- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
A comparison of microstructure and mechanical properties of laser cladding and laser-induction hybrid cladding coatings on full-scale rail
摘要： With the rapid development of high-speed and heavy-haul trains, the surface damages of rails are becoming more and more severe, and how to promote the surface strength of the rail and prolong its service life with high efficiency are becoming extremely important. Laser cladding (LC), with small heat affected zone (HAZ) and low dilution, is a promising novel way to hardface and repair the rail. However, there are two great barriers for the traditional LC to apply on full-scale rails: one is how to prevent the coating from cracking under the rapid heating and cooling cycle; the other is how to eliminate the martensite structure in HAZ, which may threaten the safety of railway transportation due to its high hardness and low fracture toughness and usually be forbidden in almost all the Railway Standards over the world. In this paper, laser-induction hybrid cladding (LIHC) was innovatively proposed to deposit Ni-based coatings on a full-scale rail. The cracking behaviors, microstructures and mechanical properties of the coatings and HAZs by LC, LIHC with induction pre-heating (pre-LIHC) and LIHC with induction post-heating (post-LIHC) were studied systemically. The results indicate that the cracking and martensite transformation occurred in the HAZ can only be prevented by post-LIHC, where fine pearlite with smaller pearlite block size and lower interlamellar spacing formed instead. Therefore, the abrupt change of microstructure and mechanical properties in the HAZ could be avoided by post-LIHC, and the hardness, strength and toughness of the rails can be improved significantly. The post-LIHC technology shows the potentiality to hardface and repair the full-scale rail.
关键词： Martensite,Microhardness distribution,Toughness,Laser-induction hybrid cladding (LIHC),Full-scale rail,Strength
更新于2025-11-28 14:24:20
-
Effect of thermal stress induced by femtosecond laser on fracture toughness of fine-grained alumina
摘要： The ultra-sharp V-notch with tip radius smaller than 0.5 μm was cut by femtosecond laser on the fine-grained alumina ceramic bars to measure the fracture toughness by single-edge V-notched beam (SEVNB) method. In order to relieve the effect of thermal stresses induced by laser on fracture toughness testing, the samples with V-notch were annealed before measurement. The morphologies of the notch tip were analyzed by SEM and micro-Raman spectra. Results reveal that the fracture toughness value of this fine-grained alumina with thermal stresses on the V-notch is equal to that after annealing, and the effect of thermal stresses induced by laser on the fracture toughness can be ignored.
关键词： SEVNB,Fracture toughness,Laser processing,Thermal stress,Alumina
更新于2025-11-21 11:18:25
-
Reinforcing effect of amine-functionalized and carboxylated porous graphene on toughness, thermal stability, and electrical conductivity of epoxy-based nanocomposites
摘要： Epoxy-based nanocomposites reinforced with nonfunctionalized porous graphene (NPG), carboxylated porous graphene (CNPG), and amine-functionalized porous graphene (ANPG) were investigated with regard to mechanical properties, thermal stability, and electrical conductivity. Nanomaterials were added to the epoxy matrix in varying contents of 0.5, 1, and 2 wt %. Generally, mechanical properties were improved as a result of introducing nanomaterials into the epoxy resin. However, the amelioration of toughness was only observed in functionalized NPGs/epoxy nanocomposites. Field emission scanning electron microscopy images showed that functionalized nanomaterials induced a rougher fracture surface compared to the neat epoxy. Dynamic mechanical analysis along with differential scanning calorimetry confirmed an increment in the glass-transition temperature (Tg) of the reinforced nanocomposites. Also, they proved that functionalization made the epoxy network tougher and more flexible. The electrical conductivity and thermal stability of the epoxy resin were also improved when loaded with nanomaterials.
关键词： toughness,electrical properties,thermal properties,nanocomposites
更新于2025-09-23 15:23:52
-
Electric field-induced toughening in GaN piezoelectric semiconductor ceramics
摘要： In this paper, the effect of an applied electric field on fracture toughness of polarized GaN piezoelectric semiconductor ceramics was studied by using experimental and numerical methods. The results show that fracture toughness increases by 22% under a field intensity of 0.83 kV cm?1, and with further increase of the electrical filed, fracture toughness remains unchanged. This is completely different from the fracture characteristics of traditional piezoelectric ceramics that is thought to decrease with an applied electric field. The reason for such a difference is attributed to the redistribution of free electrons. It is expected that this finding will be instructive to the reliability design of piezoelectric semiconductor structures and devices.
关键词： GaN,Electric field,Fracture toughness,Piezoelectric semiconductor ceramics,Toughening
更新于2025-09-23 15:23:52
-
Localized Deformation and Fracture Behaviors in InP Single Crystals by Indentation
摘要： The indentation-induced deformation mechanisms in InP(100) single crystals were investigated by using nanoindentation and cross-sectional transmission electron microscopy (XTEM) techniques. The results indicated that there were multiple “pop-in” events randomly distributed in the loading curves, which were conceived to arise primarily from the dislocation nucleation and propagation activities. An energetic estimation on the number of nanoindentation-induced dislocations associated with pop-in effects is discussed. Furthermore, the fracture patterns were performed by Vickers indentation. The fracture toughness and the fracture energy of InP(100) single crystals were calculated to be around 1.2 MPa·m1/2 and 14.1 J/m2, respectively.
关键词： InP(100) single crystal,nanoindentation,fracture toughness,transmission electron microscopy,Pop-in
更新于2025-09-23 15:23:52
-
Elasticity, Hardness, and Fracture Toughness of Sodium Aluminoborosilicate Glasses
摘要： Due to an increasing demand for oxide glasses with a better mechanical performance, there is a need to improve our understanding of the composition-structure-mechanical property relations in these brittle materials. At present, some properties such as Young’s modulus can to a large extent be predicted based on the chemical composition, while others – in particular fracture-related properties – are typically optimized based on a trial-and-error approach. In this work, we study the mechanical properties of a series of twenty glasses in the quartenary Na2O-Al2O3-B2O3-SiO2 system with fixed soda content, thus accessing different structural domains. Ultrasonic echography is used to determine the elastic moduli and Poisson’s ratio, while Vickers indentation is used to determine hardness. Furthermore, the single-edge precracked beam (SEPB) method is used to estimate the fracture toughness (KIc) for some compositions of interest. The compositional evolutions of Vickers hardness and Young’s modulus are in good agreement with those predicted from models based on bond constraint density and strength. Although there is a larger deviation, the overall compositional trend in KIc can also be predicted by a model based on the strength of the bonds assumed to be involved in the fracture process.
关键词： Vickers hardness,fracture toughness,glass properties,Elastic moduli,crack path
更新于2025-09-23 15:22:29
-
Transparent and Flexible Electronics Assembled with Metallic Nanowire-Layered Non-drying Glycerogel
摘要： There has been increasing demand for transparent and mechanically durable electrical conductors for their uses in wearable electronic devices. It is common to layer metallic nanowires on transparent but stiff polydimethylsiloxane (PDMS) or stretchable but opaque EcoflexTM-based substrates. Here, we hypothesized that layering metallic nanowires on a stretchable and hygroscopic gel would allow us to assemble a transparent, stretchable, and durable conductor. The hygroscopic property of the gel was attained by partially replacing water in the pre-formed polyacrylamide hydrogel with glycerol. The resulting gel, denoted as a glycerogel, could remain hydrated for over 6 months in air by taking up water molecules from the air. The glycerogel was tailored to be stretchable up to 8 times its original length by tuning the amount of cross-linker and acrylamide. The resulting glycerogel allowed for deposition of wavy silver nanowires using the pre-strain method up to 400 % pre-strain, without causing kinks and interfacial cracks often found with nanowires layered onto PDMS. With a pre-strain of 100%, the resulting nanowire-gel conductor exhibited optical transparency (85%) and electrical conductivity (17.1 ohm/sq) even after 5,000 cycles of deformation. The results of this study would broadly be useful to improve the performance of the next generation of flexible electronic devices.
关键词： glycerol,toughness,hydration,stretchable hydrogel,flexible electronics
更新于2025-09-23 15:21:01
-
Increasing Fracture Toughness and Transmittance of Transparent Ceramics using Functional Low-Thermal Expansion Coatings
摘要： Transparent polycrystalline ceramics have the potential to enable applications no other materials can, but to do so their strength and toughness must be improved. However, surface strengthening treatments like those used for glasses have so far remained elusive. Here for the first time, we report on engineering unprecedented surface compression, of the magnitude achieved for ion-exchange strengthened glasses (~750 MPa) in transparent ceramics. This was achieved by applying functional, low thermal-expansion yttria coatings onto yttria-stabilized zirconia substrates and thermally treating. In some instances, the treatment more than doubled the fracture toughness while simultaneously increasing light transmittance.
关键词： surface compression,transparent ceramics,fracture toughness,thermal-expansion mismatch,yttria coatings
更新于2025-09-23 15:21:01
-
Laser-arc hybrid welding of 12- and 15-mm thick structural steel
摘要： High-power lasers are very effective in welding of plates thicker than 10 mm due to the keyhole mode. High-power intensity generates a vapor-filled cavity which provides substantial penetration depth. Due to the narrow and deep weld geometry, there is susceptibility to high hardness and weld defects. Imperfections occur due to keyhole instability. A 16-kW disk laser was used for single-pass welding of 12- to 15-mm thick plates in a butt joint configuration. Root humping was the main imperfection and persisted within a wide range of process parameters. Added arc source to the laser beam process may cause increased root humping and sagging due to accelerated melt flow. Humping was mitigated by balancing certain arc and other process parameters. It was also found that lower welding speeds (< 1.2 m/min) combined with lower laser beam power (< 13 kW) can be more positive for suppression of humping. Machined edges provided more consistent root quality and integrity compared with plasma cut welded specimens. Higher heat input (> 0.80 kJ/mm) welds provided hardness level below 325 HV. The welded joints had good Charpy toughness at ? 50 °C (> 50 J) and high tensile strength.
关键词： Mechanical properties,Toughness,Thick steel,Hybrid welding,High strength steel,Laser welding
更新于2025-09-23 15:21:01
-
An insight into microstructural heterogeneities formation between weld subregions of laser welded copper to stainless steel joints
摘要： The effect of laser beam welding (LBW) process on the microstructure?mechanical property relationship of a dissimilar weld between the copper (Cu) and stainless steel (SS) was investigated. Backscattered electron (BSE) based scanning electron microscopy (SEM) imaging was used to characterize the highly heterogeneous microstructural features across the LBW (Cu?SS) weld. The BSE analysis thoroughly evidenced the complex microstructures produced at dissimilar weld interfaces and fusion zone along with the compositional information. Widely different grain growths from coarse columnar grains to equiaxed ultrafine grains were also evident along the Cu?weld interface. A high-resolution electron backscattered diffraction (EBSD) analysis confirmed the existence of the grain refinement mechanism at the Cu?weld interface. Both tensile and impact properties of the dissimilar weld were found to be closely aligned with the property of Cu base metal. Microhardness gradients were spatially evident in the non-homogeneous material composition zones such as fusion zone and the Cu?weld interface regions. The heterogeneous nucleation spots across the weld sub-regions were clearly identified and interlinked with their microhardness measurements for a holistic understanding of structure?property relationships of the local weld sub-regions. The findings were effectively correlated to achieve an insight into the local microstructural gradients across the weld.
关键词： impact toughness,laser beam welding,stainless steel,microstructural characterization,copper,tensile property
更新于2025-09-23 15:19:57