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Welding of Dissimilar Steel/Al Joints Using Dual-Beam Lasers with Side-by-Side Configuration
摘要： Welding of dissimilar steel/Al lapped joints of 1.5 mm in thickness was carried out by using dual-beam laser welding with side-by-side configuration. The effect of the major process parameters including the dual-beam power ratio of (Rs) and dual-beam distance (d1) on the steel/Al joint characteristics was investigated concerning the weld shape, interface microstructures, tensile resistance and fracture behavior. The results show that dual-beam laser welding with side-by-side configuration produces soundly welded steel/Al lapped joints free of welding defects. The processing parameters of Rs and d1 have a great influence on the weld appearance, the weld penetration in the Al alloy side (P2) and the welding defects. Variation in the depth of the P2 and the locations at the Al/weld interface cause heterogeneous microstructures in the morphology and the thickness of the intermetallic compound (IMC) layers. In addition, electron back scattered diffraction (EBSD) phase mapping reveals that the IMC layer microstructures formed at the Al/weld interface include the needle-like θ-Fe4Al13 phases and compact lath η-Fe2Al5 layers. Some very fine θ-Fe4Al13 and η-Fe2Al5 phases generated along the weld grain boundaries of the steel/Al joints are also confirmed. Finally, there is a matching relationship between the P2 and the tensile resistance of steel/Al joints, and the maximum tensile resistance of 109.2 N/mm is obtained by the steel/Al joints produced at the Rs of 1.50 during dual-beam laser welding with side-by-side configuration. Two fracture path modes have taken place depending on the P2, and relatively high resistance has been achieved for the steel/Al joints with an optimum P2.
关键词： dual-beam laser welding,tensile resistance,side-by-side configuration,EBSD phase mapping,steel/Al joint
更新于2025-11-28 14:24:20
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High Temperature Oxidation and Wear Resistance of In Situ Synthesized (Ti3Al?+?TiB)/Ti Composites by Laser Cladding
摘要： (Ti3Al + TiB)/Ti composites were prepared on Ti6Al4V by laser cladding. The microstructures of the coatings were analyzed; the high temperature wear and oxidation properties of the coatings were investigated and compared with Ti6Al4V. Ti3Al and TiB particles were in situ formed through the reaction between Ti and AlB2. The reinforcements exhibited some crystallographic orientation relationships with a-Ti matrix, and a semi-coherent interface (Ti3Al) or a coherent interface (TiB) was obtained. The weight gain of the coating under each combination of temperature and time condition was 20 to 30 pct of the value of Ti6Al4V under the same experimental parameters. A denser and well-bonded TiO2 + Al2O3 layer was formed, effectively hindering the oxygen diffusion compared with the TiO2 layer on Ti6Al4V. EBSD result showed that the Al2O3 mainly assembled into clusters and located close to the interface while the outer area of the oxidation layer was mainly TiO2. The friction coefficients and wear losses of the coatings were lower than those of the substrates at 300 °C to 750 °C. The oxidation was a crucial factor affecting the wear performance at high temperatures. The protective effect of the TiO2 + Al2O3 layer and the formation of transfer films on the worn surface contributed to the improved wear resistance of the coating.
关键词： TiB,Laser Cladding,Wear Resistance,Ti Composites,In Situ Synthesized,High Temperature Oxidation,Ti3Al
更新于2025-11-28 14:24:20
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Computational and Experimental Investigation of Micro-Hardness and Wear Resistance of Ni-Based Alloy and TiC Composite Coating Obtained by Laser Cladding
摘要： The influence of processing parameters on the micro-hardness and wear resistance of a Ni-based alloy and titanium carbide (TiC) composite cladding layer was studied. Mathematical models were developed to predict the micro-hardness and wear resistance of the cladding layer by controlling the laser cladding processing parameters. Key processing parameters were the laser power, scanning speed, gas flow, and TiC powder ratio. The models were validated by analysis of variance and parameter optimization. Results show that the micro-hardness is positively correlated with laser power and TiC powder ratio, where the TiC powder ratio shows the most significant impact. The wear volume decreased with an increasing TiC powder ratio. The targets for the processing parameter optimization were set to 62 HRC for micro-hardness and a minimal volume wear. The difference between the model prediction value and experimental validation result for micro-hardness and wear volume were 1.87% and 6.33%, respectively. These models provide guidance to optimize the processing parameters to achieve a desired micro-hardness and maximize wear resistance in a composite cladding layer.
关键词： Ni35A + TiC composite,laser cladding,central composite design,wear resistance,micro-hardness
更新于2025-11-28 14:24:20
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Boron-doped diamond with improved oxidation resistance
摘要： The oxidation behavior of pure and 0.2 wt% B-containing diamond powders was investigated by thermal analysis, SEM analysis, and Raman spectroscopy of partially oxidized diamonds. Boron-doped diamond exhibited a much higher oxidation stability than that of pure diamond. The maximum oxidation rate shifted from 773 °C for the pure diamond to 1118 °C for the B-doped diamond. SEM analysis of the surface of the partially oxidized diamonds revealed that the low boron content (0.2%) was sufficient for the formation of a protective B2O3 surface layer in the regions in which active oxidation took place. This layer was most probably the reason for the improved oxidation resistance.
关键词： Diamond,Boron-doped,Oxidation resistance
更新于2025-11-21 11:20:48
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Microstructure and Wear Resistance of 62Cu-38Zn Brass with Bionic Coupling Units Treated by Laser Cladding
摘要： In order to improve the wear resistance of 62Cu-38Zn brass, bionic coupling units were fabricated by laser cladding using Ni-based, Fe-based and Co-based self-fluxing alloy powders. The microstructures, chemical composition and mechanical properties of the units were studied in this paper. Wear resistance of samples was examined by dry sliding wear. Good metallurgical bonding between the unit and substrate was obtained, and fine dendritic microstructure was resulted in the unit zone, which proved marked availability of laser cladding on brass. Laser cladding treatments with different self-fluxing alloy powders were beneficial to reinforcing the surface of brass and then improved its wear resistance with various results. The Ni-based alloy powders led to the best wear resistance amongst the all samples.
关键词： wear resistance,laser cladding,bionic coupling units,microstructure,62Cu-38Zn brass
更新于2025-11-21 11:18:25
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Effect of graphene on corrosion resistance of Micro-arc oxidation coatings on 6061/7075 dissimilar laser-MIG hybrid welded joint
摘要： Corrosion behavior of a laser-metal inert gas hybrid (Laser-MIG) welded joint with dissimilar aluminum alloys was investigated. Micro-arc oxidation (MAO) coatings with and without graphenes were prepared on the surface of the welded joint. The effects of graphenes on the structure and corrosion resistance of the MAO coatings were studied. The welded joint was divided into five zones to investigate corrosion inducements in different zones. The heat-affected zone of 7075Al (7-HAZ) was found to be most susceptible to corrosion. Although the substrates in different zones had heterogeneous microstructures and phase compositions, the MAO coatings in different zones displayed relatively uniform surface morphology, structure, and phase composition. The MAO treatment significantly improved the corrosion resistance of welded joints. In addition, ceramic-graphene composite coatings exhibited slightly better corrosion resistance than a simple coating without graphenes due to structural changes in the coating.
关键词： Corrosion resistance,Aluminum,Graphene,Laser-MIG hybrid welding,Micro-arc oxidation
更新于2025-11-21 11:18:25
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Automated Quantification of Extranuclear ERα using Phosphor-integrated Dots for Predicting Endocrine Therapy Resistance in HR+/HER2? Breast Cancer
摘要： In addition to genomic signaling, Estrogen receptor alpha (ERα) is associated with cell proliferation and survival through extranuclear signaling contributing to endocrine therapy (ET) resistance. However, the relationship between extranuclear ERα and ET resistance has not been extensively studied. We sought to measure extranuclear ERα expression by immunohistochemistry using phosphor-integrated dots (IHC-PIDs) and to assess its predictive value for ET resistance. After quantitative detection of ERα by IHC-PIDs in vitro, we developed “the nearest-neighbor method” to calculate the extranuclear ERα. Furthermore, tissue sections from 65 patients with HR+/HER2- BC were examined by IHC-PIDs, and the total ERα, nuclear ERα, extranuclear ERα PIDs score, and ratio of extranuclear-to-nuclear ERα (ENR) were measured using the novel method. We demonstrate that quanti?cation of ERα using IHC-PIDs exhibited strong correlations to real-time qRT-PCR (r2 = 0.94) and ?ow cytometry (r2 = 0.98). High ERα ENR was signi?cantly associated with poor overall survival (p = 0.048) and disease-free survival (DFS) (p = 0.007). Multivariate analysis revealed that the ERα ENR was an independent prognostic factor for DFS [hazard ratio, 3.8; 95% CI, 1.4–11.8; p = 0.006]. Our automated measurement has high accuracy to localize and assess extranuclear ERα. A high ERα ENR in HR+/HER2- BC indicates decreased likelihood of bene?ting from ET.
关键词： estrogen receptor α,endocrine therapy resistance,breast cancer,prognostic,IHC-PIDs
更新于2025-11-21 11:08:12
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Origin of anisotropy and compositional dependence of phonon and electron transport in ZnO based natural superlattices and role of atomic layer interfaces
摘要： Reaction of ZnO with trivalent ions can form natural superlattice (SL) compounds, which possess unusual structural characteristics and strong anisotropic physical transport properties. In this work, by synthesizing strongly textured bulk polycrystals of pure SL phases and performing characterization and measurements for both in-plane and cross-sectional directions, we revealed the strongly crystal orientation dependent transport properties. The observed compositional or SL interface spacing dependent electrical conductivity is largely attributed to the overall doping of ZnO wurtzite regions. The atomic layer SL interfaces are phonon barriers, and the interfacial thermal (Kapitza) resistance depends on SL interface spacing. The transport direction perpendicular to these SL interfaces are electron-conductive paths with remarkably higher electron mobility. There are electron potential barriers associated with these atomic layer SL interfaces. The effective and absolute potential barrier heights are determined, which are proportional to the natural conduction band discontinuities. The current study provides new findings and knowledge about the role of SL interfaces in phonon and electron transport process in these ZnO based natural SLs. The present work can be useful and inspiring to design and modify complex layer-structured compounds, including synthetic superlattice systems, for a variety of applications where energy carriers transport is involved.
关键词： Interfaces,Superlattices,Electron potential barrier,Interfacial thermal (Kapitza) resistance,Thermal conductivity,ZnO
更新于2025-11-21 11:03:13
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Correlation between the morphology and the opto-electronic and electrical properties of organometallic halide perovskite (CH<sub>3</sub>NH<sub>3</sub>MH<sub>3</sub>) thin films
摘要： Organometallic halide perovskites are emerging as a promising class of materials for optoelectronic applications. Crystal morphology is important for improving the organic-inorganic lead halide perovskite semiconductor property in optoelectronic, electrical and photovoltaic devices. It is thus important to investigate how the changes in crystal morphology affect the semiconductor behavior. This work presents a study that was carried out to assess the relationship between different deposition methodologies and the opto-electronic and electrical properties of the resultant organometallic halide perovskite thin films. Herein, single step solution deposition method and two step solution deposition methods have been used to deposit perovskite thin films. The structure and morphology of perovskite was controlled by changing concentration, annealing temperatures and dip coating times. From the study, prepared films showed different morphologies as the concentration, annealing temperatures and dip coating times were varied. Optical band gap energies of 2.23 eV, 2.13 eV and 2.09 eV were obtained for samples prepared by single step solution deposition method and 1.57 eV, 1.55 eV and 1.52 eV for two step solution deposition method. The sheet resistance values decreased with an increase in concentration, annealing temperatures and dip coating times. The decrease in optical band gap energy and sheet resistances are excellent properties for high performance photovoltaic devices.
关键词： Perovskite,sheet resistivity,activation energy,band gap,sheet resistance,spectroscopy
更新于2025-11-19 16:56:35
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Photovoltaic Properties and Series Resistance of <i>p</i> -Type Si/Intrinsic Si/ <i>n</i> -Type Nanocrystalline FeSi <sub/>2</sub> Heterojunctions Created by Utilizing Facing-Targets Direct-Current Sputtering
摘要： p-Type Si/intrinsic Si/n-type nanocrystalline iron disilicide heterojunctions were created by utilizing facing targets direct-current sputtering at the pressure of 1.33 × 10?1 Pa that investigated the photovoltaic properties. They exhibited a large leakage current and a small energy conversion ef?ciency of 0.62%. From using the method of Nicollian and Brews, the series resistance (Rs) values at zero bias voltage were 7.40 Ω at 2 MHz and 7.57 Ω at 50 kHz, respectively, which were in agreement with that estimated by the means of Norde. From applying the method of Hill-Coleman, the interface state density (Nss) values were 3.15 × 1015 cm?2 eV?1 at 50 kHz and 8.93 × 1013 cm?2 eV?1 at 2 MHz. The obtained results revealed the presence of Rs and Nss at the junction interface, which should be the potential cause of spoiled photovoltaic performance in the heterojunctions.
关键词： Heterojunctions,Facing-Targets Direct-Current Sputtering,Nanocrystalline Iron Disilicide,Series Resistance,Interface State Density
更新于2025-11-14 17:28:48