- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Influence of Laser Power on Grain Size and Tensile Strength of 5A90 Al–Li Alloy T-joint Fabricated by Dual Laser-Beam Bilateral Synchronous Welding
摘要： Dual laser-beam bilateral synchronous welding is introduced to produce the 2.5 mm thick 5A90 Al–Li alloy T-joint. The grain morphology and grain size of weld metal (WM) in the T-joint are analyzed and calculated. The tensile experiment, scanning electron microscopy and energy disperse spectroscopy are respectively employed to study the tensile strength, fracture morphology and chemical composition of the T-joint. The results reveal that when the laser power is increased from 2500 to 3000 W, the grain sizes of fine-grained layers and columnar dendrites near the fusion line are significantly reduced. Conversely, that of equiaxed dendrites at the WM center is not sensitive to the variety of laser power. Moreover, the degree of elemental segregation in WM near the fusion line is also aggravated with the increasing of the laser power. The tensile strength of the T-joint with the laser power of 2500 W is significantly higher than that with the laser power of 3000 W. The tensile fracture locations are occurred in the weld toe with obvious pores, shear dimples and tear ridges, which are the typical characteristics of ductile fracture. Besides, the chemical compositions of the second phase particles in the WM are more sensitive to than the variation of laser power compared with that of the matrix.
关键词： T-joint,5A90 Al–Li alloy,Tensile strength,DLBSW,Gain size
更新于2025-09-16 10:30:52
-
[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Generation of MV/cm longitudinal terahertz electric fields from relativistic laser-solid interactions
摘要： We report on the generation and detection of longitudinal terahertz (THz) transient, with field strength of 1.5 MV/cm [1], at the focus of a radially polarized high-power terahertz beam generated at the rear surface of a thin metal foil irradiated by multi-terawatt laser pulse [2]. An f/1.5 off-axis parabolic mirror was used to focus the collimated THz beam. In addition to the longitudinal field, a transverse field, albeit off-axis, with amplitude in excess of 3 MV/cm was also measured.
关键词： multi-terawatt laser pulse,field strength,high-power terahertz beam,off-axis parabolic mirror,longitudinal terahertz
更新于2025-09-16 10:30:52
-
Intense red emission on dilute Mn-doped CaYAlO4-based ceramics obtained by laser floating zone
摘要： The laser floating zone (LFZ) technique was used to produce polycrystalline fibers composed by P21/c monoclinic Y4Al2O9 (YAM) and P?421m tetragonal CaYAl3O7 (CYAM) phases embedded into I4/mmm tetragonal CaYAlO4 matrix. The scanning electron microscopy and X-ray diffraction patterns put in evidence the strong effect of growth rate on the microstructural and phases’ evolution. Besides the microstructural and structural analysis, complementary optical techniques as photoluminescence (PL), PL excitation (PLE), and lifetime measurements were used to characterize the produced fibers. The nonintentionally doped fibers were shown to exhibit an intense deep red emission likely due to Mn4+ trace impurities. From the PLE measurements, average crystal field strength was estimated with Dq/B ~ 2.94. Temperature-dependent PL measurements revealed that the red luminescence is due to the overlap of transitions from the almost electronic degenerate 2E and 4T2 excited states to the 4A2 ground state. The emission from the two excited states arises due to the breakdown of the adiabatic approximation. The overall luminescence intensity of the red emission was found to decrease from 11 K to RT, and the internal quantum efficiency, estimated from the ratio of the integrated luminescence at high and low temperatures, was found to be 60%. Time-resolved spectroscopy indicates a single decay time of ca. 2.0 ms at room temperature, corresponding to the spin and parity forbidden 2E → 4A2 transition.
关键词： Laser floating zone,Crystal field strength,Polycrystalline fibers,Mn4+ trace impurities,Red emission
更新于2025-09-16 10:30:52
-
[IEEE 2019 International Wafer Level Packaging Conference (IWLPC) - San Jose, CA, USA (2019.10.22-2019.10.24)] 2019 International Wafer Level Packaging Conference (IWLPC) - Thermal Laser Seperation with Deep Scribe for Silicon Wafer Dicing
摘要： TLS-Dicing (Thermal Laser Separation) is a unique technology for separating wafers into single chips in semiconductor back end processing. TLS-Dicing uses thermally induced mechanical stress to separate brittle semiconductor materials, like silicon (Si) and silicon carbide (SiC) wafers. TLS is a two-step TLS-Dicing method consisting of scribing and cleaving. The scribing is used to create a starting point of the second step – the cleaving step. A continuous wave laser in combination with water spray cooling generates a thermal distribution. This leads to a mechanical stress capable to guide one defined crack along the dicing street which leads to the separation of the material. This work investigates a new scribing method – the Deep Scribe – in detail. While using Deep Scribe a pulsed laser beam of near infrared wavelength is focused with an objective into the silicon. This generates a line of sub- surface material modification. By using this scribe technique no particles occur at the surface. Additionally, straightness and the bending strength of separated silicon chips can be improved in comparison with state of the art dicing technologies. In this presentation, we will discuss the latest developments in Deep Scribe TLS with focus on the physical effects of the interaction between laser beam and material, as well the requirements for generation of a Deep Scribe. We will investigate the influence of adjusting parameters such as focus position, duration of laser pulse and laser power, on position and size of the modified area. We will also study the effects of thermal laser separation with Deep Scribe on bending strength of diced chips, a crucial parameter for wafer thinning applications. For comparison, similar wafers were cut with current state-of-the-art mechanical blade dicing.
关键词： Dicing,Silicon,Thermal Laser Separation,Bending Strength
更新于2025-09-16 10:30:52
-
Influence of Powder Condition on Surface Properties of Cold-Resistant High-Strength Steel Produced by Direct Laser Deposition Method
摘要： Direct laser deposition (DLD) allows creating parts of complex shapes and configurations in a single process step without using of additional equipment. Such technologies are required in the shipbuilding industry, aircrafts, gas turbines, mechanical engineering etc., where it is necessary to manufacture large-sized and complex products that have a long technological cycle for production using classical technologies. DLD makes it possible to produce parts of various alloys with mechanical characteristics at the level of the wrought alloys. The publication is described direct laser deposition of high-strength cold-resistant steels results. Besides mechanical properties of material, the exploitation properties of the structure are also significantly important. Results of corrosion, abrasive-corrosion and tribotechnical tests are shown.
关键词： corrosion resistance,high-strength steel,abrasive-corrosion resistance,Direct laser deposition,cold-resistant steel,initial powder condition,wear resistance
更新于2025-09-16 10:30:52
-
Parameter Optimization for Laser Welding of High Strength Dissimilar Materials
摘要： Dissimilar joining of high strength tensile steels are joined using laser beam welding. The selection of the welding conditions for joining of dissimilar materials is highly required to satisfy the quality of the joints. In the present investigation, optimization technique were used to determine the optimal welding conditions. Initially welding conditions were optimized for weld geometry and formation of different zones in the weldment. The metallurgical and mechanical properties of the welds are greatly influenced by the geometry of the welds. The surface response methodology design is carried out for the experimental design by the development of regression equations. Analysis of variance (ANOVA) was used to check the validity of the model. The output of the welding conditions were compared with the predicted values to identify the accuracy of the model. The obtained results from response surface methodology were compared with the experimental results and validated.
关键词： Optimization,Fusion zone,Mechanical properties,Laser welding,Welding parameters,High strength steel,Bead geometry
更新于2025-09-16 10:30:52
-
Three-pass laser welding of Ti alloy-stainless steel using Nb and Ni interlayers
摘要： Nb:YAG laser welding of TC4 titanium (Ti) alloy and 301 L stainless steel (SS) were carried out through interlayers Nb and Ni. The laser beam was concentrated at the Ti alloy-Nb interface, Nb-Ni interface and Ni-SS interface, respectively, to ensure that whole Nb and Ni interlayer was not melted. Three-pass welding was employed, which involves the creation of a joint with three welding zones separated by the remaining unmelted Nb and Ni. Interlayer Nb and Ni were employed to prevent the formation of Ti-Fe intermetallics and improve the microstructure and the properties of the Ti alloy-SS joint. The joint fractured at the welding zone of the Nb-Ni interface with the tensile strength of 269 MPa.
关键词： Interlayer,Tensile strength,Microstructure,Welding
更新于2025-09-16 10:30:52
-
Microstructure and Tensile Property of the Joint of Laser-MIG Hybrid Welded Thick-Section TC4 Alloy
摘要： In this paper, thick-section TC4 alloy was welded to itself by laser-MIG hybrid (LAMIG) welding. The microstructure of the welded joints was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results revealed that α’ and β phases were formed in the weld seam. The effects of heat input (E) on the microstructure and tensile strength of the joints were investigated. With the increase of heat input, the residence time of platelet α’ martensite in the high-temperature phase changing zone became longer and the thickness of platelet α’ martensite increased. Furthermore, the β thickness became large, and tangling dislocations were found to exist in platelet α’. In addition, the increasing heat input could cause a decrease in the tensile strength. The failed dimple pattern experienced a change from equiaxed to tearing, which was harmful to the property of the joint.
关键词： α’ martensite,titanium welding,strength,microstructural analysis
更新于2025-09-16 10:30:52
-
Polarizability of germanium quantum dots with spatially separated electrons and holes in Ge/Si heterostructures
摘要： In the framework of dipole approximation, it is shown that the quantities (the oscillator strengths of transitions, the dipole moments for transitions, and the polarizability) describing optical absorption on surface exciton states with spatially separated electrons and holes (the hole moves in the germanium quantum dot and the electron is localised over the spherical interface of the silicon quantum dot matrix) assume giant values considerably exceeding the typical values of the corresponding quantities for semiconductors under the action of low-intensity light.
关键词： transition dipole moments,polarizability,oscillator strength,Spatially indirect excitons,quantum dots,polarization interaction,Coulomb interaction
更新于2025-09-16 10:30:52
-
Oscillator strength and carrier dynamics in type I and inverted type I spherical core/ shell nanostructures under external laser field
摘要： For the first time, the effect of laser on the donor impurity states in spherical nano core/ shell systems is examined theoretically by variation technique. In this work, a step like laser dressed confinement potential is employed to evolve the donor dynamics in two different spherical core/ shell quantum structures namely (a) Type I GaAs/ Al0.3Ga0.7As core shell nanostructure (CSN) and (b) Inverted Type I Al0.3Ga0.7As/ GaAs CSN. Donor binding energy (BE) is calculated for various laser dressing parameter (α0) for various impurity locations (Ri) by varying the dimensions of the systems. Effect of laser on sub-level energy (E0), oscillator strength (P10), transition energy (E10) and the magnitude of dipole matrix element (|M10|) of the systems are also determined. The diverse behavior of type I and inverted type I CSNs are analyzed. It is witnessed that in type I the carrier is highly confined whereas inverted type I favors tunneling. This study will help in understanding the influence of laser field on donor impurity in CSNs and its application towards optical devices.
关键词： Type I core/shell,Laser field,Donor Binding,Oscillator Strength,Inverted Type I core/shell
更新于2025-09-16 10:30:52