular fractures. The crack tip blunting and the effect of crack deflecting in Ti 3 Al + TiAl lamella led to increasing of flexural strength and fracture toughness. Besides, interlayer tearing of the three lamellar structures led to rising of flexural strength. [ABSTRACT FROM AUTHOR]

The multilayer Ti and Ni foils were designed to braze SiO 2 -BN diphase ceramic with Nb at 1140 °C for 5min. The interfacial microstructure was examined using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD) methods, respectively. Experimental results and thermodynamical calculations showed that the interfacial microstructures between Nb and SiO 2 -BN ceramic were (βTi,Nb)-TiNi eutectic structure/TiNi + TiNi 3 /TiN + Ti 3 O 5 + TiB 2 + Ti 5 Si 3 . The effects of the Ti content in the Ti-Ni braze alloy on the microstructures of the joints were investigated. With the increase of the Ti content, less Ni 3 Nb formed in the joint and TiNi 3 phase successfully turned into TiNi and Ti 2 Ni. The effects of the Ti content in the Ti-Ni braze alloy on the shear strength of the joints showed that the optimum thickness of the TiN + Ti 3 O 5 + TiB 2 + Ti 5 Si 3 reaction area was about 13 μm and the maximum shear strength of 52 MPa was achieved when the Ti content was 45 wt.%. [ABSTRACT FROM AUTHOR]

A novel composite interlayer with a reinforced network was designed using a SiC ceramic with a network structure and Ti-Ni-Nb composite filler foils, to which the Nb and BN-SiO 2 ceramic were successfully brazed under vacuum. For a brazing temperature of 1160 °C and holding time of 10 min, the interfacial microstructure of the Nb/BN-SiO 2 ceramic joint was Nb/(βTi,Nb)-TiNi eutectic structure+(βTi,Nb) 2 Ni+SiC+TiC/TiN+Ti 2 N+TiB+Ti 5 Si 3 +TiO/BN-SiO 2 ceramic. In addition, the shear strength and nano-hardness were analyzed to evaluate the effect of the composite interlayer with a network reinforcement architecture on the mechanical properties of the joint. During brazing, the Ti-Ni-Nb filler metal infiltrated and reacted with the SiC to form the network reinforcement architecture, resulting in the residual stress being relieved and the mechanical performance of the joint being significantly improved. A maximum shear strength of 102 MPa was achieved, which was 60 MPa (142%) higher than that of the joint brazed without the network reinforcement architecture. A reduction in the residual stress on the BN-SiO 2 ceramic side from 328 MPa to 210 MPa was observed with the network reinforcement architecture, and the fracture path of the joint changed from the surface of the BN-SiO 2 ceramic to the interfacial reaction zone. [ABSTRACT FROM AUTHOR]

Femtosecond laser beam cutting is becoming widely used to meet demands for increasing accuracy in micro-machining. In this paper, the effects of processing parameters in femtosecond laser beam cutting on the kerf size and microstructure in Inconel 738 have been investigated. The defocus, pulse width and scanning speed were selected to study the controllability of the cutting process. Adjusting and matching the processing parameters was a basic enhancement method to acquire well defined kerf size and the high-quality ablation of microstructures, which has contributed to the intensity clamping effect. The morphology and chemical compositions of these microstructures on the cut surface have been characterized by a scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Additionally, the material removal mechanism and oxidation mechanism on the Inconel 738 cut surface have also been discussed on the basis of the femtosecond laser induced normal vaporization or phase explosion, and trapping effect of the dangling bonds. [ABSTRACT FROM AUTHOR]

Highlights: [•] Depth-related microstructure of the modified layer of M50NiL steel is analyzed. [•] Depth-related wear mechanisms of RE treated layer of M50NiL steel is investigated. [•] The relationship between phase structure, hardness and wear mechanism is studied. [Copyright &y& Elsevier]

Abstract: Some factors contributing to the hot ductility losses of a 2.25Cr–1Mo steel were identified over the temperature range 750–950°C, after the specimens were austenitized at 1000°C, furnace cooled to different temperatures, and held there for sufficient periods of time, followed by tensile testing. There were two types of ferrite present in the microstructure, namely, pro-eutectoid ferrite and deformation-induced ferrite. The pro-eutectoid ferrite was only formed below Ar 3 (∼825°C), which was nucleated on the inclusions and distributed uniformly. Nevertheless, the deformation-induced ferrite was formed in a much wider temperature range. It was distributed mainly along austenite grain boundaries above Ar 3, and around the pro-eutectoid ferrite below Ar 3. The deformation-induced ferrite had a primary effect on the hot ductility, which was mainly responsible for a hot ductility trough. There was a peak in the quantity of deformation-induced ferrite between 800 and 900°C, which was just corresponding to the hot ductility trough. The morphology of ferrite was also essential. The net-like structure of ferrite formed along austenite grain boundaries was the most deleterious to the hot ductility. [Copyright &y& Elsevier]

The paper focuses on the solidification especially on the liquid phase separation of Cu-35 at, % Cr alloys under various cooling rates. When the solidification temperature is below the liquidus and above the spinodal temperature, solidification runs normally, with the growth of primary Cr-rich dendrites. When the solidification temperature is below the spinodal temperature, liquid phase separation should occur through the solidification process and the primary Cr-rich phase has a special nodular structure under an appropriate cooling rate. Large Cr-rich particles obtained from liquid phase separation can grow by absorbing smaller ones via the transfer of matter. Furthermore, some particles collide with each other, mutually losing surface energy by joining to form a single particle. The size of the Cr-rich particles obtained from liquid phase separation decreases with increasing cooling rate. Using thermodynamic calculations and referring to literature data, the viewpoints on liquid phase separation are systematized and applied to the CuCr system. Liquid phase separation in an undercooled liquid is not advantageous in refining the microstructure of alloys and should be restricted. [ABSTRACT FROM AUTHOR]

The wetting and interfacial reaction between the liquid Ag-Cu-Ti and SiO 2f /SiO 2 composites were studied at 860 °C for various holding durations. Typical interfacial microstructure of the AgCuTi-SiO 2f /SiO 2 system was firstly investigated. The formation sequence of the reaction layers was discussed. Then the relationship between contact angles and the types of reaction products were revealed. Results show that the formation of the Cu x Ti 6-x O (x = 2, 3) phase plays a key role on the wettability of the AgCuTi-SiO 2f /SiO 2 system. The microstructural evolution of the reaction products at the AgCuTi-SiO 2f /SiO 2 interface versus various holding durations was studied. Finally, the wetting mechanism of the AgCuTi-SiO 2f /SiO 2 system was proposed. This study can offer new insights into the reaction and joining nature of the AgCuTi-SiO 2f /SiO 2 system. • Ti 5 Si 3 + TiO 2 /Cu x Ti 6-x O (x = 2, 3) reaction layer formed for the AgCuTi-SiO 2f /SiO 2 wetting system. • Ti 5 Si 3 + TiO 2 proved to form first and Cu x Ti 6-x O(x = 2, 3) layer formed subsequently. • Cu x Ti 6-x O(x = 2, 3) layer became unstable with the extension of the holding duration. • Cu x Ti 6-x O(x = 2, 3) layer was the key that promoted the wetting of the SiO 2f /SiO 2 by AgCuTi. • 4 stages were divided for the wetting process of the AgCuTi-SiO 2f /SiO 2 system. [ABSTRACT FROM AUTHOR]

The Nb and Nb/Ni interlayers were designed for the diffusion bonding of the hydrogenated TC4 alloy and GH3128 superalloy joint. Typical microstructure of the TC4-0.3 H/Nb(Ni/Nb)/GH3128 joints were investigated. The effects of holding temperatures and durations on the microstructure evolution of the hydrogenated TC4/GH3128 joints were investigated. The addition of a Nb interlayer can successfully suppress the brittle Ti-Ni phase formation and the maximum joint strength reached 245 MPa bonded at 860 ℃/60 min under 10 MPa. The design of the Nb/Ni interlayer successfully eliminated the unbonded voids and the Ni-Cr layer formed when bonding with a single Nb interlayer. The maximum shear strength of ˜270 MPa was achieved when bonding at 860 ℃ for 80 min under 10 MPa. Fracture mechanism of the hydrogenated TC4/GH3128 joints bonded with two interlayers were analyzed finally. [ABSTRACT FROM AUTHOR]

Abstract A graphene nanosheets reinforced Ag-Cu composite filler (Ag-Cu + GNSs) was developed by introducing GNSs into Ag-Cu powder filler. Unidirectional carbon fiber reinforced lithium aluminosilicate matrix composites (UD-C f /LAS composites) and Ti–6Al–4V alloy were brazed with Ag-Cu + GNSs composite filler. The typical interfacial microstructure of joint was Ti–6Al–4V/Ti(s,s)/Ti 2 Cu/TiCu/Ag(s,s)/Ti 3 Cu 4 /Cu(s,s)+TiCu + TiC/Ti 3 Cu 4 /TiC + TiSi 2 /UD-C f /LAS composites. The in situ synthesized TiCu + TiC composite from the reaction between Ti and GNSs had the following benefits: 1) refined the microstructure of the joint; 2) reinforced the joint; 3) alleviated the thermal stress of the joint by constraining the growth of continuous Ti 3 Cu 4 intermetallic layers. Moreover, with the increase of GNSs content, the amount of TiCu + TiC phases increased. Ag(s,s) and Ti 3 Cu 4 became uniform and fine in the interlayer. Both the thickness of reaction layers and the size of granular Ti 3 Cu 4 and TiCu + TiC phases firstly increased and then decreased with the rise of the brazing temperature. On the contrary, the content of Ag based composite decreased at first and then increased. The highest shear strength of joints reached 45.5 MPa with 0.5% GNSs addition when brazed at 900 °C for 10 min. Based on the experimental results, the interface evolution mechanism of the Ti–6Al–4V/Ag-Cu + GNSs/UD-C f /LAS composites joint was investigated. Highlights • TC4/C f /LAS composites joints were brazed by GNSs reinforced composite filler. • The determination of interface reaction phases was realized by TEM. • Brazing temperature and addition of GNSs had influence on the joints microstructure. • The highest shear strength of joints reached 45.5 MPa. • Microstructural evolution mechanism and reactions of brazed joints were expounded. [ABSTRACT FROM AUTHOR]

Al x CrFeNi eutectic multi-component alloys were prepared to obtain excellent mechanical properties by double-phase strengthening. The X-ray diffraction results showed that the crystal structure were both body-centered cubic and energy-dispersive X-ray spectrometer identified that the two phases are ordered NiAl intermetallic and disordered [Fe, Cr] solid solution. The formation of eutectic structures was introduced by a simplified dynamic model. After mechanical tests, the alloys presented excellent compressive strength and unexpected large deformation. Due to the solid solution and fine-grain strengthening resulted by Al addition, mechanical properties of Al x CrFeNi alloys exhibited regularity in some degree. Among all alloys, Al 1.3 CrFeNi has the highest fracture strength and Al 0.9 CrFeNi has the most excellent strain. Besides, Al 1.2 CrFeNi alloy showed a good combination of strength and ductility. [ABSTRACT FROM AUTHOR]

Pulsed plasma arc additive manufacturing (PPAM) is a novel additive manufacturing (AM) technology due to its big potential in efficiency, convenience and cost-savings comparing with other AM process. In this research, several Ti-6Al-4V thin walls were deposited by an optimized weld wire-feed PPAM process, in which the heat input was gradually decreased layer by layer. The deposited thin wall consisted of various morphologies with different microstructure, such as epitaxial growth of prior β-grains, martensite and horizontal layer bands of Widmanstätten, which depend on the heat input, multiple thermal cycles and gradual cooling rate in the deposition process. Reducing heat input of each bead and using pulsed current in the PPAM process, the microstructure of thin wall was refined. Meanwhile, the thin wall was strengthening and toughening. The average yield strength (YS) and ultimate tensile strength (UTS) reach 909 MPa and 988 MPa, respectively, and elongation reaches about 7.5%. The thin wall exhibited excellent performance in the aeronautical applications owing to the high values of mechanical properties in the room temperature. [ABSTRACT FROM AUTHOR]

The Fe-Si-Al soft magnetic powder cores with five particle size distributions were prepared. The microstructure study revealed that the cores had a fairly compacted structure with a uniform insulation layer of the phosphate forming on the surface of the magnetic particles. The particle size distribution was found to have the great influence on the core's magnetic properties. The increase of the percentage of the small particles results in the decrease of the effective permeability, the improvement of the DC-bias performance, and the deterioration of the core loss. The effects of the distributed air gap and the demagnetization field on the core's magnetizing process were believed to be the underlying physical origins. The core losses at the frequencies lower and higher than 150 kHz were found to be mainly determined by the hysteresis loss and the eddy-current loss, respectively. The good magnetic performances of the Fe-Si-Al powder cores with the effective permeability of about 55-60 were finally achieved as follows: the percent permeability at 100 Oe is up to 52.3 %, and the lowest core loss at 50 kHz/1000 Gs is 270 mW cm. [ABSTRACT FROM AUTHOR]

In this study, the corrosion behaviours of molybdenum (Mo) and a Mo-based alloy (TZM) were investigated using a static immersion corrosion technique. Weight loss, surface microstructure, and corrosion depth of Mo and the TZM alloy were correlated with elements. The compatibility of Mo and the TZM alloy in static liquid Li was suitable. Mo demonstrated uniform corrosion with a homogenous dissolution of free C and Mo, and TZM alloy exhibited a nonuniform corrosion behaviour with a preferential grain boundary attack caused by the selective dissolution of free C, Ti, and Zr. When the surface oxidation layer of the samples was consumed, free C from Mo and TZM diffused into molten Li to form Li 2 C 2 and then was captured by Zr, Ti, and Mo to form thermodynamically stable carbides, which resulted in the enrichment of the C layer near the sample surfaces. In addition, Ti and Zr acted as N-trappers in liquid Li; the formation of Zr and Ti nitrides resulted in the enrichment of N, Ti, and Zr elements on the surface and led to TZM corrosion increase. Thus, Zr and Ti depletion, pitting, and grain boundary corrosion were problematic for TZM under long-term exposure to liquid Li. Reducing the content of free C and nonmetallic N and increasing the amount of Ti and Zr carbides on the surface of and inside the raw TZM alloy helped improve the corrosion resistance of TZM in liquid Li. • Corrosion behaviors of Mo and TZM exposed to liquid Li at 623 K for 1300 h were investigated and compared. • The corrosion mechanism of Mo and TZM in liquid Li was discussed. • Mo demonstrates a homogeneous corrosion while TZM shows a nonuniform corrosion. • Suggestions to alleviate the corrosion of Mo based alloy in liquid Li were put forward. [ABSTRACT FROM AUTHOR]

The present investigation is mainly focused on friction stir additive manufactured (FSAM) 2195 Al-Li alloy in aspects of localized microstructure evolution and mechanical performance. Characterization of the localized microstructure was conducted by optical microscope (OM), electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM) techniques, and mechanical properties were evaluated based on micro-hardness and tensile testing measurements. Results showed a build of multilayered stack of 2195 aluminum lithium alloy was fabricated using FSAM via multi-pass processing. Defects such as voids or kissing bond were not identified, and fine equiaxed grains were observed in the nugget zone (NZ). The decrease of average grain size and low angle boundaries (LABs) along the depth of the NZ was attributed to repetitive stirring action of the rotating tool. Distribution of precipitation phase is mainly determined by the thermal cycle. Numerous T 1 and θ ′ precipitates were identified in the base material (BM), which are beneficial to improve material hardness and thus strength. These precipitates were dissolved in NZ and thermo-mechanically affected zone (TMAZ), and coarsen in heat affected zone (HAZ), which caused loss of hardness and strength. Similarly, precipitate morphology, size, and distribution are different in the built direction. Excellent tensile strength and elongation were identified in the NZ, which is attributed to fine grains and desirable precipitate characterization. • Defect-free build was fabricated using friction stir additive manufacturing. • Microstructure. evolution was clarified in detail by EBSD and TEM. • Local mechanical properties was evaluated using hardness mapping and DIC. [ABSTRACT FROM AUTHOR]

Highlights: [•] First systematic study on dissimilar FSW of AA6061 and AA7075 Al alloys. [•] The effects of materials position and welding speed were investigated. [•] All joints failed in HAZ on the AA6061 side where hardness minima is located. [•] The UTS of joints increases with the decrease of heat input. [•] The highest UTS reached 245MPa which is 32% higher than required in AWS standard. [Copyright &y& Elsevier]

Abstract: The refinement in weld metal grain size and shape results in both improved mechanical properties (ductility and toughness) as well as a significant improvement in weldability. In the present study, the influence of scandium (Sc) additions to the fillers on the structure and mechanical properties of AA6082 gas tungsten arc (GTA) weldments were investigated. Controlled amounts of scandium as grain refiner were introduced into the molten pool of AA6082 by pre-deposited cast inserts (AA4043 and AA5356) by GTA welding. Full penetration GTA welds were prepared using alternating current (AC). It was observed that grain size decreased with increasing amounts of scandium. The grain refinement is mainly caused by the Al3Sc particles, which act as heterogeneous nucleation of α-Al grains. It has been shown that welds prepared with AA5356 cast insert exhibited high strength and ductility when compared with other welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, strength and ductility. Post-weld aging treatment resulted in improved tensile strength and hardness of the weldments and this aging response could be attributed to the weld dilution from the base metal. The slow diffusion of Sc in Al matrix and stability of Al3Sc precipitates at elevated temperatures were suggested to be responsible for the improved high temperature yield strength of welds made from Sc modified fillers. [Copyright &y& Elsevier]

Thermosetting polymer gel electrolytes (TPGEs) based on poly(acrylic acid)-poly(ethylene glycol) (PAA-PEG) hybrid were prepared and applied to fabricate dye-sensitized solar cells (DSCs). N-methylpyrrolidone (NMP) and γ-butyrolactone (GBL) were used as solvents for liquid electrolytes and LiI and KI as iodide source, separately. The microstructure of PAA-PEG shows a well swelling ability in liquid electrolyte and excellent stability of the swollen hybrid. The TPGE was optimized in terms of the liquid electrolyte absorbency and ionic conductivity photovoltaic performance. Quasi-solid-state DSCs containing TPGE with optimized KI electrolyte show higher efficiency, voltage, fill factor, and lower photocurrent than those with LiI electrolyte. The related mechanism was discussed. A quasi-solid-state DSC fabricated with optimized polymer gel electrolyte obtained an overall energy conversion efficiency of 4.90% under irradiation of 100 mW/cm2 (AM1.5). [ABSTRACT FROM AUTHOR]

The effect of annealing temperature on the magnetic and giant magnetostriction (GMS) of [Fe/Tb/Fe/Dy]n multilayer films were investigated. X-ray diffraction showed that the multilayer films' microstructures were still in amorphous at annealing temperature 300°C. The multilayer films began to crystalline at annealing temperature 400°C. The saturation magnetization of multilayer films increased by the increasing annealed temperature. The coercivity first decreased at annealing temperature 300°C and then increased when the annealing temperature was higher than 400°C. The multilayer films had good low-field GMS, and the magnetostriction of the multilayer films increased by the increasing annealing temperature. [ABSTRACT FROM AUTHOR]

An improved chemical bath deposition (CBD) technique has been provided to prepare zinc sulfide (ZnS) thin films on glass substrates deposited at 80–82°C using a mixed aqueous solution of zinc sulfate, ammonium sulfate, thiourea, hydrazine hydrate, and ammonia at the alkaline conditions. Both the traditional magnetic agitation and the substrates vibration by hand frequently were done simultaneously during the deposition. The substrates vibration reduced the formation and residence of gas bubbles on the glass substrates during growth and resulted in growth of clean ZnS thin films with high quality. Ammonia and hydrazine hydrate were used as complexing agents. It is found that hydrazine hydrate played an important role in growth of ZnS films. The structure and microstructure of ZnS films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-vis spectroscopic methods. The XRD showed a hexagonal structure. The formed ZnS films exhibited good optical properties with high transmittance in the visible region and the band gap value was estimated to be 3.5–3.70 eV. [ABSTRACT FROM AUTHOR]

The microstructures and resistivities of melt-spun Cu75Cr25 and Cu(75-x)Cr25Nix (x = 1 or 3 wt. %) ribbons were studied. The size of the Cr-rich phase from liquid phase separation in the Cu75Cr25 microstructure can be decreased from the micrometer-scale to about 250 nm by using melt spinning. After annealing at 600 °C for 3 h, the resistivity of Cu75Cr25 ribbon can meet the needs of contact. On the melt-spun base, alloying by Ni could further decrease the size of the Cr-rich phase from 250 nm to about 150 nm. However, when the Ni content is higher than or equal to 3%, the resistivity of annealed Cu75-Cr25Nix (x ≥ 3) ribbons is too high to be used by the medium-voltage vacuum interrupters. For nano-grained CuCr alloys, its lower arc chopping current is advantageous to the use of contact and the circuitry protect, its long arc trace route and high velocity of spot direction motion could mitigate the partial ablate of cathode surface and the lifetime of contact could be prolonged. [ABSTRACT FROM AUTHOR]

Intrinsic zinc oxide (i-ZnO) film was prepared for CuInSe2 (CIS) solar cell application [L. Stolt and J. Hedstrom, Appl. Phys. Lett.62 (1993) 8; D. Rudmann, Ph.D. Thesis, University of Basel, Basel, (2004)] on glass substrate by inductively coupled plasma (ICP)-assisted DC magnetron sputtering and under a quite low temperature of 50°C. The sputtering was done in an Ar and O2 gas mixture and a ceramic ZnO target was used. The microstructures of the film were investigated by X-ray diffractometer and scanning electron microscope. It was shown that all of the films had a c-axis preferred orientation perpendicular to the substrate. In our work, film with resistivity of 7 × 108Ω·cm and transmittance of about 80% in the visible range was prepared under the conditions of 4 mTorr working pressure and 50°C temperature. [ABSTRACT FROM AUTHOR]

Indium tin oxide (ITO) thin films were prepared by radio frequency (RF) magnetron sputtering and under a quite low vacuum level of 2.3 × 10-3Pa. The sputtering was done in an Ar and O2 gas mixture at a temperature of 200°C. A ceramic In2O3:SnO2 target (10 wt% SnO2) was used. The microstructures of the films were investigated by a field emission scanning electron microscope (FESEM) and an X-ray diffractometer (XRD). X-ray photoelectron spectroscopy (XPS) was performed to characterize the composition of the films. ITO films with a high transparency in the visible wavelength range (80–95%) were obtained. The dependency of the electrical, optical and structural properties of ITO films on both the O2 flow ratio (O2/(O2 + Ar)) and the working pressure was investigated. In the case of low working pressure (1 Pa), the more highly transparent and conducting films were produced at the lower O2 flow ratio. High working pressure (2 Pa) gave rise to low quality, low transparency and amorphous films. Under RF sputtering at low vacuum level, the main contribution to the chamber atmosphere is due to water vapor. Oxygen originating from water vapor dissociation induced by plasma plays the same role as an oxygen or water vapor flux usually intentionally introduced in the system in order to have good quality films. [ABSTRACT FROM AUTHOR]