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Jeon, Jin Myoung,Park, Jeong Min,Yu, Ji-Hun,Kim, Jung Gi,Seong, Yujin,Park, Sun Hong,Kim, Hyoung Seop Elsevier Sequoia 2019 Materials science & engineering Structural materia Vol.763 No.-
<P><B>Abstract</B></P> <P>In this study, the anisotropic and asymmetric mechanical behaviors of 316 L stainless steel processed using selective laser melting, were investigated experimentally and theoretically by performing tension and compression tests along different directions of the sample. Significant anisotropic and asymmetric behaviors were observed due to the effects of microstructure and internal defects. Severe anisotropy in stress level and elongation were found in the tensile behavior, while compression behavior exhibited somewhat different yield strength and strain hardening with loading direction. Finite element simulations based on the real microstructure and microstructural analysis confirmed that pore shape and molten pool boundary are the major reasons for the mechanical anisotropy and asymmetry. This result supports a guideline for designing parts and the scanning directions used in selective laser melting.</P>
Lasers in Additive Manufacturing: A Review
이협,김영진,Chin Huat Joel Lim,Mun Ji Low,Nicholas Tham,Vadakke Matham Murukeshan 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.4 No.3
In recent years, additive manufacturing, also known as three-dimensional (3D) printing, has emerged as an environmentally friendly green manufacturing technology which brings great benefits, such as energy saving, less material consumption, and efficient production. These advantages are attributed to the successive material deposition at designated target areas by delivering the energy on it. In this regard, lasers are the most effective energy source in additive manufacturing since the laser beam can transfer a large amount of energy into micro-scale focal region instantaneously to solidify or cure materials in air, therefore enabling high-precision and high-throughput manufacturing for a wide range of materials. In this paper, we introduce laser-based additive manufacturing methods and review the types of lasers widely used in 3D printing machines. Important laser parameters relevant to additive manufacturing will be analyzed and general guidelines for selecting suitable lasers for additive manufacturing will be provided. Discussion on future prospects of laser technologies for additive manufacturing will be finally covered.
Anton Yu. Nalivaiko,Dmitriy Yu. Ozherelkov,Ivan A. Pelevin,Stanislav V. Chernyshikhin,Andrey E. Medvedev,Andrey V. Korshunov,Alexey N. Arnautov,Alexander A. Gromov 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.3
The synthesis features for 3D samples of AlSi10MgCualloy were investigated. Two types of samples were used: single tracksand cubic samples of 10 mm3volumes obtained by selective laser melting. 3D printing regimes and samples characteristicswere compared for both types of samples. A comprehensive characterization of the initial AlSi10MgCualloy powder wasperformed. The morphology, microstructure, and micro-hardness of the obtained single tracks and cubic samples werestudied. The mechanism of the porosity formation was discussed in detail. A formation of pores and non–uniform structureswas evidently caused by non–equilibrium crystallization during the selective laser melting process, namely 3D samples fastcooling. The lower porosity and the more uniform structure were obtained with higher values of laser power (from 220 to240 W) Values of laser power had a crucial influence on the morphology and microstructure of the obtained 3D material. Optimal modes for selective laser melting for experimental AlSi10MgCupowder were revealed based on the microstructureand micro-hardness data. The values of the micro-hardness were varied from 115.5 to 151.1 HV. The micro-hardness forsamples was increased on average by 20 HV after additional heat treatment. It was caused, most probably, by the separationof the Al2Cuphase.
Zihao Jiang,Yayun Li,Hang Luo,Baogang Zhou,Yilong Liang,Yu Liang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12
The present work investigated the effect of the boundary orientation of melt pool on the mechanical properties and fracturepath in selective-laser-melted AlSi10Mg alloy. The acquired data are beneficial for understanding the influence of themicrostructure on mechanical properties. During the alloy’s selective laser melting (SLM), the melt pool boundary wasalmost parallel with the scanning direction, and the grains grew along the building direction. When the load-bearing facewas perpendicular to the melt pool boundary, the crack propagation path deflected towards coarse melt pool of the melt poolboundary, reducing the probability of directly crossing the fine melt pool. Otherwise, the cracks would mainly propagatealong the melt pool boundary. In the tensile deformation process, coarse melt pool (CMP) was subjected to higher localstrain than fine melt pool (FMP) and heat-affected zone (HAZ), and the crack propagated or deflected along the CMP inthe melt pool boundary. Therefore, the anisotropy of mechanical properties in SLM AlSi10Mg was mainly ascribed to theCMP density on the load-bearing face. As a weak area, the high proportion of CMP significantly reduced the strength andplasticity of the alloy.
Wenlin Ye,Jin Bao,Jie Lei,Yicheng Huang,Zhihao Li,Peisheng Li,Ying Zhang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.1
A mesoscopic simulation based on random packing powder bed model was established to study the heat behavior of CP-Tiduring selective laser melting. The characteristics of the molten pool under the interaction of laser and powder, and theinfuence of laser power on the thermal behavior, hydrodynamics and surface morphology evolution of the molten pool werestudied. The results show that with the increase of laser power, the maximum temperature, temperature change rate, lifetimeof molten pool and size are greatly improved. In addition, the characteristics and heat behavior of the molten pool under thedouble track are mainly studied in this study. It is found that the maximum temperature, lifetime, and the length and width ofthe molten pool of the second track are higher than those in the frst, and with the increase of laser power, the length widthratio of the second track in molten pool becomes larger
Bandar AlMangour,Jinquan Cheng,Dariusz Grzesiak,Yu‑Jin Hwang,Kee‑Ahn Lee 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.2
The low density and high biocompatibility of Mg-based materials make them suitable for lightweight structural and biomedicalapplications. In this study, we explored the use of selective laser melting (SLM)–an additive manufacturing processwherein metal powders are consolidated in a layer-by-layer manner, allowing the fabrication of complex components. SLMtypically involves complex physicochemical phenomena and results in laser-processing defects, which makes it difficult topredict the densification mechanisms of the melt pool. Therefore, a full-scale model was developed to investigate the thermalbehavior of the melt pool (e.g., temperature gradient distribution, melt pool dimensions, and cooling rate) and the resultantdensification activity under various laser energy density (η) values. In parallel, experimental investigations of the densificationbehavior and microstructural evolution were undertaken with the same SLM processing parameters. The challengesassociated with the SLM processability of Mg were comprehensively addressed. Both the peak temperature gradients withinthe molten pool and molten pool dimensions increased with increasing η, and an opposite trend was observed for the coolingrate. A low η (i.e., high scanning speed) results in a low operating temperature and short liquid lifetime, which in turn leadto poor wettability and many pore-chain and balling defects. However, high η values generated melt pool instability, whichresulted in extensive evaporation, cracks, and porosity. The SLM-processed samples had fine twin-like microstructures asa result of rapid solidification. The experimental and simulation results agreed well, validating the thermal behavior of themolten pool and underlying physical mechanism.
Z. Y. Duan(돤쯔양),J. Suhr(서종환) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
Martensitic stainless steels have gained renewed interest recently for their use in automotive, aerospace, and defense applications due to their ultra-high yield strengths and reasonable ductility. Herein, by using optimized process parameters, we report the successfully manufactured 410 martensitic stainless steel using Selective Laser Melting (SLM). Bulk 410 was printed to high part qualities with an excellent combination of tensile properties of 1,100 ± 20 Mpa yield strength, 1,280 ± 5 Mpa ultimate tensile strength, and 13.5% ± 0.6% fracture elongation. This unique performance is attributed to the alternating distribution of ferrite, ultra-fine tempered martensite, nano-sized austenite, and retained martensite produced by the SLM process. Moreover, due to the inherent heat treatment phenomenon in the SLM process, the distribution of ultrafine and heterogeneous grains is formed, which is believed to promote good ductility. This work proved that the high-performance martensitic stainless steel parts could be prepared through SLM by using appropriate processing parameters.
Fabrication of Fe-based bulk metallic glass by selective laser melting: A parameter study
Jung, H.Y.,Choi, S.J.,Prashanth, K.G.,Stoica, M.,Scudino, S.,Yi, S.,Kuhn, U.,Kim, D.H.,Kim, K.B.,Eckert, J. Elsevier Ltd 2015 Materials & Design Vol.86 No.-
Soft magnetic Fe-based bulk metallic glass cylindrical specimens with a diameter of 2mm and height of 6mm have been successfully fabricated by selective laser melting (SLM) and the effect of scan speed v and laser power P on the microstructure, thermal stability and soft magnetic properties has been investigated. The results indicate that low v and high P lead to the formation of SLM samples with high relative densities, which can reach values of about 99.7%. This can be ascribed to the optimal energy transfer during processing at low v and high P. Structural and calorimetric studies prove that the SLM samples are fully amorphous. In addition, magnetic measurements reveal that the amorphous structure of the SLM material is identical to the parent atomized powders. Although additional work is required to remove the residual porosity and to avoid the formation of cracks during processing, the present results confirm that additive manufacturing by SLM represents an alternative processing route for the preparation of bulk metallic glass components with designed geometry having excellent magnetic softness.