2021年, 第18卷, 第6期　
刊出日期：2021-12-28

  

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Research & Development
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  Influence of different high pressure die casting processes on 3D porosity distribution of Mg-3.0Nd-0.3Zn-0.6Zr alloy

  Yi-hu Ma, Wen-bo Yu, Yu-qi Zhou, Shou-mei Xiong

  《中国铸造》英文版. 2021, 18(6): 521-528. https://doi.org/10.1007/s41230-021-1068-9

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  3D reconstruction was adopted to characterize the microstructural morphologies of Mg-3.0Nd-0.3Zn-0.6Zr alloy castings produced by high pressure die casting (HPDC) processes with different parameters,including low slow-shot speed,solidification pressurization and fast slow-shot speed.At low slow-shot speeds of 0.1 m·s^-1,0.2 m·s^-1 and 0.3 m·s^-1,the porosity is concentrated in the center of the castings with one spiral staggered shape along the liquid flow direction.The porosity volume simultaneously decreases with the reduction of quantity and size of externally solidified crystals (ESCs),while the shrinkage pores become more and more dispersed with the increasing low slow-shot speed.Pressurization not only reduces the porosity volume due to the improvement of feeding ability,but also transformes the center gathered porosity into one layer-by-layer distribution form.Accompanied with the increasing fast slow-shot speed,the central porosity dramatically decreases and transforms into a large-scale spiral staggered shape along the liquid flow direction.However,the porosity is much more dispersed when the speed is increased from 2 m·s^-1 to 3 m·s^-1.
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  Effects of particle size, bimodality and heat treatment on mechanical properties of pumice reinforced aluminum syntactic foams produced by cold chamber die casting

  Çağın Bolat, İsmail Cem Akgün, Ali Gökşenli

  《中国铸造》英文版. 2021, 18(6): 529-540. https://doi.org/10.1007/s41230-021-1133-4

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  In recent years,metal matrix syntactic foams (MMSFs) have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1–2 mm,2–4 mm,and bimodal (50vol.%) natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^-3 depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.
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  Phase-field modeling of dendritic growth of magnesium alloys with a parallel-adaptive mesh refinement algorithm

  Bing-hui Tian, Meng-wu Wu, Ang Zhang, Zhi-peng Guo, Shou-mei Xiong

  《中国铸造》英文版. 2021, 18(6): 541-549. https://doi.org/10.1007/s41230-021-1116-5

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  A two-dimensional phase field (PF) model was developed to simulate the dendritic solidification in magnesium alloy with hcp crystal structure.By applying a parallel-adaptive mesh refinement (Para-AMR) algorithm,the computational efficiency of the numerical model was greatly improved.Based on the PF model,a series of simulation cases were conducted and the results showed that the anisotropy coefficient and coupling coefficient had a great influence on the dendritic morphology of magnesium alloy.The dendritic growth kinetics was determined by the undercooling and equilibrium solute partition coefficient.A significant finding is acquired that with a large undercooling,the maximum solute concentration is located on both sides of the dendrite tip in the liquid,whereas the maximum solute concentration gradient is located right ahead of the dendrite tip in the liquid.The dendrite tip growth velocity decreases with the increase of the equilibrium solute partition coefficient,while the variation trend of the dendrite tip radius is the opposite.Quantitative analysis was carried out relating to the dendritic morphology and growth kinetics,and the simulated results are consistent with the theoretical models proposed in the previously published works.
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  Phenomena at three-phase electroslag remelting

  Zhong-li Liu, Lev Medovar, Ganna Stovpchenko, Volodymyr Petrenko, Artem Sybir, Yev. Volchenkov

  《中国铸造》英文版. 2021, 18(6): 557-564. https://doi.org/10.1007/s41230-021-0125-8

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  The electroslag remelting (ESR) process is widely used to produce high-quality ingots and billets for high-alloyed steels and alloys.Both the single-phase and three-phase alternating current diagram with bifilar and monofilar connection are in use for heavy ingot manufacturing.The numerical simulation of the three-phase bifilar circuit for the 120 t three-phase bifilar six-electrode ESR furnace at different variants of electric connection was presented and discussed.At the bifilar diagram of power supply,the geometrical location of electrodes in a mould holds critical importance for performances:the close location of bifilar pair electrodes provides the highest heat productivity,but the equidistant location of electrodes gives a much more uniform heat distribution.The monofilar mulit-electrode diagram of three-phase connection without phase shift shows the most uniform distribution of potential and heat generation as well as a favorable magnetic field that makes this kind the most promising for providing a high quality of heavy ingots.
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  Effects of SiC_p on microstructures of semi-solid extruded AZ91D magnesium alloys in recrystallization process

  Ao-xue Jiang, Zhi-yong You, Zhuang-zheng Duan, Gang-ping Qiao, Jin-shan Zhang, Ling-bing Guo

  《中国铸造》英文版. 2021, 18(6): 565-573. https://doi.org/10.1007/s41230-021-1005-y

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  AZ91D and 8.5vol.% SiC_p/AZ91D magnesium matrix composites were fabricated by a semi-solid extruded processing method,and treated with solution and aging heat treatment.The effects of SiC_p on the microstructures of the semi-solid extruded AZ91D magnesium alloy during recrystallization were studied by observing and analyzing the microstructure evolution during extrusions and heat treatments.The results show that the addition of SiC_p inhibits the dynamic recrystallization of AZ91D during the semi-solid extrusion with only 26% of the volume fraction of recrystallization.Furthermore,the addition of SiC_p refines the sizes of grains and second phases,and upgrades the volume fraction of second phase.After solution and aging treatment,the recrystallization continues,and the addition of SiC_p promotes the recrystallization and the recrystallized microstructure is much more stable.Meanwhile,the sizes of grains and second phases continue to be refined,and the volume fraction of second phases continues to increase.
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  Microstructure and mechanical properties of laser additive manufactured novel titanium alloy after heat treatment

  Tian-yu Liu, Hong-yu Liu, Qian Yao, Shi-bing Liu, Kun Shi, Zhi-yong Zhang, Chong-yang Li

  《中国铸造》英文版. 2021, 18(6): 574-580. https://doi.org/10.1007/s41230-021-1089-4

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  A novel α+β titanium alloy with multi-alloying addition was designed based on the cluster formula 12[Al-Ti₁₂](AlTi₂)+5[Al-Ti₁₄](AlV_1.2Mo_0.6Nb_0.2) which was derived from Ti-6Al-4V.The nominal composition of this novel alloy was determined as Ti-6.83Al-2.28V-2.14Mo-0.69Nb-6.79Zr.In this study,the novel alloy and Ti-6Al-4V alloy samples were prepared by laser additive manufacturing.The microstructure,micro-hardness,room/high temperature tensile properties of the as-deposited samples were investigated.Compared to Ti-6Al-4V,the novel alloy has much higher room and high temperature (600℃) tensile strengths,which are 1,427.5 MPa and 642.2 MPa,respectively;however,it has a much lower elongation (3.2%) at room temperature because of the finer microstructure.To improve the elongation of the novel alloy,heat treatment was used.After solution at 960℃ or 970℃ for 1 h followed by air cooling and aging at 550℃ for 4 h followed by air cooling,a unique bi-modal microstructure which contains crab-like primary α and residual β phase is obtained,improving the compression elongation by 80.9% compared to the as-deposited samples.The novel alloy can be used as a high-temperature and high-strength candidate for laser additive manufacturing.
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  Effect of gel time of 3D sand printing binder system on quality of sand mold/core

  Yan Wang, Rui-long Yu, Shao-kui Yin, Rui Tan, Yan-chun Lou

  《中国铸造》英文版. 2021, 18(6): 581-586. https://doi.org/10.1007/s41230-021-1085-8

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  Two important factors affecting the performance of sand mold/core generated by 3D printing (3DP) are strength and dimensional accuracy,which are not only closely related to the reactivity of furan resin and the phase transition of silica sand,but also the curing agent system of furan resin.This paper studies the influence of gel time on the strength and dimensional accuracy of a 3DP sand mold/core,taking the furan resin system as an example and using a sand specimen generated by a 3DP inkjet molding machine.The experiment demonstrates that the gel time of 3 to 6 min for the sand mixture suits 3DP core-making most under the experimental condition.However,it should be noted that under the same resin condition,the strength of a no-bake sand mold/core is higher than that of a 3DP sand mold/core.The dimensional accuracy of the sand mold/core does not change significantly when the gel time is less than 15 min.Improving the activity of binder and developing ultra-strong acid with low corrosion shall be an effective way to improve the quality of the mold/core by 3D printing.
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  Development of 3D printing entity slicing software

  Yang Guan, Xun Sun, Lei Jin, Xin-li Guo, Zhi-min Zhang, Guo-yan Shui, Lan-bo Ma

  《中国铸造》英文版. 2021, 18(6): 587-592. https://doi.org/10.1007/s41230-021-1090-y

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  Based on STL (stereo lithography) format file and with Microsoft Visual C⁺⁺ 6.0 programming language,a 3D printing slicing software appropriate for the surface strengthening of the parts has been developed,which includes three functions:3D model import,model slicing and data export.Through the grouping of STL model triangle facets before slicing,the judgment times of the relationship between the triangle facets and the cutting planes are reduced,and the slicing efficiency is improved.Aiming at the fact that the surface should be strengthened when the part is formed by using of 3D printing process,the function of identifying and marking the surface of the geometric entity is accomplished in the slicing software,which can strengthen the surface of the part according to the user’s requirements.The developed slicing software can provide an entity slicing file for 3D printing equipment.The related functions can be adjusted and improved according to user’s needs,which makes the software convenient and flexible to use.
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  Properties of alumina-based ceramic cores

  Xiao-fu Liu, Xin-li Guo, Guo-yan Shui, Chang-chun Li, Gui-qiao Su, Xun Sun, Yang Guan, Lei Jin

  《中国铸造》英文版. 2021, 18(6): 593-598. https://doi.org/10.1007/s41230-021-1125-4

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  Fused corundum is a rather promising raw material for preparing an alumina-based ceramic core due to its excellent high temperature resistance and chemical inertness.In this study,alumina-based ceramic cores were prepared using fused corundum as the matrix material,and the effect of varying silica powder contents on the properties of the alumina-based ceramic cores,including the sintering shrinkage,the flexural strength,and the high temperature deformation was investigated.The mineralization mechanisms of the silica on the alumina-based ceramic core were also analyzed.The optimum addition amount of silica in this experiment is 8% in weight.At that moment,the aluminum-based core has both a low sintering shrinkage coefficient of 0.66% and better properties:the room temperature flexural strength is 22.19 MPa,the high temperature flexural strength is 21.54 MPa,the high temperature deformation is 0.93 mm,and the residual flexural strength is 47.41 MPa.