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Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the laser powder bed fusion (LPBF) manufacturing, the thermal history differences caused by the building direction may lead to variations in grain morphology, defect quantity, and phase composition of metallic components, thereby impacting the mechanical and functional performances of the components. This study was designed to investigate the effects of three building directions, 0°, 45°, and 90°, on the microstructure and mechanical properties of LPBF-fabricated NiTi shape memory alloys. The microstructure and transformation behaviors were analyzed using scanning electron microscopy (SEM), optical microscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The mechanical and functional performances of NiTi alloys in both martensitic and austenitic states were evaluated through temperature-controlled tensile testing. The results indicate that the melt pool types for the 0°, 45°, and 90° samples are conduction mode, mixed mode, and keyhole mode, respectively. At room temperature and 100 ℃, the tensile strains of the 0°, 45°, and 90° samples are 10.5%/8.5%, 17%/11%, and 9.5%/5.5%, respectively. After tensile pre-deformed to 6% at room temperature, the shape memory strains of the three groups of samples are 3.3%, 3.4%, and 3.8%, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Laser powder bed fusion （LPBF） technology offers significant advantages， including high flexibility， no mold requirements， and rapid manufacturing capabilities， so it is well-suited for repairing complex and precision components such as aero-engine blades. It is difficult to efficiently and accurately reveal the evolution rules of defects and microstructures in the multi-scale and multi-physical field coupling LPBF process through experimental methods only. The finite volume method and a cellular automaton model were used to simulate the morphological evolution of the powder bed melt pool and the corresponding microstructure formation process. Combined with experimental observations， the evolution rules of metallurgical defects in the alloy and grain growth under different printing parameters are revealed. The results indicate that during the LPBF repair process， energy density significantly affects the morphology of the melt pool. When the energy density is less than 87.9 J/mm³， the powder particles are not completely melted， accompanied by the formation of defects such as pores and unmelted areas. When the energy density is greater than 137.4 J/mm³， the surface smoothness of the solidified melt pool is significantly reduced. The increase in energy density enhances the horizontal thermal flow disturbance in the melt pool， and the crystals are affected by shear forces， leading to a greater orientation difference with the substrate. Additionally， the laser power significantly affects the microstructure of the alloy. As the laser power increases， the temperature gradient gradually decreases. The low temperature gradient promotes the formation of the supercooled liquid region， which in turn facilitates the formation of new crystal nuclei. When the laser power increases from 150 W to 250 W， the epitaxial growth grains change from columnar crystals to a large number of polycrystalline grains. Based on the numerical simulation methods， the optimal process parameters for repairing DZ125 alloy by LPBF are determined as follows：P=200 W， V=1000 mm/s， and H=65 μm. This method helps to reduce experimental costs and accelerate the acquisition of reasonable process parameters for LPBF repair of alloys.

The composition of Fe–30Mn–11Al–12Ni–1C lightweight alloy steels was designed and the effect of laser power on the microstructure and properties of the lightweight steels formed by laser powder bed fusion (LPBF) was studied in this paper. The results show that the relative density of lightweight steel samples formed by LPBF increases gradually with the increase of laser power at a constant scanning speed, and the relative density of samples formed at 120 W is the highest, reaching 99.2%. Under the different laser power, the unfused regions appear in the plane parallel to the construction direction (XOY), and the cracks appear in the plane perpendicular to the construction direction (XOZ). The defect types on the XOY observation plane are different from the XOZ observation plane, which are reflected in the following aspects: XOY plane has a large number of unfused pores, spherical powders, and large holes, and with the increase of laser power, the unfused defects and hole areas gradually decrease, and the spherical powders disappear; the defects on the XOZ plane are mainly holes and cracks, with the increase of laser power, the holes decrease gradually, but the crack width increases. The hardness of samples shows anisotropy, and the anisotropy gradually decreases with the increase of laser power. The hardness on the XOZ plane does not change obviously with laser power, but it is higher than the XOY plane. The microhardness on the XOY plane changes greatly, because the laser power increases and the effect of defects is reduced. When the laser power is 120 W, the hardness on the XOZ plane reaches the maximum as HV0.2 441.3. With laser power of 90 W and scanning speed of 800 mm·s−1, the yield strength and tensile strength of the formed light steel samples reach the maximum value, which are 800.8 MPa and 825.4 MPa respectively. There is a large amount of the precipitated phase at the grain boundary of the samples, resulting in the low elongation of all the samples, so the plasticity of the LPBF formed light steel is poor.

Laser powder bed fusion (LPBF), an additive manufacturing technology, is extensively applied in various fields. In the building process, one or more laser beams scan and melt the powder previously deposited on the build platform, following a prescribed scanning path to achieve the designed three-dimensional geometry. After the current powder layer is selectively melted and solidified, another layer of powder is spread, and the laser scanning continues. Such repetitive operations exhibit inherent rapid heating and cooling characteristics, resulting in uneven microstructures and the accumulation of internal stresses for the produced parts. For the most widely used Ti–6Al–4V, this LPBF characteristic forms fine needle-like α′ martensite and small amounts of beta phase. There is a phase potential difference between the α′ and the β phases, which constitutes a corrosive galvanic battery, and the corrosion reaction preferentially occurs at the phase interface of the α′ and the β phases. However, as a metastable structure, the thermodynamic stability of the α′ phase is lower than that of the β phase, which makes the α′ phase preferentially corroded. Moreover, the V element enrichment in the β phase imparts stability, exerting a significant inhibitory effect on the corrosion and dissolution of the Ti–6Al–4V alloy. This is evident in the denser and more stable passive film formed on the β phase compared with that on the α′ or α phase, accompanied by a corresponding increase in corrosion resistance. To better meet different service conditions, it is imperative to regulate its microstructure and alleviate residual stresses through heat treatment as a heat-treatable α + β type titanium alloy. However, the optimal heat treatment conditions for LPBF Ti–6Al–4V are being determined. We aim to provide a comprehensive overview of the current literature, focusing on the perspective that the properties of a material are inherently influenced by its microstructure. Specifically, the correlation between microstructure and corrosion resistance in LPBF-produced Ti–6Al–4V before and after heat treatment is explored. The influence of post-heat treatment on the microstructure and corrosion behavior of LPBF-produced Ti–6Al–4V is also discussed. Results reveal that appropriate heat treatment can facilitate the decomposition of fine needle-like α′ martensite and the formation of β phases, enhancing the corrosion resistance of LPBF-produced Ti–6Al–4V. However, excessive heat treatment will increase the grain size of the LPBF Ti–6Al–4V and deteriorate the corrosion resistance. Finally, conclusions are drawn, which is expected to bring some support to researchers.

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

6061 aluminum matrix composites added by 3% diamond particles (mass fraction) were prepared by laser powder bed fusion (LPBF). The microstructure, relative density, and tensile properties of the 3%diamond/6061 aluminum matrix composites were characterized and analyzed by optical microscope, scanning electron microscope, X-ray diffractometer, electronic densitometer, and electronic universal testing machine. Results show that the diamond reacts with the Al matrix, generating the needle-like Al4C3 phase, which deposits in the α-Al matrix. Those formed Al4C3 increases dislocations at the grain boundaries, enhances the materials’ strength, and delays the failure to fracture. The addition of diamond facilitates the elimination of thermal cracks, but the porous defects remain in 6061 aluminum alloys. The lower scanning speed extends the contact duration between the laser spot and the processed material, leading to the graphitization of the added diamond and the partial evaporation of the Al matrix. Thus, the internal defects exist, exhibiting the low densification of the composite (relative density 97%). The addition of diamond significantly increases the tensile strength of the LPBF formed diamond/6061 aluminum matrix composites, and the ultimate tensile strength reaches the maximum value of 244.2 MPa, the yield strength is 211.6 MPa, and the elongation is 2.1%, respectively, when the laser power is 350 W and the scanning speed is 800 mm·s−1.

The AlSi10Mg alloy samples were successfully prepared by laser powder bed fusion（LPBF）. The effects of three kinds of heat treatment process，namely 130 ℃/4 h aging treatment，236 ℃/10 h annealing treatment，and 540 ℃/1 h solid solution treatment on the microstructure of the AlSi10Mg samples were investigated. After heat treatment，the evolution of coefficient of thermal expansion（CTE） and thermal conductivity of the AlSi10Mg alloy in the temperature range from room temperature to 400 ℃ was examined. The results show that spherical Si particles are precipitated within the aluminum matrix，while the complete network-like eutectic silicon structure is retained after aging treatment. After annealing，the network-like silicon structure is disappeared completely，and spherical Si particles are uniformly distributed within the matrix. After solution treatment，large blocky Si particles with the sizes from 1 μm to 3 μm appear. The thermal properties of the AlSi10Mg alloy have been improved significantly after heat treatment compared to the as-printed state. In particular，the CTE of alloy subjected to annealing is 1.64×10−5 ℃−1 to 2.1×10−5 ℃−1 within the temperature range from room temperature to 400 ℃，the average thermal conductivity is 179.6 W·m−1·K−1，the performance is superior to ageing and solution treatments.

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A three-dimensional finite element thermal model was established, combined with the finite element software ANSYS, and the simulation of applying a Gaussian heat source and the printing process of WC-12Co cemented carbide was achieved with the use of APDL commands and the birth-death unit method, and the temperature field distribution of WC-12Co cemented carbide in the laser powder bed fusion (LPBF) shaping process was finally obtained, and the effects of different process parameters (laser power, scanning speed) on its temperature field distribution and melt pool characteristics were investigated. The results show that the forming process of WC-12Co cemented carbide in LPBF process can be effectively simulated by using finite elements. In addition, the isotherms located at the front of the heat source are denser than those at the tail, with a larger temperature gradient; and the temperature in the center of the melt pool at the terminal edge of the scanning path is the highest. As the laser power increases and the scanning speed decreases, the width, depth and length of the molten pool increase accordingly. Relevant experiments were used to analyze the effect of different process parameters on grain size, and it is found that the grain size decreases with the increase of scanning speeds and increaseds with the increase of laser power; but too high laser power can cause certain thermal cracking phenomenon.

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pure copper/copper alloy has excellent thermal and electrical conductivity, which is an important industrial material. Laser powder bed fusion, which represents the laser additive manufacturing technology, has excellent design freedom and forming accuracy, and is the mainstream development direction of additive manufacturing. Compared with traditional processing and manufacturing technology, the laser powder bed fusion of pure copper/copper alloy can give better play to the excellent performance of copper, and has broad application prospects in the fields of high thermal conductivity/electrical conductivity such as electrical and electronic, automotive, aerospace and other fields. The current research status of laser powder bed fusion of laser high-reflective materials represented by pure copper/copper alloys, the important problems they face, and the analysis of corresponding solutions were reviewed in this paper. On this basis, combined with the team's experience in the laser powder bed fusion process of pure copper/copper alloy, it was pointed out that the use of blue, green and other short-wavelength lasers for the powder bed laser fusion of pure copper/copper alloy and other highly reflective materials is a future study hot spots and development directions.

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)