In this study, hydrogen was determined in the ER5183 wires for MIG welding, and the effect of hydrogen in the wires on the tensile strength as well as the fracture behavior of Al–Mg MIG weld were ...investigated in order to clarify the affecting mechanism by hydrogen, which provided a reasonable range of hydrogen content in ER5183 welding wires. The results showed that, with the increasing hydrogen content, the tensile strength of the corresponding welds decreased accordingly. During the fracture process of the weld, hydrogen played serious roles as follows, accelerating the fracture process, promoting the formation of pores and causing the decohesion of the inclusion and matrix. By the mechanisms mentioned above, hydrogen changed the feature of fracture morphology from dimples to various defects. Considering the high tensile strength as well as the fine microstructure of the welds, the hydrogen content of the ER5183 welding wires should be controlled below 0.18 μg/g.
•Determining the hydrogen content in the ER5183 welding wires for MIG welding.•Investigating the effect of hydrogen content on the tensile strength as well as the fracture behavior of Al–Mg MIG weld.•Finding the decohesion phenomenon, crack and porosity in the weld microstructure.•Giving a reasonable range of hydrogen content in ER5183 aluminum welding wire.
The reliability of wide-bandgap (WBG) semiconductors used as power electronics is closely related to the high thermal conductivity of AlN-metalized substrates. Thus, the bonding of AlN ceramics with ...metals is a key issue for the production of reliable AlN-metalized substrates. This paper reports on a new method for producing AlN/Cu joints by employing a novel film metallization production process, which involves a porous network of Cu layer and Ag foil. The microstructure and the phases formed at the interface of the AlN/Cu joints produced at various brazing temperatures and times were analyzed by scanning electron microscopy and X-ray diffraction analysis. Strong joints with shear strength of 48.5 MPa were produced after brazing at 850 °C for 10 min. The typical microstructure at the interfacial reaction zone was Cu/Ag(s) + Cu(s)/CuAlO
2
+ Al
2
O
3
+ Cu(s)/AlN. The experimental results manifest the crucial role of the Ag–Cu eutectic liquid phase, formed by the reaction between the Cu layer and the Ag foil, and of the porous network of the Cu layer deposited on the surface of the AlN ceramic substrate, since both of them effectively favor the reduction in the residual thermal stresses in the joint and result in strong ceramic/metal joins.
Herein, a bio-based plasticizer ketalized tung oil butyl levulinate (KTBL) was developed using methyl eleostearate, a derivative of tung oil, and butyl levulinate. KTBL can be used as an auxiliary ...plasticizer to partially replace traditional plasticizer. The plasticizer has a ketone structure, an ester base, and a long linear chain. It was mixed with dioctyl phthalate (DOP), and the effect of the plasticizer KTBL as an auxiliary plasticizer on the plasticization of poly(vinyl chloride) (PVC) was studied. Their compatibility and plasticizing effect were evaluated using dynamic-mechanical thermal analysis (DMA), mechanical property analysis, and thermogravimetric analysis (TGA). The results demonstrate that when the KTBL to DOP ratio is 1:1, the blended sample with KTBL exhibits superior mechanical performance compared to pure DOP, resulting in an increased elongation at break from 377.47% to 410.92%. Moreover, with the increase in KTBL content, the durability is also significantly improved. These findings suggest that KTBL can serve as an effective auxiliary plasticizer for PVC, thereby reducing the reliance on DOP.
Different microstructures were obtained under various thermal conditions by adjusting the heat treatment parameters of the Cr-Co-Ni-Mo series of ultra-high strength stainless steel. The effect of ...organizational evolution on the stress corrosion cracking (SCC) of the Cr-Co-Ni-Mo series of ultra-high strength stainless steel was investigated using potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and other test methods in combination with slow strain rate tensile tests (SSRTs). The results show that the Mo- and Cr-rich clusters and precipitation of the Laves phase reduce the corrosion resistance, while increasing the austenite content can improve the corrosion resistance. The Cr-Co-Ni-Mo series of ultra-high strength stainless steel has a high SCC resistance after quenching at 1080 °C and undergoing deep cooling (DC) treatment at -73 °C. With increasing holding time, the strength of the underaged and peak-aged specimens increases, but the passivation and SCC resistance decreases. At the overaged temperature, the specimen has good SCC resistance after a short holding time, which is attributed to its higher austenite content and lower dislocation density. As a stable hydrogen trap in steel, austenite effectively improves the SCC resistance of steel. However, under the coupled action of hydrogen and stress, martensitic transformation occurs due to the decrease in the lamination energy of austenite, and the weak martensitic interface becomes the preferred location for crack initiation and propagation.
B-site oxide precursor method was utilized to synthesize Ba
3
MgNb
2
O
9
ceramics. The effects of sintering temperature on phase composition of Ba
3
MgNb
2
O
9
ceramics was evaluated by the X-ray ...diffraction. Experimental results indicated that all prepared Ba
3
MgNb
2
O
9
ceramics exhibited 1:2 ordered hexagonal structure. The second phase Ba
5
Nb
4
O
15
can emerge in all ceramics due to the decrease of activation energy of reaction, leading to the splitting of E
g
(O) vibration mode in the Raman spectra. In addition, lattice parameters of 1:2 ordered phase were obtained from the refinement of XRD patterns. The maximum value of c/a ratio occurred at 1475 °C, meanwhile the ceramics showed the highest 1:2 ordered degree and excellent
Q
×
f.
It was also found that the uniform grain-size distribution of Ba
3
MgNb
2
O
9
powder were important factors for preparing dense Ba
3
MgNb
2
O
9
ceramics. Moreover, B-site oxide precursor method can not only effectively lower the densification temperature from 1650 to 1475 °C, but also increase the quality factor (
Q
×
f
) by about 90.8%, i.e., from 55,277 to 105,467 GHz.
With the development of electronic components towards high power, high packaging density, and miniaturization of device size, heat dissipation and the electromagnetic interference problems between ...the electronic components are emerging. In order to solve the undesirable electromagnetic wave and heat emissions produced by electronic device simultaneously, the electronic packaging materials with high thermal conductivity and anti-electromagnetic interference are highly expected. In this work, NiFe
2
O
4
-modified short carbon fibers (SCF) were designed and prepared. NiFe
2
O
4
were in situ grown on the surface of SCF by hydrothermal method. The chemical structure and morphology of SCF-NiFe
2
O
4
were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The microwave absorbing performance test shows that SCF-NiFe
2
O
4
possess superior microwave absorbing performance, where the minimum reflection loss is − 20.7 dB. Finally, SCF-NiFe
2
O
4
/epoxy resin composites were prepared by introducing SCF-NiFe
2
O
4
as thermal conductive filler into epoxy resin. The surface-modified SCF with NiFe
2
O
4
is more easily infiltrated by resin and exhibits strong interfacial interaction with the matrix. With the increase of the content of SCF-NiFe
2
O
4
, the thermal conductivity of the composites increases obviously. When the content of SCF-NiFe
2
O
4
reaches 20 vol%, the composites show better thermal conductivity, and the thermal conductivity reaches 1.03 W/m K.
In this paper, an insulating film was successfully prepared by sintering 35 wt % CaO-15 wt % Al
O
-10 wt % B
O
-40 wt % SiO
glass at 875 °C. After sintering, the main component of the insulating film ...was glass-ceramics. The main crystal phase was CaAl
Si
O
, and the crystallization activation energy was 189.76 kJ/mol. After preparing the insulating film, its color turned yellow, and the diffusion of Ag was found by XPS and XRD data. When the temperature increased to 875 °C, the color of the insulating film became lighter, and the silver content decreased. The adhesion of the multilayer structure could reach 875 N. The dielectric constant of the insulating film in the multilayer structure was approximately 5, and the dielectric loss was 0.0011. After sintering, the dielectric strength of the insulating film could reach 13.11 kV/mm, which fully meets the requirements of a complex packaging structure.
Bio-based vitrimers present a promising solution to the issues associated with non-renewable and non-recyclable attributes of traditional thermosetting resins, showcasing extensive potential for ...diverse applications. However, their broader adoption has been hindered by the requirement for catalyst inclusion during the synthesis process. In this study, a cardanol-based curing agent with poly-hydroxy and tertiary amine structures was prepared by a clean synthetic method under the theory of click chemistry. The reaction of a cardanol-based curing agent with diglycidyl ether of bisphenol A formed catalyst-free, self-healing, and recyclable bio-based vitrimers. The poly-hydroxy and tertiary amine structures in the vitrimers promoted the curing of epoxy-carboxylic acid in the cross-linked network and served as internal catalysts of dynamic transesterification. In the absence of catalysts, the vitrimers network can achieve topological network rearrangement through dynamic transesterification, exhibiting excellent reprocessing performance. Moreover, the vitrimers exhibited faster stress relaxation (1500 s at 180 °C), lower activation energy (92.29 kJ·mol
) and the tensile strength of the recycled material reached almost 100% of the original sample. This work offers a new method for preparing cardanol-based epoxy vitrimers that be used to make coatings, hydrogels, biomaterials, adhesives, and commodity plastics in the future.
Abstract
In the temperature range of 1000 °C–1150 °C and the holding time range of 30–150 min, the effect of niobium (Nb) on the behavior of grain growth and the evolution pattern of the mechanical ...properties of a martensitic stainless steel was studied. This study found that the addition of Nb allowed a large amount of undissolved NbC phase to be present in the steel, that the dragging effect of the solute atoms such as solute Nb and Mo reduced the migration rate of the grain boundary , and the pinning effect of NbC hindered the growth of grains, and that the growth rate of grains in 0.11Nb steel was slow in the temperature range of 1000 °C–1080 °C and increased significantly at the temperature range of 1080 °C–1150 °C. Next, the kinetic equations of the grain growth of 0.002Nb steel and 0.11Nb steel were constructed. The second phase strengthening of NbC and the fine grain strengthening jointly increased the yield strength of the steel but reduced the plasticity and ultimate tensile strength (UTS) of the steel. The addition of Nb had a minor effect on the content of retained austenite in the steel, but its refining effect on the hierarchical martensite microstructure increased the number of nucleation sites of retained austenite, reduced their sizes, made their distribution more dispersed, and more effectively hindered crack propagation, thus improving the toughness of the steel.
A kind of polymer composite was fabricated using polystyrene as the matrix and Si3N4 powder as filler employing the method of heat press molding. Microstructure, thermal conductivity and dielectric ...constant of the Si3N4 filled composite were evaluated. The effect of the volume fraction of Si3N4, the particle size of the polystyrene matrix and the silane treatment of Si3N4 filler on the thermal conductivity of the composite was investigated; dielectric constant of the composite was evaluated. The main factors that affect the thermal conductivity of the composite were confirmed through theoretical analyzing of the experimental data and the thermal conductivity model. Experimental results show that with the filler content increasing, a thermally conductive network is formed in the composites, thus the thermal conductivity of the composite increases rapidly. The composites experience a highest thermal conductivity of 3.0W/mK when the volume fraction of the filler reaches 40%. The increasing of thermal conductivity is dominated by the ease of forming a thermal conductive network. A larger polystyrene particle size, a higher Si3N4 filler content and the silane treatment of the filler have a beneficial effect on improving the thermal conductivity. The dielectric constant increases with the content of Si3N4 filler, however, it remains at a relatively low lever ( < 4, at 1MHz).
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