- 标题
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Aluminum with dispersed nanoparticles by laser additive manufacturing
摘要： While laser-printed metals do not tend to match the mechanical properties and thermal stability of conventionally-processed metals, incorporating and dispersing nanoparticles in them should enhance their performance. However, this remains difficult to do during laser additive manufacturing. Here, we show that aluminum reinforced by nanoparticles can be deposited layer-by-layer via laser melting of nanocomposite powders, which enhance the laser absorption by almost one order of magnitude compared to pure aluminum powders. The laser printed nanocomposite delivers a yield strength of up to 1000 MPa, plasticity over 10%, and Young’s modulus of approximately 200 GPa, offering one of the highest specific Young’s modulus and specific yield strengths among structural metals, as well as an improved specific strength and thermal stability up to 400 °C compared to other aluminum-based materials. The improved performance is attributed to a high density of well-dispersed nanoparticles, strong interfacial bonding between nanoparticles and Al matrix, and ultrafine grain sizes.
关键词： mechanical properties,aluminum,laser additive manufacturing,thermal stability,nanoparticles
更新于2025-09-11 14:15:04
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Effect of post heat treatment on the phase composition and strength of laser welded joints of an Al–Mg–Li alloy
摘要： In the present work, the effects of laser beam welding and post-weld heat treatment on the phase composition and mechanical properties of the 1424 alloy (Al–Mg–Li) joints were investigated. Holding the joints at a certain temperature was followed by quenching and artificial aging. The structural studies were carried out using electron microscopy, conventional X-ray diffractometry, and synchrotron radiation diffractometry. The heat treatment conditions were optimized to favor the formation of strengthening phases in the welds, the presence of which imparted mechanical strength to the joints. For the first time, 1424 Al alloy joints with a weld strength of σuts = 500 MPa have been obtained; this value of strength was achieved by applying post-weld annealing followed by quenching and artificial aging.
关键词： X-ray diffraction,Aluminum-lithium alloy,Laser welding,Electron microscopy,Synchrotron radiation,Mechanical properties
更新于2025-09-11 14:15:04
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The effect of different scanning strategies on microstructural evolution to 24CrNiMo alloy steel during direct laser deposition
摘要： 24CrNiMo alloy steel is a low-alloy high strength steel and was used to fabricate engine components and brake discs. In the current study, Direct Laser Deposition (DLD) was used to additively manufacture 24CrNiMo alloy steel samples with high strength and ductility. The microstructural evolution, texture and mechanical properties of deposited samples can be affected by changing inter-layer time intervals and scanning strategy between deposited layers. The granular bainite (GB) and lath martensite (LM) inside deposited samples were obtained by inter-layer successive deposition and 2-minute intervals deposition, respectively, because of the different cooling rates of different inter-layer time intervals. The occurrence of 2-minute intervals between cladding layers leads to higher cooling rates, resulting in finer grain size. In addition, the relatively strong textures could be transformed into the weak ones since the columnar dendrites were fragmented by the different heat transfer directions resulting from a scanning strategy of 90°-rotation between cladding layers. Less inclusions and un-melted powders inside deposited samples were obtained when a scanning strategy of 90°-rotation between deposited layers was applied. The experimental results indicate that a deposited sample with excellent tensile properties and microhardness was fabricated by an optimized laser scanning strategy. The optimized scanning strategy mainly include inter-layer 2-minute intervals and 90°-rotation between deposited layers. Deposited samples fabricated by the optimized scanning strategy have comparable tensile strength and ductility to those of other forged low-alloy high strength steel. Therefore, this optimized laser scanning strategy can be applied to manufacture low-alloy steel with high tensile properties.
关键词： microstructural evolution,scanning strategy,direct laser deposition,mechanical properties,24CrNiMo alloy steel
更新于2025-09-11 14:15:04
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Temperature- and Time-Dependent Mechanical Behavior of Post-Treated IN625 Alloy Processed by Laser Powder Bed Fusion
摘要： The microstructure and mechanical properties of IN625 alloy processed by laser powder bed fusion (LPBF) and then subjected to stress relief annealing, high temperature solution treatment, and hot isostatic pressing were studied. Tensile testing to failure was carried out in the 25–871°C temperature range. Creep testing was conducted at 760°C under 0.5–0.9 yield stress conditions. The results of the present study provided valuable insights into the static and creep properties of LPBF IN625 alloy, as compared to a wrought annealed alloy of similar composition. It was shown that at temperatures below 538°C, the mechanical resistance and elongation to failure of the LPBF alloy were similar to those of its wrought counterpart, whereas at higher temperatures, the elongation to failure of the LPBF alloy became significantly lower than that of the wrought alloy. The solution-treated LPBF alloy exhibited significantly improved creep properties at 760°C as compared to the wrought annealed alloy, especially under intermediate and low levels of stress.
关键词： additive manufacturing,nickel-based superalloys,high temperature mechanical properties,creep resistance
更新于2025-09-11 14:15:04
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Ring-like laser spot welding of Ti grade2 to AAl3105-O using AlSiMg filler metal
摘要： A pulsed Nd:YAG laser welding of 1 mm thick Ti (grade 2) to 0.5 mm thick AA3105-O was performed by a ring-like spot joining. A 0.15 mm thick Al-12Si-2.5Mg alloy was used as a filler metal. Intermetallic compounds of Ti3Al, Ti2Al, TiAl, Ti(Al,Si)3 and Mg2Si were observed respectively from Ti towards Al sides at the fusion zone. Si and Mg increased the strength of the Al re-solidified zone near the Ti-Al interface because of their easy dissolution in the Al. Exothermic effect of the Mg addition resulted in porosity in the welding zone. Joint strength of up to 98% of the Al base metal was obtained, which was much 14 % higher than that achieved by autogenous welding.
关键词： Titanium,Filler Metal,Laser Spot Welding,Microstructure and Mechanical Properties,Aluminum Alloy
更新于2025-09-11 14:15:04
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Studying the mix design and investigating the photocatalytic performance of pervious concrete containing TiO2-Soaked recycled aggregates
摘要： Demolished concrete, as one main form of construction and demolition wastes, has been widely studied of being utilized as recycled aggregates (RAs) in new concrete production. However, existing studies of applying RAs have been limited to the mechanical and durability issues of cementitious composites containing RAs. There has not been sufficient research of adopting RAs in cementitious products to also address the environmental sustainability. On the other hand, existing research utilizing cementitious products (e.g., concrete pavement) for air purification purpose have not adequately considered RA usage. Aiming to address the two sustainable objectives (i.e., waste diversion and air purification) simultaneously in concrete mix, this research adopted a two-step approach. Firstly, we studied and identified the optimal mix design of pervious concrete containing TiO2-soaked recycled coarse aggregates (RCAs) in order to achieve the higher compressive strength; secondly, we investigated the photocatalytic performance of pervious concrete containing RCAs coated with TiO2 photocatalysts. The photocatalytic performance of pervious concrete was also tested by applying a 10-min heavy rainwater wash. Experimental test results revealed that the internal voids of adhered mortar enabled RCAs to absorb more TiO2 particles. The NO degradation rate of TiO2-soaked RCAs increased from 71.4% to 80.6% when RCAs’ size decreased from 15-20 mm to 5e10 mm. The orthogonal experimental investigation indicated that water-to-binder ratio had the most significant effect on concrete compressive strength, followed by ratio of RCAs to binder, and replacement ratio of RCAs to natural aggregates. The optimized mix design for pervious concrete containing RCAs was identified to achieve highest strength (i.e., water-to-binder ratio at 0.35, coarse aggregate-to-binder ratio of 3 by mass, fly ash replacement rate to Portland cement at 5%, and 50% replacement ratio of RCAs to NCAs). The concentration of TiO2 solution at 0.3% was identified as the optimal ratio to achieve the highest NO degradation rate at 70% before rainwater wash. The NO degradation rates of pervious concrete still reached nearly 50% after 10-min heavy rainwater wash, indicating that pervious concrete using RCAs coated with TiO2 could largely maintain its photocatalytic capacity. This study addresses two main social and environmental issues in developing countries (e.g., China), namely overwhelming amount of construction & demolition wastes being generated, and air pollution. It leads to the cleaner production in concrete pavement construction by achieving the optimization between waste reuse, air purification, and engineering properties of porous concrete.
关键词： Pervious concrete,Photocatalytic effects,Mechanical properties,Recycled aggregate concrete,Titanium dioxide,Recycled aggregate
更新于2025-09-11 14:15:04
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Remelt processing and microstructure of selective laser melted Ti25Ta
摘要： In this study, elemental powder mixtures of Ti25Ta, an alloy with promise for orthopaedic applications, were processed using Selective Laser Melting (SLM), an emerging manufacturing method for bespoke implants. Material density and homogeneity was investigated as a function of laser scan speed and scanning strategy. Dense (> 99.99 %), pore free material was obtained at optimised processing parameters and a ‘remelt’ scan strategy improved melting of the Ta powders, avoiding keyhole formation. Tensile and ultrasonic modulus testing of the SLM Ti25Ta revealed that the processed material has a similar yield strength to SLM commercially pure Ti, namely 426 ± 15 MPa, with a significant reduction of elastic modulus to 65 ± 5 GPa. The remelt scan strategy increased the yield strength to 545 ± 9 MPa, without altering the elastic modulus, however reduced the elongation from 25 ± 1 to 11 ± 4 %. TEM analysis revealed the microstructure consisted of predominantly hexagonal α′ martensite with a limited amount of orthorhombic α′′ martensite formed in the Ta-rich regions near partially melted Ta particles, specifically facilitated by enhanced diffusion occurring during the remelt scan. The composition range for the α′′ phase was observed to be approximately 40-50 wt.% Ta. Electron back-scattered imaging (BSI) and back scattered diffraction (EBSD) revealed the formation of the prior β grains with close to equiaxed morphology and a slight texture in the α′ martensite. The application of the remelt scan disrupted the prior β grain structure and resulted in randomly oriented α′ laths.
关键词： Mechanical properties,Biomedical,Selective laser melting,Titanium,Tantalum
更新于2025-09-11 14:15:04
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Thermographic Monitoring of Laser Cutting Machine
摘要： Computer Numerical Controlled (CNC) laser cutting tools are developing as an alternative to conventional cutting systems thanks to increased accuracy, non-contact processing, higher productivity, less energy demand. An IR camera is utilized to monitor the laser cutting process of a steel plate. Even though the process is very complicated an analytical solution of the temperature ?eld generated on a slab by a point source moving along one direction of the plate surface is provided in order to interpret the temperature ?eld experimentally obtained by the IR camera.
关键词： mechanical properties,laser cutting machine,IR thermography
更新于2025-09-11 14:15:04
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Correlations between Process Parameters and Outcome Properties of Laser-Sintered Polyamide
摘要： As additive manufacturing (AM) becomes more accessible, correlating process parameters with geometric and mechanical properties is an important topic. Because the number of process variables in AM is large, extensive studies must be conducted in order to underline every particular influence. The study focuses on two variables—part orientation in the orthogonal horizontal plane and energy density—and targets two outcomes—geometric and tensile properties of the parts. The AM process was conducted on selective laser sintering (SLS) machine EOS Formiga P100 using EOS white powder polyamide (PA2200). After finishing the sinterization process, the parts were postprocessed, measured, weighted, and mechanically tested. The geometric evaluation and mass measurements of every sample allowed us to compute the density of all parts according to the sinterization energy and orientation, and to determine the relative error of every dimension. By conducting the tensile testing, the elastic and strength properties were determined according to process variables. A linear trend regarding sample density and energy density was identified. Also, large relative dimensional errors were recorded for the lowest energy density. Mechanical properties encountered the highest value for the highest energy density at a 45° orientation angle.
关键词： additive manufacturing,sample orientation,laser sintering,energy density,mechanical properties,polymer processing
更新于2025-09-11 14:15:04
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Al–Cu Alloy Fabricated by Novel Laser-TIG Hybrid Additive Manufacturing
摘要： Owing to its high strength to weight ratio, Al–Cu alloy is extensively used in the aeronautic and aerospace industries. However, there are some shortcomings in the additive manufacturing of Al–Cu alloy, such as cracks and poor strength. In this work, Al–Cu (2219-Al) specimens with excellent mechanical properties were fabricated by laser-TIG hybrid additive manufacturing. From microstructural studies, the average grain size in the laser zone (LZ) decreased to 14.4 μm, which was approximately 40.3% smaller than that in the arc zone (AZ). A {100} texture could be observed along the deposition direction. Under the influence of laser stirring, Cu in the LZ was distributed more uniformly than in the AZ. An incoherent θ phase, at the nanoscale, was discovered in both the AZ and the LZ. Its crystal orientation relationship was described as [110]α∥[002]θ, (110)α∥(002)θ between the α-Al matrix and the θ phase. The semi-coherent θ′ phase was observed in the LZ. Meanwhile, the θ′ phase characterized a good coherent relationship with the α-Al matrix, which resulted in low phase boundary energy. Furthermore, the deposited specimens exhibited a yield strength of 155.5 ± 7.9 MPa and an ultimate tensile strength of 301.5 ± 16.7 MPa, with an elongation of 12.8 ± 2.8%. These mechanical properties were higher than in specimens fabricated by TIG, CMT and SLM methods. The improved properties were predominately related to the smaller size of eutectics, the uniform distribution of Cu and the semi-coherent θ′ phases in the LZ. The combined effect of laser and arc can yield components with excellent mechanical properties, promoting the material for an expansive range of applications.
关键词： Additive manufacturing,Mechanical properties,Microstructure evaluation,Laser-TIG hybrid,Aluminum alloy
更新于2025-09-11 14:15:04