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Microstructure and properties of 24CrNiMoY alloy steel prepared by direct laser deposited under different preheating temperatures
摘要： The direct laser deposition (DLD) process, evolution mechanism between preheating temperature and structure are visually described in this graph. Fig. 1(a) displays the DLD process design for preheating the substrate, the main heat transfer method is heat conduction. Fig. 1(b) shows the formation mechanism of the pores in the DLD process, it can be seen that the pores in the sample mainly underwent three processes of formation, floating, and growth. Fig. 1(c) exhibits the evolution mechanism between the bainite structure and preheating temperature of 24CrNiMoY alloy steel, it can be deduced the microstructure of the sample changes from lath bainite (LB) to granular bainite (GB) with the rise of preheating temperature. The proper preheating temperature of 200℃ can effectively eliminate the crack, decrease the pores and significantly improve the structure and properties of the DLD 24CrNiMoY alloy steel.
关键词： Preheating,24CrNiMoY alloy steel,Bainite,Direct Laser Deposited,Mechanical properties
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Sunlight Concentration Properties of InAs/InAsSb Ultrahigh-Density Quantum-Dot Solar Cells
摘要： In this paper, a robotic cell rotation method based on the minimum rotation force is presented to adjust oocyte orientation in biological applications. In this method, the minimum rotation force, which can control the rotation angle (RA) of the oocyte quantitatively and generate minimum oocyte deformations, is derived through a force analysis on the oocyte in rotation. To exert this force on the oocyte, the moving trajectories (MT) of the injection micropipette (IM), are determined using mechanical properties of the oocytes. Further, by moving the IM along the designed MT, the rotation force control is achieved. To verify the feasibility of this method, a robotic rotation experiment for batch porcine oocytes are performed. Experimental results demonstrate that this system rotates the oocyte a10t an average speed of 28.6s/cell and with a success rate of 93.3%. More importantly, this method can generate much less oocyte deformations during cell rotation process compared with the manual method, while the average control error of RA in each step is only 1.2 (versus averagely 8.3 in manual operation), which demonstrates that our method can effectively reduce cell deformations and improve control accuracy of the RA.
关键词： micro-operation,force control,Cell mechanical properties,cell rotation
更新于2025-09-19 17:13:59
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POST WELD HEAT TREATMENT OF NiTinol SHAPE MEMORY ALLOY USING LASER POWER SOURCE
摘要： In this work, attempt is made to carry out post weld heat treatment (PWHT) on NiTinol samples using laser power source. Initially, 1 mm thick NiTinol sheets were welded in butt joint position using Ytterbium: Yttrium aluminum garnet (Yb: YAG) laser power source. Laser welding was carried out in continuous mode, and the quality of the weld was assessed with respect to phase transformation temperatures, microhardness, tensile strength, and corrosion resistance. To improve the quality of the welded samples, PWHT was done by passing a laser beam over the welded samples. It was found that PWHT had a significant effect on the phase transformation temperatures, microhardness, tensile strength and corrosion behavior of the welded NiTinol joints.
关键词： laser heat treatment,NiTinol,laser welding,mechanical properties,corrosion behavior
更新于2025-09-19 17:13:59
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Structural and mechanical characterization of carbon fibers grown by laser induced chemical vapor deposition at hyperbaric pressures
摘要： Laser induced chemical vapor deposition (LCVD) of freestanding carbon fibers from ethylene at hyperbaric pressures was investigated. Relationships between processing conditions, growth behavior, microstructure, and mechanical properties of the carbon fibers were established. It is found that the fiber growth rates are limited by surface reaction kinetics at low temperatures and limited by gas phase nucleation at high temperatures. At higher pressures and intermediate temperatures, growth becomes mass transport limited whereupon the fibers exhibit drastic changes in morphology and microstructure from a core-shell, smooth appearance to nodular formations. The tensile strengths of the carbon fibers grown by LCVD are generally poor due to the nature of graphitic carbon deposits. However, the Weibull modulus among the LCVD grown carbon fibers was found to be very high. Effects of processing conditions and microstructure on the fiber strengths are observed and discussed.
关键词： Microstructure,Hyperbaric pressures,Laser induced chemical vapor deposition,Carbon fibers,Mechanical properties
更新于2025-09-19 17:13:59
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Influence mechanism of process parameters on the interfacial characterization of selective laser melting 316L/CuSn10
摘要： Bimetallic structures can combine the performance of dissimilar metal materials to meet the multifunctional requirement in industrial solutions. In this paper, steel-bronze bimetallic structures were fabricated via self-developed multi-material selective laser melting (SLM) equipment. In order to investigate the influence of laser power, scanning speed, and hatching space on the interfacial characterization, three factors and five levels of orthogonal experiments were performed on twenty layers of CuSn10 tin bronze after forming the 316L stainless steel. Optical microscope (OM), large depth field microscope, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), tensile properties, electron backscattering diffraction (EBSD) and nanoindentation were used to characterize these bimetallic structures to validate the impact from process parameters. The large depth field microscope revealed protrusions at the steel/bronze interface, and its height increased and then decreased with increasing volumetric energy input. Besides, the generation of interfacial defects is related to the interfacial process parameters, and it is found that the types of defects are mainly classified as holes and cracks. Insufficient energy will cause cracks in the horizontal direction and then lead to bonding failure. Conversely, higher energy input will generate microcracks in the vertical direction. The defects near the interfacial region are the main factors affecting the ultimate strength of the bonding strength. As a result, the steel-bronze bimetallic structure displays optimal joint ultimate strength of 459.54±3.08 MPa with elongation of 5.23±0.65%, and minimum joint ultimate strength of 199.02±0.56 MPa with elongation of 1.70±0.22%. Their fracture morphology also exhibited gully-like and fan-shaped features, respectively. Additionally, the EBSD results show that there are fine grain regions appeared in the interfacial region, which helps increase the average nano-hardness of the interfacial region. This study provides a reference for the influence of process parameters on the interfacial characterization and mechanical properties of steel-bronze bimetallic parts prepared by selective laser melting.
关键词： Interfacial characterization,Mechanical properties,Selective laser melting,Bimetallic structure,Multi-material
更新于2025-09-19 17:13:59
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Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting
摘要： Selective laser melting (SLM) is emerging as a promising 3D printing method for orthopedic and dental applications. However, SLM-based Ti6Al4V components frequently exhibit high roughness values and partial surface defects. Laser polishing (LP) is a newly developed technology to improve the surface quality of metals. In this research, LP is applied to improve the surface ?nish of components. The results show that the laser beam can neatly ablate the aggregates of metallic globules and repair cracks and pores on the surface, resulting in a smooth surface with nanocomposites. Overall, the results indicate that using LP optimizes surface morphology to favor fatigue behavior and osteoblastic di?erentiation. These ?ndings provide foundational data to improve the surface roughness of a laser-polished implant and pave the way for optimized mechanical behavior and biocompatibility via the laser process.
关键词： laser polishing,additive manufacturing,biocompatibility,mechanical properties,surface roughness
更新于2025-09-19 17:13:59
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A highly adhesive flexible strain sensor based on ultra-violet adhesive filled by graphene and carbon black for wearable monitoring
摘要： Ensuring the accuracy of signal detection under repeated deformation is a challenge for ?exible sensor reported in recent years, and achieving reliable adhension between the sensor and substrate is a key factor. Here, this article reported a highly adhesive ?exible strain sensor based on ultra-violet adhesive ?lled by modi?ed graphene and carbon black for wearable monitoring. This strain sensor with a typical resistive behavior shows gauge factor calculated at 0～10% strain is 2.1. It exhibits short curing time (～1 h), fast response (～40 ms), excellent adhesive strength (4500 kPa), and adhesiveness to various bending surfaces. Furthermore, this strain sensor can be directly prepared on elastic columns and rubber gloves, and exhibits excellent performance in three-dimensional force detection and writing gesture recognition. The ability of adhesive conformability to arbitrary and complex surfaces shows that the strain sensor has broad application prospects in wearable devices.
关键词： Electrical properties,Smart materials,Adhesive joints,Mechanical properties,Nano composites
更新于2025-09-16 10:30:52
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Optimization of Process Parameters Using Surface Response Methodology for Laser Welding of Titanium Alloy
摘要： Laser beam welding input conditions are greatly influence the quality of the welded joints and they have significant role on the controlling of their strength and metallurgical properties. The metallurgical properties and weld bead geometry and mechanical properties of the joints determine the quality of the joints. In this study, the fusion zone width, penetration, width of the heat affected zone and strength of the titanium alloy welds were investigated using laser welding process. 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. In order to identify the significant parameters, student’s test is conducted. 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,Titanium alloy,Bead geometry
更新于2025-09-16 10:30:52
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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
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Effect of Process Parameters and Heat Input on Weld Bead Geometry of Laser Welded Titanium Ti-6Al-4V Alloy
摘要： Laser beam welding is one of the most favorable welding technique and its importance in industry is demanding due to higher welding speeds and lower dimensions and distortions in the welds. Moreover, its high strength to weld geometries and minimal heat affected zones makes favorable for various industrial applications. In the present study, laser welding of titanium alloy was investigated to observe the effects of parameters on the bead geometry and metallurgical properties. The laser power and welding speeds were varied to identify their impact on the formation of weld geometry. The width and depth of the fusion zone is varied with welding conditions. The finer grains identified in weld zone and the width of heat affected zone was significantly changes with laser welding power. The mechanical properties of the weld joint are controlled by obtaining optimum weld bead geometry and width of the head affected zone in the welds.
关键词： Heat input,Fusion zone,Microstructure,Mechanical properties,Laser welding,Microhardness,Weld bead geometry,Titanium alloy
更新于2025-09-16 10:30:52