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Laser beam welding of DP980 dual phase steel at high temperatures
摘要： Dual phase steels have been used in safety components for the automotive industry and represents a standard in terms of energy absorbing steel alloys. After welding, these components present a martensitic transformation in the fusion and heat-a?ected zones with an intrinsic brittleness. The current contribution presents a procedure where the DP980 steel sheet is kept at a given temperature during and after the laser weld in order to generate bainite instead of martensite. The results using an isothermal treatment at 527 °C shown a microstructure composed by grain boundary and bainitic ferrite and retained austenite with a constant hardness in the base material and heat-a?ected and fusion zones of 280 HV. The room temperature welds present hardness values between 320 and 500 HV. The high-temperature welds also shown a decrease in the maximum residual stress at the weld centerline by 1/3, with a consequential reduction in the warp of the joined component.
关键词： Heat treatment,Hardness testing,Laser beam welding,Dual phase steels
更新于2025-09-11 14:15:04
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Alteration of fracture toughness (KIC) following laser shock peening of silicon nitride ceramics
摘要： This work focuses on the development in laser shock peening (LSP) Si3N4 ceramics with a view to first observe the general effects namely; the topography, hardness, flaw size, plane strain fracture toughness (KIc). Firstly, an LSP surface treatment was conducted to establish a crack-free surface treatment. This also established a parametric window and elucidated the feasibility of treating a brittle material such as Si3N4 with a high intensity/pressure surface treatment such as LSP. Upon comparing the as-received surface with the LSPned surface elucidated a natural increase in surface roughness from an average of 1.73μm to 4.79μm. This indicated some level of material removal. In addition, a decrease in hardness was found by 4.5% and an increase in the KIc by over 21.5% through a possible induction of plasticity within the Si3N4. The microstructure of the Si3N4 also showed considerable changes after LSP surface treatment and a possible α-beta transformation were introduced which indicated surface strengthening. The work undertaken herein have shown that with further refinement of the LSP parameters, this type of laser treatment could be beneficial for strengthening advanced ceramics, particularly, as the process offers a mechanism for enhancement in fracture toughness. An alteration of such an important property of a Si3N4 would open new avenues for its applications particularly where metals and alloys fail.
关键词： hardness,surface treatment,Laser shock peening,Si3N4 ceramics,fracture toughness
更新于2025-09-11 14:15:04
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Characteristics of Diamond-Like Carbon Films Fabricated by Using a Filtered Vacuum Arc System for Dye-Sensitized Solar Cells
摘要： Dye-sensitized solar cells (DSSC) based on diamond-like carbon (DLC) anti-re?ection coating (ARC) thin ?lms are investigated. The DLC ?lm was proposed to improve the cell performance of DSSC devices. In this work, the DLC ?lms were fabricated by using the FVA (?ltered vacuum arc) method, the structural, optical, and physical properties of the fabricated DLC ?lms with various ?lm thicknesses were experimentally investigated. All DLC ?lms showed smoother and more uniform surfaces with increasing ?lm thickness. Furthermore, the values of rms surface roughness, friction coe?cient, the refractive index, and the absorption coe?cient increased with increasing ?lm thickness, the hardness and the elastic modulus of the DLC ?lms were improved. These results are associated with the increased sp3 contents in the amorphous carbon ?lm due to the e?ects of the energetic ion bombardment during ?lm deposition.
关键词： DLC,Filtered vacuum arc (FVA),Hardness,Anti-re?ection,Friction coe?cient,Power conversion e?ciency
更新于2025-09-11 14:15:04
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Study on magnetic abrasive finishing of AlSi10Mg alloy prepared by selective laser melting
摘要： Selective laser melting (SLM) technology is playing an increasingly important role in today’s manufacturing industry. However, the surface quality of SLM samples is relatively poor and cannot be directly applied to industrial production. Therefore, this paper focuses on the post-treatment process of SLM AlSi10Mg alloy. First, the rough machining is performed by a grinding process (GP), and then, the magnetic abrasive finishing (MAF) is used for finish machining. The experiment results show that the combination of GP and MAF can effectively reduce the surface roughness and improve the surface quality of SLM AlSi10Mg alloy. The GP reduced the surface roughness to drop from 7 μm (after SLM forming) to about 0.6 μm, and the rough surface with defects such as spheroids and pits evolved into the fine surface with scratches and pores. The MAF reduced the surface roughness to a minimum of 0.155 μm, which resulted in excellent surface morphology. The surface hardness after the GP was higher, and the MAF reduced the hardness of the GP surface.
关键词： Grinding process,Hardness,AlSi10Mg alloy,Selective laser melting,Surface roughness,Magnetic abrasive finishing
更新于2025-09-11 14:15:04
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Effect of Pyrolysis Temperature on the Mechanical Response in Partially Pyrolysed Polysiloxanes
摘要： The pyrolysis process of polysiloxane resin conducted in the temperature range 400 – 700 °C results in hybrid materials owning some polymeric (thermosetting) behaviour. A certain level of elastic recovery and/or viscoelastic flow showed at various steps of pyrolytic transformation was monitored using the instrumented Vickers hardness method. Determined indentation force-indentation depth curves reflect the mechanical response and the level of the transformation; however, the relaxation behaviour is not covered by this method fully. An extensive indentation relaxation was revealed in the material partially pyrolysed at 400 °C, about 16 % and 8 % when the HV 0.1 and the HV 0.2 loading were applied, respectively. Materials pyrolysed from 500 to 650 °C which exhibited the indentation relaxation below 1 % and the mostly elastic response on the loading were observed. Above the pyrolysis temperature of 600 °C a rapid onset of mechanical properties, namely indentation elastic modulus and hardness, was observed. The short-term indentation relaxation was evaluated via the indentation force relaxation method in the regime of constant indentation depth obtained at the moment of reaching an initial force of 0.981 N or 1.962 N. The obtained indentation force relaxation curves were analysed on the basis of a logarithmic function. The significant effect of the pyrolysis temperature as well as the influence of loaded volume was described.
关键词： polysiloxane,relaxation,partial pyrolysis,instrumented hardness
更新于2025-09-10 09:29:36
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The Effects of Heat Treatment on Microstructure and Mechanical Properties of Tribaloy 400 Coatings Deposited by Laser Cladding
摘要： The effects of heat treatment on the microstructure, microhardness, nanohardness and wear resistance of Tribaloy 400 coatings prepared by laser cladding on 304 stainless steel were studied in this paper. The results show that the microstructures of Tribaloy 400 laser cladding layer are cobalt matrix dendrites and eutectic structure. After the heat treatment at 1250 °C for 1 h, the eutectic structure disappears and the strip-like Laves phase is formed on the Co matrix. Meanwhile, the hardness is obviously improved. After the heat treatment at 1250 °C for 1 h and then 900 °C for 4 h, a small amount of e-Co appears, the strip-like Laves phases become coarser and blunter, and some of the strip structures combine together to form blocky structures, and the hardness is decreased. The wear resistance of the samples at 600 °C is better than that at RT since the hardness of the Laves phase increases with the rise in temperature.
关键词： Laves phase,wear resistance,hardness,heat treatment,Tribaloy alloy
更新于2025-09-10 09:29:36
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Formation and properties of a Zr-based amorphous coating by laser cladding
摘要： (Zr0.53Al0.1Ni0.05Cu0.3Ti0.02)99Y1 (at%) coating with amorphous layer of about 180 lm thick was prepared on a steel substrate by using laser cladding method. The coating is compact and shows good metallurgical bonding with substrate. The microstructure, microhardness and corrosion behavior along the depth from the coating surface to the substrate were investigated. It is found that a gradient structure consisted of amorphous surface layer, amorphous–crystalline transitional layer and substrate is formed after the laser cladding. The microhardness and corrosion behavior exhibit variation with the microstructural evolution at different depths from the coating surface. The microhardness and corrosion resistance in 3.5 wt% NaCl solution of the amorphous surface layer are comparable to those of the as-cast Zr-based BMG with the same composition, and higher than those of the steel substrate.
关键词： Laser cladding,Hardness,Corrosion resistance,Amorphous coating,Microstructure
更新于2025-09-10 09:29:36
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Simulation and Experimental Study on Properties of Ag/SnO <sub/>2</sub> Contact Materials Doped with Different Ratios of Ce
摘要： SnO2 in the Ag/SnO2 contact material is a kind of high hardness and almost insulated wide bandgap semiconductor material. In the process of use, the contact resistance is larger and the temperature rise is higher, which reduces the reliability of contacts and shortens the electrical life. In order to improve the properties of Ag/SnO2 contact materials, based on the first principle of density functional theory, this paper presents a method of doping SnO2 with the calculation of different proportions of rare earth Ce electrical and mechanical properties. The results of energy band, density of state, and elastic constant show that when the doping ratio of Ce is 0.125, the electron mobility is the highest, the conductivity is the best; the hardness decreases, and the universal elastic anisotropy index is the smallest. Finally, in the experiment, SnO2 powders with different doping ratios are prepared by the sol-gel method, and Ag/SnO2 contacts with different doping proportions are prepared by powder metallurgy. Arc energy, contact resistance, and hardness are measured; scanning electron microscopy was used to observe and analyze the surface morphology. The final simulation and experimental results are well matched.
关键词： doping,contact materials,rare earth Ce,conductivity,hardness,Ag/SnO2
更新于2025-09-10 09:29:36
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Growth and characterization of third-order nonlinear optical lithium hydrogen maleate dihydrate single-crystal
摘要： A third-order nonlinear optical crystal of lithium hydrogen maleate dihydrate (LHMD) is grown by the process of slow evaporation at room-temperature. The LHMD crystal system is orthorhombic and is a member of P space group. Using FTIR spectral investigation, the presence of main functional groups in LHMD crystal is identified. The optical behavior of the crystal is determined by UV-Visible spectroscopy. The bandgap energy of the LHMD crystal is calculated to be 3.4 eV. By Vickers microhardness measurements, the mechanical behavior has been assessed. The melting point of LHMD is determined by TG-DTA analysis. The defects present in the LHMD crystal are studied by dielectric loss and dielectric constant. SHG studies are performed for the LHMD crystal by Kurtz and Perry method. The third-order nonlinear characteristics of the LHMD crystal are analyzed by Z-scan technique. The laser damage threshold (LDT) study is carried out to verify the suitability of the crystal for laser applications.
关键词： LHMD,optical studies,TGA,third-order nonlinear studies,hardness
更新于2025-09-09 09:28:46
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Synthesis of Transparent Nano-Ceramics under Ultra-High Pressure; 透明ナノセラミックスの超高圧合成;
摘要： Various transparent nano-ceramics have been synthesized using direct conversion from bulk glass starting materials under pressures higher than ～10 GPa and at high temperatures in Kawai-type Multi-anvil Apparatus (KMA). Rapid nucleation followed by slow crystal/grain growth is the key to synthesize such nano-ceramics at the ultra-high pressure regime. Thus synthesized novel ceramics have interesting features, such as higher hardness and lower thermal conductivity relative to those of the corresponding single crystals, in addition to their high optical transparencies, which may be useful for some scientific and industrial applications.
关键词： transparent nano-ceramics,KMA,ultra-high pressure,polycrystalline material,hardness
更新于2025-09-09 09:28:46