2021年, 第18卷, 第4期　
刊出日期：2021-07-28
  

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    Special Review
  • A review of additive manufacturing technology and its application to foundry in China
    Shi-yan Tang, Li Yang, Zi-tian Fan, Wen-ming Jiang, Xin-wang Liu
    《中国铸造》英文版. 2021, 18(4): 249-264. https://doi.org/10.1007/s41230-021-1003-0
    摘要 ( ) PDF全文 ( )   可视化   收藏
    The application of additive manufacturing technology is one of the main approaches to achieving the rapid casting. Additive manufacturing technology can directly prepare casting molds (cores) with no need of patterns, and quickly cast complex castings. The combination of additive manufacturing and traditional casting technology can break the constraint of traditional casting technology, improve casting flexibility, and ameliorate the working environment. Besides, additive manufacturing promotes the realization of "free casting", greatly simplifying the processing procedures and shortening the manufacturing cycle. This paper summarizes the basic principle of additive manufacturing technology and its development situation domestically and overseas, mainly focusing on the development status of several main additive manufacturing technologies applicable to the foundry field, including three-dimensional printing, selective laser sintering, stereolithography, layered extrusion forming, etc. Finally, the future development trend of additive manufacturing technology in the foundry field is prospected.
  • In situ monitoring methods for selective laser melting additive manufacturing process based on images — A review
    Bo Wu, Xiao-yuan Ji, Jian-xin Zhou, Huan-qing Yang, Dong-jian Peng, Ze-ming Wang, Yuan-jie Wu, Ya-jun Yin
    《中国铸造》英文版. 2021, 18(4): 265-285. https://doi.org/10.1007/s41230-021-1111-x
    摘要 ( ) PDF全文 ( )   可视化   收藏
    Selective laser melting (SLM) has been widely used in the fields of aviation, aerospace and die manufacturing due to its ability to produce metal components with arbitrarily complex shapes. However, the instability of SLM process often leads to quality fluctuation of the formed component, which hinders the further development and application of SLM. In situ quality control during SLM process is an effective solution to the quality fluctuation of formed components. However, the basic premise of feedback control during SLM process is the rapid and accurate diagnosis of the quality. Therefore, an in situ monitoring method of SLM process, which provides quality diagnosis information for feedback control, became one of the research hotspots in this field in recent years. In this paper, the research progress of in situ monitoring during SLM process based on images is reviewed. Firstly, the significance of in situ monitoring during SLM process is analyzed. Then, the image information source of SLM process, the image acquisition systems for different detection objects (the molten pool region, the scanned layer and the powder spread layer) and the methods of the image information analysis, detection and recognition are reviewed and analyzed. Through review and analysis, it is found that the existing image analysis and detection methods during SLM process are mainly based on traditional image processing methods combined with traditional machine learning models. Finally, the main development direction of in situ monitoring during SLM process is proposed by combining with the frontier technology of image-based computer vision.
  • Additive manufacturing and foundry innovation
    Yu-sheng Shi, Jin-liang Zhang, Shi-feng Wen, Bo Song, Chun-ze Yan, Qing-song Wei, Jia-min Wu, Ya-jun Yin, Jian-xin Zhou, Rui Chen, Wei Zhou, He-ping Jia, Huan-qing Yang, Hai Nan
    《中国铸造》英文版. 2021, 18(4): 286-295. https://doi.org/10.1007/s41230-021-1008-8
    摘要 ( ) PDF全文 ( )   可视化   收藏
    Additive manufacturing is expected to transform and upgrade the traditional foundry industry to realize the integrated manufacturing and rapid and low-cost development of high-performance components with complex shapes. The additive manufacturing technology commonly applied in casting mold preparation (fusible molds, sand molds/cores and ceramic cores) mainly includes selective laser sintering (SLS) and binder injection three-dimensional printing (3DP). In this work, the research status of SLS/3DP-casting processes on material preparation, equipment development, process optimization, simulation and application cases in aerospace, automotive and other fields were elaborated. Finally, the developing trends of the additive manufacturing technology in the future of foundry field are introduced, including multi-material sand molds (metal core included), ceramic core-shell integration and die-casting dies with conformal cooling runners.
  • Rapid casting technology based on selective laser sintering
    Li Yang, Shi-yan Tang, Zi-tian Fan, Wen-ming Jiang, Xin-wang Liu
    《中国铸造》英文版. 2021, 18(4): 296-306. https://doi.org/10.1007/s41230-021-1099-2
    摘要 ( ) PDF全文 ( )   可视化   收藏
    Selective laser sintering (SLS), as a kind of additive manufacturing technology, which uses a laser beam to scan and heat powder material layer by layer to form parts (models), is widely used in the field of casting, mainly for preparing casting coated sand cores, investment casting patterns, etc. The SLS technique facilitates rapid casting and shortens the casting production periods by eliminating mold preparation. In this study, we reached conclusions for the basic principles and characteristics of SLS methods, and focused on the research status, key technology and development trend of SLS in the fields of forming coated sand-casting molds and investment casting patterns.
  • Mechanical properties of TiAl fabricated by electron beam melting—A review
    Bo-chao Lin, Wei Chen
    《中国铸造》英文版. 2021, 18(4): 307-316. https://doi.org/10.1007/s41230-021-1093-8
    摘要 ( ) PDF全文 ( )   可视化   收藏
    As a typical intermetallic material, TiAl is inevitably difficult to process by conventional methods. Additive manufacturing (AM) has recently become a new option for making net-shape TiAl components. Among all AM methods, electron beam melting (EBM) shows the potential to make TiAl components with good mechanical properties and is used for low pressure turbine blades. The mechanical properties, including tensile and compression properties, fracture toughness, fatigue and creep properties of EBM TiAl are reviewed and compared to the conventionally fabricated alloys. Results show that the tensile strength of EBM alloys is higher than cast alloys, and other properties are comparable to the cast/forged alloys. The sensitivity of mechanical properties and microstructure to EBM processing parameters is presented. Issues including layered microstructure, anisotropy in mechanical properties, and fatigue failure from defects are also reviewed. Finally, some opportunities and challenges of EBM TiAl are identified.
  • A review on metal additive manufacturing: modeling and application of numerical simulation for heat and mass transfer and microstructure evolution
    Chuan-ming Liu, Hua-bing Gao, Li-yu Li, Jian-dong Wang, Chun-huan Guo, Feng-chun Jiang
    《中国铸造》英文版. 2021, 18(4): 317-334. https://doi.org/10.1007/s41230-021-1119-2
    摘要 ( ) PDF全文 ( )   可视化   收藏
    Metal additive manufacturing technology has been widely used in prototyping, parts manufacturing and repairing. Metal additive manufacturing is a multi-scale and multi-physical coupling process with complex physical phenomena of heat and mass transfer and microstructure evolution. It is hard to directly observe the dynamic behavior and microstructure evolution of molten pool during additive manufacturing. Therefore, numerical simulation of additive manufacturing process is significant since it can efficiently and pertinently predict and analyze the physical phenomena in the process of metal additive manufacturing, and provide a reference for technological parameters selection. In this review, the research progress of numerical simulation of metal additive manufacturing is discussed. Various aspects of numerical simulation models are reviewed, including:(1) Introduction of basic control method and physical description of numerical simulation models; (2) Comparison of various heat and mass transfer models based on different physical assumptions (heat conduction model; heat flux coupling model; discrete powder particle heat flux coupling model); (3) Applications of various microstructure evolution models[phase field (PF), cellular automata (CA), and Monte Carlo (MC)]. Finally, the development trend of numerical simulation of metal additive manufacturing, including the thermal-flow-solid coupling model and deep learning for numerical model, is analyzed.
    • Research & Development
  • Binder jetting 3D printing process optimization for rapid casting of green parts with high tensile strength
    Zhao-fa Zhang, Li Wang, Lin-tao Zhang, Peng-fei Ma, Bing-heng Lu, Chen-wei Du
    《中国铸造》英文版. 2021, 18(4): 335-343. https://doi.org/10.1007/s41230-021-1057-z
    摘要 ( ) PDF全文 ( )   可视化   收藏
    Binder jetting 3D printing is a rapid, cost effective, and efficient moulding/core making process, which can be applied to a large variety of materials. However, it exhibits a relatively low green-part strength. This may cause the collapse of the printed parts during de-caking and the pick-up procedure, especially in the case of small-scale structures, such as thin walls, tips, and channels. In this work, polyvinyl alcohol (PVA) was used as the additive in coated sand powder. By exploiting the binding effect between the two composites (thermoplastic phenolic resin and PVA) triggered by the binder, bonding necks firmly form among the sand particles, improving the green-part strength of the coated sand printed parts. Experiments based on the Taguchi method were used to investigate the relationship between the process parameters and the green-part tensile strength. The following set of optimal process parameters was identified:50wt.% alcoholicity of the binder, 75% binder saturation, 0.36 mm layer thickness and 4.5wt.% PVA content. Further, the effect of such parameters on the green-part tensile strength was determined via statistical analysis. The green part of an engine cylinder head sand pattern with complex cavity structures was printed, and the green-part tensile strength reached 2.31 MPa. Moreover, the ZL301 aluminum alloy impeller shape casting was prepared using sand molds printed with the optimal process parameters. The results confirm that the proposed binder jetting 3D printing process can guarantee the integrity of the printed green parts and of small-size structures during decaking and the pick-up procedure. Furthermore, the casting made from the printed sand molds exhibits a relatively high quality.
  • Sand-bed defect recognition for 3D sand printing based on deep residual network
    Lan-xiu Wang, Xuan-pu Dong, Shu-ren Guo
    《中国铸造》英文版. 2021, 18(4): 344-350. https://doi.org/10.1007/s41230-021-1091-x
    摘要 ( ) PDF全文 ( )   可视化   收藏
    The 3D sand printing (3DSP), by binder jetting technology for rapid casting, has a pivotal role in promoting the development of the traditional casting industry as a result of producing high-quality and economical sand molds. This work presents an approach for monitoring and analyzing powder sand-bed images to serve as a realtime control system in a 3DSP machine. A deep residual network (ResNet) is used to classify the defects occurring during the powder spreading stage of the process. Firstly, a pre-trained network was applied as the initial parameter; then it was fine-tuned on the labelled defective sample dataset to accomplish the task, which defines the sand-bed defects induced in the 3DSP processing. Furthermore, the recognition and positioning of sand-bed defects were readily achieved by dividing the sand-bed images into blocks. Experiments show that the fine-tuned network has a 98.7% classification accuracy on the validation dataset of sand-bed defects and 95.4% recognition accuracy for the sand-bed images.
  • Performance of Ti6Al4V fabricated by electron beam and laser hybrid preheating and selective melting strategy
    Mo-han Hao, Lei Zhang, Bin Zhou, Hong-xin Li, Ming-zhi Li, Feng Lin
    《中国铸造》英文版. 2021, 18(4): 351-359. https://doi.org/10.1007/s41230-021-1039-1
    摘要 ( ) PDF全文 ( )   可视化   收藏
    Electron beam selective melting (EBM) and selective laser melting (SLM) are regarded as significant manufacturing processes for near-net-shaped Ti6Al4V components. Generally, in the conventional EBM process, preheating is necessitated to avoid "smoke" caused by the charging of electrons. In the conventional SLM process, laser as an energy source without the risk of "smoke" can be employed to melt metal powder at low temperatures. However, because of the low absorption rate of laser, the powder bed temperature cannot reach a high level. It is difficult to obtain as-built TiAl4V with favorable comprehensive properties via conventional EBM or SLM. Hence, two types of electron beam and laser hybrid preheating (EB-LHP) combined with selective melting strategies are proposed. Using laser to preheat powder allows EBM to be performed at a low powder bed temperature (EBM-LT), whereas using an electron beam to preheat powder allows SLM to be performed at a high powder bed temperature (SLM-HT). Ti6Al4V samples are fabricated using two different manufacturing strategies (i.e., EBM-LT and SLM-HT) and two conventional processes, i.e., EBM at a high powder bed temperature (EBM-HT) and SLM at a low powder bed temperature (SLM-LT). The temperature-dependent surface quality, microstructure, density, and mechanical properties of the as-built Ti6Al4V samples are characterized and compared. Results show that EBM-LT Ti6Al4V exhibits a higher ultimate tensile strength (981±43 MPa) and a lower elongation (12.2%±2.3%) than EBM-HT Ti6Al4V owing to the presence of α' martensite. The SLM-HT Ti6Al4V possesses the highest ultimate tensile strength (1,059±62 MPa) and an elongation (14.8%±4.0%) comparable to that of the EBM-HT Ti6Al4V (16.6%±1.2%).
  • Laser ultrasonic testing for near-surface defects inspection of 316L stainless steel fabricated by laser powder bed fusion
    Ting Dai, Xiao-jian Jia, Jun Zhang, Jin-feng Wu, Yi-wei Sun, Shu-xian Yuan, Guan-bing Ma, Xiao-jing Xiong, Hui Ding
    《中国铸造》英文版. 2021, 18(4): 360-368. https://doi.org/10.1007/s41230-021-1063-1
    摘要 ( ) PDF全文 ( )   可视化   收藏
    The laser powder bed fusion (L-PBF) method of additive manufacturing (AM) is increasingly used in various industrial manufacturing fields due to its high material utilization and design freedom of parts. However, the parts produced by L-PBF usually contain such defects as crack and porosity because of the technological characteristics of L-PBF, which affect the quality of the product. Laser ultrasonic testing (LUT) is a potential technology for on-line testing of the L-PBF process. It is a non-contact and non-destructive approach based on signals from abundant waveforms with a wide frequency-band. In this study, a method of LUT for on-line inspection of L-PBF process was proposed, and a system of LUT was established approaching the actual environment of on-line detection to evaluate the method applicability for defects detection of L-PBF parts. The detection results of near-surface defects in L-PBF 316L stainless steel parts show that the crack-type defects with a sub-millimeter level within 0.5 mm depth can be identified, and accordingly, the positions and dimensions information can be acquired. The results were verified by X-ray computed tomography, which indicates that the present method exhibits great potential for on-line inspection of AM processes.
  • Effects of geometrical characteristics on defect distributions in alloy components produced by selective laser melting
    Yao Cai, Tao Lu, Gui-dian Ma, Wang Li, Ye Pan, Hui Ding
    《中国铸造》英文版. 2021, 18(4): 369-378. https://doi.org/10.1007/s41230-021-1048-0
    摘要 ( ) PDF全文 ( )   可视化   收藏
    Selective laser melting (SLM) has been applied to manufacture various alloy components with excellent properties, but its further application is restricted by the intrinsic defects. In this work, the internal defect distributions in samples of three alloys (316L stainless steel, AlSi10Mg and Inconel 718) were investigated respectively, considering the effects of geometrical characteristics of the samples. The defects in the 316L stainless steel sample tend to be formed densely in the central part with large wall thickness, indicating a strong sensitivity to heat accumulation. Contrarily, the Inconel 718 sample shows a higher relative density with homogeneous defect distribution, indicating better formability for the SLM process. For the AlSi10Mg sample, the defect density keeps increasing as the deposition goes on. Typically, the defect density located at sample edges shows an abnormally high level comparing with the inner part, especially in the top sections of AlSi10Mg and Inconel 718 samples. The results are helpful for the geometrical design, the adjustment of building orientation and the further optimization of process parameters in the SLM process.
  • Influence of laser parameters on segregation of Nb during selective laser melting of Inconel 718
    Liang Wang, Ran Cui, Bin-qiang Li, Xue Jia, Long-hui Yao, Yan-qing Su, Jing-jie Guo, Tong Liu
    《中国铸造》英文版. 2021, 18(4): 379-388. https://doi.org/10.1007/s41230-021-1088-5
    摘要 ( ) PDF全文 ( )   可视化   收藏
    A transient three-dimensional powder-scale model was established for understanding the flow field and mass transfer within the molten pool during the selective laser melting (SLM) of Inconel 718 alloy by considering some important physical phenomena, such as, a transition from powder to solid, nonlinearities produced by temperature-dependent materials' properties, and fluid flow in the calculation. The influence of laser power or scanning speed on the flow field and cooling rate was discussed in detail. The simulation results reveal that the motion of molten pool and higher cooling rate promote the mass transfer and benefit the solute distribution by increasing laser power. However, with increasing the scanning speed, the melt flow speed and cooling rate are elevated, resulting in an agglomeration of the solute elements, which is ascribed to the shorter dwelling time of liquid. Therefore, the segregation of Nb can be effectively suppressed by increasing laser power or decreasing scanning speed, which can decrease the dwelling time of liquid.
  • Influence of hot isostatic pressing on microstructure, properties and deformability of selective laser melting TC4 alloy
    Tai-qi Yan, Bing-qing Chen, Xia Ji, Shao-qing Guo
    《中国铸造》英文版. 2021, 18(4): 389-396. https://doi.org/10.1007/s41230-021-1086-7
    摘要 ( ) PDF全文 ( )   可视化   收藏
    The influence of different hot isostatic pressing regimes on microstructure, phase constitution, microhardness, tensile properties and deformability of TC4 alloy fabricated by selective laser melting (SLM) technology was studied. The results show that the microstructure of SLM TC4 alloy is composed of acicular martensite α' phase, and the sample exhibits high microhardness and strength, but low plasticity. After hot isostatic pressing, acicular martensite α' phase transforms into α+β phase, and with the increase of hot isostatic pressing temperature and duration, α phase with coarse lath is gradually refined, and the proportion of α phase is gradually reduced. Because of the change of phase constitution in SLM TC4 alloy after hot isostatic pressing, the grain refinement strengthening is weakened, the density of dislocation is reduced, so that both microhardness and tensile strength are decreased by around 20%, the elongation is increased by more than about 70%, even over 100%, compared with as-deposited TC4 alloy. When the hot isostatic pressing regime is 940℃/3 h/150 MPa, the tensile strength and the elongation achieve optimal match, which are about 890 MPa and around 14.0% in both directions. The fracture mechanism of alloy after 940℃/3 h/150 MPa HIP is dultile fracture. Hot isostatic pressing causes concave deformation of SLM TC4 alloy thin-walled frames, and the deformation degree increases with the increase of temperature.
  • Phase constitution, microstructure and mechanical properties of a Ni-based superalloy specially designed for additive manufacturing
    Bin Wu, Jing-jing Liang, Yan-hong Yang, Jin-guo Li, Yi-zhou Zhou
    《中国铸造》英文版. 2021, 18(4): 397-408. https://doi.org/10.1007/s41230-021-9025-1
    摘要 ( ) PDF全文 ( )   可视化   收藏
    In this study, a kind of Ni-based superalloy specially designed for additive manufacturing (AM) was investigated. Thermo-Calc simulation and differential scanning calorimetry (DSC) analysis were used to determine phases and their transformation temperature. Experimental specimens were prepared by laser metal deposition (LMD) and traditional casting method. Microstructure, phase constitution and mechanical properties of the alloy were characterized by scanning electron microscopy (SEM), transmission scanning electron microscopy (TEM), X-ray diffraction (XRD) and tensile tests. The results show that this alloy contains two basic phases, γ/γ', in addition to these phases, at least two secondary phases may be present, such as MC carbides and Laves phases. Furthermore, the as-deposited alloy has finer dendrite, its mean primary dendrite arm space (PDAS) is about 30-45 μm, and the average size of γ' particles is 100-150 nm. However, the dendrite size of the as-cast alloy is much larger and its PDAS is 300-500 μm with secondary and even third dendrite arms. Correspondingly, the alloy displays different tensile behavior with different processing methods, and the as-deposited specimen shows better ultimate tensile stress (1,085.7±51.7 MPa), yield stress (697±19.5 MPa) and elongation (25.8%±2.2%) than that of the as-cast specimen. The differences in mechanical properties of the alloy are due to the different morphology and size of dendrites, γ', and Laves phase, and the segregation of elements, etc. Such important information would be helpful for alloy application as well as new alloy development.
  • Transient printing characteristics with wavy build profiles for laser additive manufacturing of small size structures
    Fu-qin Liu, Hui-liang Wei, Lei Wei, Ting-ting Liu, Wen-he Liao
    《中国铸造》英文版. 2021, 18(4): 409-415. https://doi.org/10.1007/s41230-021-1001-2
    摘要 ( ) PDF全文 ( )   可视化   收藏
    Laser directed energy deposition (DED) is a multi-physics process that accompanies mass flow, energy transfer, and complex phase transitions. The printing characteristics of small size parts are significantly affected by the progressive variations of the temperature fields and the fluid flow within the molten pool. In this work, the deposition characteristics during multi-layer and multi-track laser DED were explored through a well-tested phenomenological model and corresponding experimental results. The variations of the build profiles and the decoupled track and layer profiles were systematically examined. Moreover, the printing characteristics of the builds with different scanning lengths were compared. Results showed that the multi-layer and multi-track transient deposition processes generated a significantly wavy surface profile. Compared with the long scanning length part, the beginning region of the short build produced an obvious bulge followed by sharply decreased height along the scanning direction. The transverse section of the short build varied significantly at different positions. Two adjacent columns of tracks were extracted from the overall build, demonstrating that the tracks tilted outwards and the angle increases along the scanning direction. The 3D numerical model was validated with corresponding experiments for builds with various layers. The scientific findings from this work can provide useful insights for the understanding of the additive mechanisms during laser DED for the precise shape control of small size parts.
  • Microstructure and properties of AlSi7Mg alloy fabricated by selective laser melting
    Shuai Huang, Shao-qing Guo, Biao Zhou, Guo-hui Zhang, Xue-jun Zhang
    《中国铸造》英文版. 2021, 18(4): 416-423. https://doi.org/10.1007/s41230-021-1004-z
    摘要 ( ) PDF全文 ( )   可视化   收藏
    The AlSi7Mg alloy was fabricated by selective laser melting (SLM), and its microstructure and properties at different building directions after heat treatment were analyzed. Results show that the microstructure of SLM AlSi7Mg samples containes three zones:fine grain zone, coarse grain zone, and heat affected zone. The fine-grain regions locate inside the molten pool, and the grains are equiaxed. The coarse-grain regions locate in the overlap of molten pools. After T6 treatment, the microstructure at the molten pool boundary is still the network eutectic Si, but the network structure becomes discrete, and is composed of intermittent, chain-like eutectic Si particles. The yield strength at three directions (xy, 45°, z direction) of the AlSi7Mg alloy samples fabricated by SLM is improved after T6 heat treatment. The fracture mechanism of the samples is a mixed ductile and brittle fracture before heat treatment and ductile fracture after heat treatment.
  • Design for Ti-Al-V-Mo-Nb alloys for laser additive manufacturing based on a cluster model and on their microstructure and properties
    Tian-yu Liu, Zhi-hao Zhu, Shuang Zhang, Xiao-hua Min, Chuang Dong
    《中国铸造》英文版. 2021, 18(4): 424-432. https://doi.org/10.1007/s41230-021-1065-z
    摘要 ( ) PDF全文 ( )   可视化   收藏
    In this study, α+β Ti-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing (LAM) were designed according to a Ti-6Al-4V cluster formula. This formula can be expressed as 12[Al-Ti12](AlTi2)+5[Al-Ti14]((Mo, V, Nb)2Ti), in which Mo and Nb were added into the alloys partially instead of V to give alloys with nominal compositions of Ti-6.01Al-3.13V-1.43Nb, Ti-5.97Al-2.33V-2.93Mo, and Ti-5.97Al-2.33V-2.20Mo-0.71Nb (wt.%). The microstructures and mechanical properties of the as-deposited and heat-treated samples prepared via LAM were examined. The sizes of the β columnar grains and α laths in the Nb-containing samples are found to be larger than those of the Ti-6Al-4V alloy, whereas Mo- or Mo/Nb-added alloys contain finer grains. It indicates that Nb gives rise to coarsened β columnar grains and α laths, while Mo significantly refines them. Furthermore, the single addition of Nb improves the elongation, whereas the single addition of Mo enhances the strength of the alloys. The simultaneous addition of Mo/Nb significantly improves the comprehensive mechanical properties of the alloys, leading to the best properties with an ultimate tensile strength of 1,070 MPa, a yield strength of 1,004 MPa, an elongation of 9%, and micro-hardness of 355 HV. The fracture modes of all the alloys are ductile-brittle mixed fracture.
《中国铸造》英文版
China Foundry
ISSN 1672-6421
CN 21-1498/TG

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