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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
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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
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Fatigue behaviour of a laser beam welded CoCrFeNiMn-type high entropy alloy
摘要： Laser beam welding was used to produce butt joints from the CoCrFeNiMn-type high entropy alloy. The alloy in the initial condition had an fcc single-phase coarse-grained structure. Laser welding resulted in the M7C3-type carbides precipitation in the fcc matrix. The carbide particles precipitation resulted in a considerable increase in microhardness from 150 HV 0.5 for the as-sintered condition to 205 HV 0.5 in the fusion zone. Laser beam welding had a negligible effect on both static mechanical properties and fatigue behaviour of the alloy. The endurance limit of either type of specimens (i.e. with and without welding seam) was 200 MPa. Fracture of all specimens with the laser beam welded seams occurred in the base material area during both tensile and fatigue testing. Weak effect of welding on static/fatigue behaviour of the alloy can be attributed to the higher hardness of the fusion zone, resulting in strain localization in the base material area. An increase in load resulted in activation of secondary slip systems and formation of deformation twins in fatigue specimens.
关键词： Fatigue,Tensile strength,Microstructure,Laser beam welding,High entropy alloy
更新于2025-09-16 10:30:52
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Effect of adherend deflection on lap-shear tensile strength of laser-treated adhesive-bonded joints
摘要： Laser surface treatment was used as a surface preparation method for adherend prior to adhesive bonding, which significantly improved the fracture mode from mixed to cohesive and consequently increased the lap-shear tensile strength by 27.5% and 28.2% for aluminum alloys AA7075 and AA6022 adhesive-bonded joints, respectively. Nevertheless, the laser-treated AA7075 joint exhibited a ~14% higher strength compared to laser-treated AA6022 joint although both joints showed cohesive fracture modes, which was attributed to smaller adherend deflection of laser-treated AA7075 joint than that of laser-treated AA6022 joint. Digital image correlation technique was applied to monitoring the deflections of laser-treated AA7075 and AA6022 joints during lap-shear tensile testing, and the stress analysis of adhesive-bonded lap-shear joints was conducted by finite element simulation. It was found that the deflection angle of the laser-treated AA6022 joint reached to 6.1° at the peak tensile load and was ~69% larger than that of laser-treated AA7075 joint (i.e. 3.6°), which resulted in a mixed stress state with higher peel stress (i.e. ~8 MPa) on edges of adhesive bonding region and consequently led to a premature fracture due to the low peel resistance of adhesive-bonded joints. Furthermore, the effect of decreased adherend deflection on lap-shear tensile strength was investigated, and a linear increase of lap-shear tensile strength was found with the decrease of deflection angle for adhesive-bonded joints showing cohesive fracture modes.
关键词： finite element stress analysis (C),lap-shear tensile strength (C),laser surface treatment (B),aluminum alloys (B),adherend deflection
更新于2025-09-12 10:27:22
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Laser additive manufacturing of bimetallic structure from Ti-6Al-4V to Ti-48Al-2Cr-2Nb via vanadium interlayer
摘要： As a potential candidate material, Ti6Al4V (TC4) / Ti48Al2Cr2Nb (TiAl) bimetallic structure (BS) material has a good development prospects in the field of aerospace engineering, and has a broad application prospects for the integrated manufacture of aero-engine turbine blades (TiAl) and turbine disks (TC4). However, via the direct bonding of TC4/TiAl BS, it is easy to produce brittle intermetallic compounds which increases the crack sensitivity. Therefore, to a certain extent, the application of TC4/TiAl BS is limited. In this study, we use laser additive manufacturing (LAM) technology to prepare the TC4 / TiAl BS via a V interlayer, which further limits the formation of a brittle phase. The experimental results show that the V interlayer can effectively limit the formation of the brittle phase (Ti3Al), which reduces the crack sensitivity of the formed parts, and forms a good metallurgical joint at the TC4/TiAl BS interfaces. Results of room temperature tensile tests reveal that the tensile strength and elongation of the BS specimens are ~476 MPa, and ~2.8% respectively , which means that the strength of the joint exceeded that of the deposited TiAl alloy without the V interlayer.
关键词： Microstructure,Brittle phases,Ti/TiAl bimetallic structure,Tensile strength,Interfaces,Laser additive manufacturing
更新于2025-09-12 10:27:22
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Laser additive manufacturing of TA15 - Inconel 718 bimetallic structure via Nb/Cu multi-interlayer
摘要： High quality fabricating of the bimetallic structure of TA15 and Inconel 718 (IN718) is widely used in the aerospace ?led. In this study, we have used laser additive manufacturing (LAM) technology to fabricate the bimetallic structure and to prevent the formation of brittle phases via Nb/Cu multi-interlayer. The results of this study showed that Nb/Cu multi-interlayer was very e?ective in preventing the generation of brittle Ti–Ni and Ti–Cu phases. The good metallurgical bonds were presented at these interfaces between TA15 and IN718. Mechanical properties of the bimetallic structure revealed that the tensile strength reached that of the weakest metal, Cu.
关键词： Tensile strength,Microstructure,Laser additive manufacturing,Interfaces,Interlayer
更新于2025-09-12 10:27:22
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Near infrared spectroscopic measurement of strain in rocks
摘要： The measurement of strain is a fundamental and widely studied parameter in engineering, rock mechanics, construction and materials testing. Contact sensors often used in these fields require contact with the target surface throughout the duration of a strain event. Non-contact methods typically require that that the measurement surface is prepared and often coated prior to testing. This paper considers the potential application of near infrared spectroscopy as a non-contact technique for the measurement of strain on natural surfaces. Excellent correlation was found between surface measurements of visible-NIR spectra and longitudinal strain taken during indirect Brazilian Disc Test for samples of sandstone, marble and basalt.
关键词： rock,indirect tensile strength,Strain measurement,near infrared spectroscopy
更新于2025-09-11 14:15:04
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Performance analysis of fiber reinforced piezoelectric lead zirconate titanate/poly(vinylidene fluoride) composites
摘要： In this paper, the PZT/PVDF composites were prepared by hot-pressing method. The effects of different PZT volume fractions on dielectric, piezoelectric, mechanical and microstructure properties of the composites were investigated. The ratio range of the composites constituent components was determined to enhance mechanical properties. Carbon fiber was used as reinforcing material to enhance the mechanical properties of PZT/PVDF composites. The results showed that PZT/PVDF composites doping with properly carbon fiber had a good compactness, and the relative dielectric constant (εr), the piezoelectric strain constant (d33) and the polarisability were all increased. Finally, the optimal proportion of PZT/PVDF was 50%/50% and carbon fiber content was 0.25%, the d33 of composite increased 14.2%, bending strength increased 7.2% and tensile strength increased 11.5%.
关键词： Tensile Strength,PZT/PVDF,Carbon Fiber,Electrical Properties,Bending Strength
更新于2025-09-09 09:28:46
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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Investigation of the Effects of High Temperature Aging on the Mechanical Behavior of Lead Free Solders
摘要： Lead free solders are renowned as interconnects in electronic packaging due to their relatively high melting point, attractive mechanical properties, thermal cycling reliability, and environment friendly chemical properties. The mechanical behavior of lead free solders is highly dependent on the operating temperature. Previous investigations on mechanical characterization of lead free solders have mainly emphasized stress-strain and creep testing at temperatures up to 125 °C. However, electronic devices, sometimes, experience harsh environment applications including well drilling, geothermal energy, automotive power electronics, and aerospace engines where solders are exposed to very high temperatures from 125-200 °C. Mechanical properties of lead free solders at elevated temperatures are limited. In this work, we have investigated the mechanical behavior SAC305 (96.5Sn-3.0Ag-0.5Cu) and SAC_Q (SAC+Bi) lead free solders at extreme high temperatures up to 200 °C. Stress-strain tests were performed on reflowed uniaxial specimens at four elevated temperatures (T = 125, 150, 175, and 200 °C). In addition, changes of the mechanical behavior of these alloys due to isothermal aging at T = 125 oC have been studied. Extreme care has been taken during specimen preparation so that the fabricated solder uniaxial test specimens accurately reflect the solder material microstructures present in actual lead free solder joints. High temperature tensile properties of the solders including initial modulus, yield stress, and ultimate tensile strength have been compared. As expected, our results show substantial degradations of the mechanical properties of lead-free solders at higher temperatures. With prior aging, these degradations become even more significant. Comparison of the results has shown that the addition of Bi to traditional SAC alloys improves their high temperature properties and significantly reduces their aging induced degradations.
关键词： Yield Stress,Ultimate Tensile Strength,Stress-Strain Curve,SAC alloy,Modulus,Lead-Free Solder,Aging
更新于2025-09-09 09:28:46
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Mechanical property modeling of photosensitive liquid resin in stereolithography additive manufacturing: Bridging degree of cure with tensile strength and hardness
摘要： Owing to the unique layer-wise production method, additive manufacturing technologies have been widely adopted in rapid prototyping and tooling areas, which often require superior mechanical properties such as tensile strength and hardness. In current literature, most mechanical property studies focusing on additive manufactured materials mainly adopt experimental or simulation-based approaches, and therefore cannot be directly used to accurately estimate and predict the achieved mechanical properties. In addition, information regarding the mechanical properties of photosensitive liquid resin used in the Stereolithography additive manufacturing process is limited. Hence, in this paper, mathematical models are established to quantify the tensile strength and hardness of Stereolithography fabricated materials by estimating the solidification levels of both green parts and Ultraviolet post-cured parts. The established degree of cure model is shown to have an average prediction accuracy of around 94%. In addition, the mechanical property models have an average accuracy of 88% and 90% for tensile strength prediction, and 98% and 95% for hardness prediction of green parts and post-cured parts, respectively. It is also observed that the Ultraviolet post-curing process has the capability of significantly enhancing the studied mechanical properties.
关键词： degree of cure,tensile strength,Additive manufacturing,hardness,photosensitive liquid resin,mechanical property
更新于2025-09-09 09:28:46