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找到 39541 条结果
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2017年 3 TN.174期
摘要:This paper aims to study the use of fly ash as an additive material to enhance the nature of Furan molds which prevent casting defects such as sand holes and sintering by use of Taguchi method. The approach used in the study is the respective addition of 0 wt%, 3 wt%, 6 wt%, 9 wt% and 12 wt% fly ash to silica sand with different categories of 201V, 205V, 302V, 401V and 501V. At the same time, 3 wt%, 4 wt%, 5 wt%, 6 wt% and 7 wt% Furan resin (relative to the weight of sand), and 45 wt% the curing agent (relative to resin weight) were respectively added to different sizes of silicon sand. After mixing, the blended casting sand was poured into the standard test piece mold to form Furan molds. Until the sand being reacted 4hr, 8hr, 16hr, 24hr, 30hr, respectively, and these molds were then baked at 40℃, 60℃, 80℃, 100℃ and 120℃ for 20min, 40min, 60min, 80min and 100min respectively to explore the influence of using different ratios of fly ash, different ratios of furan resin, different particle sizes of silica sand on the compressive strength, permeability, and friability of Furan sand molds. As compared to the industrial molding condition (without fly ash) using 250V silica sand with 1.2 wt% resin and 45 wt % hardener under a reaction time of 24hr, the experimental results show that the condition of 3 wt% resin, 250V silica sand, 6 wt % fly ash and a reaction time of 24 hr under the baking temperature of 120℃ and baking time of 100 min can effectively increase 4.43 times on the compressive strength and 1.76 times on the permeability of a sand mold, while the friability can be decreased from 10.92% to 1.89%....
摘要:Electrical discharge alloying in combination with pulsed Nd:YAG laser remelting is the method intended for the surface modification of cast iron in this study. Spheroidal graphite cast iron for mold making was used as a base material while a carbide-forming element (Cr) that promotes the formation of hard and brittle carbide layers having good wear resistance was selected as electrode material. The test specimen that had undergone electrical discharge alloying with the optimal parameters were surface modified by pulsed Nd:YAG laser remelting under the conditions obtained through optimization testing. The results reveal that the specimens obtained from applying electrical discharge alloying (EDA) with the Cr electrodes have significantly higher hardness than those that received electrical discharge alloying and laser remelting (EDA+LR). However, the laser remelted layers have significantly less defects compared with the EDAed layers. The specimens obtained from applying electrical discharge alloying (EDA) with the Cr electrodes and the laser remelted specimens also exhibit better corrosion resistance compared to the base SG cast iron. Topographical observations of the surfaces of the modified layers reveal that the EDAed layers had significantly rougher surface than the laser remelted layers. The X-ray diffraction analysis shows that the main compositional phases in the EDA-ed layer with Cr are Cr_7C_3 and Cr_3C_2, while Cr_3C_2 and Fe_3C for the laser remelted layer....
摘要:Due to its excellent castability the ADC 12 die casting Al alloy is widely used for various consumer products. However, its applications as structural components are limited due to its poor mechanical properties, especially in ductility. Normally, the T6 treatment is seldom applied to the die casting components for improvement of their mechanical properties, since blistering problem may easily occur during solution treatment. As such, a study aims to improve its mechanical properties is conducted. A total of seven ADC12-type alloys were studied, including two commercial ADC12 alloys with different Si contents and five modified ADC12 alloys, namely ADC12(10 Si), ADC12(11 Si) and ADC12-1 ~ ADC12-5. The results showed that, among the various modified ADC12-type alloys examined, the ADC12-2 alloy with additions of 0.02% Sr, 0.3% Cr and 0.3% Zr exhibits proper microstructures in the as cast condition with promising mechanical properties. The Sr modifier and Cr neutralizer added to the alloy have modified the shapes of coarse plate-like eutectic Si into fibrous and the thin sheet-like β-Al_5FeSi into small particles of α-Al_(13)(Fe,Cr)_4Si_4, respectively. Tensile properties data show that the yield strength, tensile strength, elongation and quality index of the as-cast ADC12-2 alloy to be 259MPa, 345MPa, 3.9% and 434MPa, respectively. In comparison with the commercial ADC12(10 Si) alloy, the tensile elongation of ADC12-2 alloy is similar to that of ADC12(10 Si), but the yield strength and tensile strength are significantly higher than those of ADC12(10 Si) alloy....
摘要:This study is aimed at the effect of vacuum extraction power and solid solution temperature on the tensile properties of EPC lamp cover castings. Results reveal that the properties of castings are improved to a great extent under the condition with a larger vacuum extraction power of 30 Hp then a less vacuum extraction power of 7.5 Hp. The tensile properties are first increased and then decreased with the increase of solid solution temperature. The variation of properties is greatly affected by microstructure of EPC lamp cover castings under different condition....
摘要:Turbochargers have become more and more popular in automobile with the increasing awareness of environmental protection. Nickel-based superalloy IN713LC is used as a material for turbochargers currently. Therefore, increasing the high temperature strength of the IN713LC is the purpose of this study. In this study, the IN713LC nickel-based superalloy was successfully cast by vacuum induction melting (VIM). The test results indicate that the addition of boron has a significant increase in the high temperature strength of the IN713LC at 982℃. When the boron content is 0.012 wt%, the tensile strength has increased by 10% and the yield strength by 12%, compared to the base material. When the boron content is 0.015 wt%, the tensile strength has increased by 14% and the yield strength by 18%, compared to the base metal. It was found that boron is enriched in carbides at the grain boundaries or borides are formed around the eutectic phase after analysis of the microstructure by Scanning Electron Microscopy (SEM) and Electron Probe Microanalyzer(EPMA). When carbides or borides are discontinuously distributed at the grain boundaries, they can strengthen the grain boundaries and increase the high temperature mechanical properties of the material....
摘要:Environmental protection and energy saving is an important issue in recent years, the use of lightweight materials with improved mechanical properties is a direct and effective energy-saving method in the transport industry. An ADC3 Al alloy was used in this study as base material on improving the mechanical properties by means of alloy composition adjustment. The main theme of alloy composition adjustment includes adding a small amount of Sr to modify the morphology of eutectic Si and reducing the iron and magnesium contents to decrease the amount of brittle phases produced. The results in microstructural and mechanical properties change were examined by using optical and scanning electron microscopy, tensile test, fractography, etc. The results showed that, among the modified 0.4% Fe-content ADC3 series alloys studied, the ADC3S2 alloy exhibits the best mechanical properties with tensile strength of 178 MPa, elongation of 5.1% and quality index of 286 MPa. While that in the modified Fe-free ADC3 series alloys, the ADC3S7 showed the best result with tensile strength of 180 MPa, elongation of 8.1% and quality index of 319 MPa. A comparison in the mechanical properties of a typical ADC3 alloy (with tensile stress of 164 MPa and elongation of 1.7%) to the selected modified ADC3 alloys (ADC3S2 and ADC3S7) showed that the tensile strength and elongation of two modified alloys with reduced iron contents are improved by amounts of about 14 ~ 16 MPa and 3.4% ~ 6.4%, respectively....
摘要:This study deals with the blistering problem in die casting Al alloys when they are subjected to T6 heat treatment. In order to realize the onset temperature and time conditions for the blistering problem to occur, the common die casting alloys, namely ADC3 (Al-9.2 Si-0.4 Mg-0.3 Fe and with additions of 2% and 4% Cu), were used and subjected to a series of solid solutioning tests. Once the blistering onset conditions were identified, proper T6 heat treatment can be applied to the alloys without the occurrence of blistering. Through a careful selection of heat treatment conditions (not to exceed the blistering onset conditions) and proper adjustments of alloy compositions (to lower the required solid solution temperature) die casting alloys can be strengthened by the blistering-free T6 heat treatment....
摘要:Light weight die cast A380 Al alloy products with precision dimensions have been used extensively in transportation and 3C (computer, communication and consumer electronics) industries. However, their applications as structural components are limited in areas where a major or impact loading is applied. The reason why die casting A380 Al alloy products normally show poor elongation is because the castings normally contain a variety of brittle phases, including eutectic Si, β-Al_5FeSi and Al_2Cu(Mg) phases. As such, a series of five A380 base alloys, namely A380 and A380-1 to A380-4, was made for the study of alloying effects on the brittle phases in the alloys. This was conducted by adding a small amount of Sr to the A380 alloy to modify the morphology of eutectic Si, reducing the amount of Fe and adding Mn or Cr to modify the amount and the morphology of β-Al_5FeSi, and decreasing the amount of Cu and Mg to modify the amount and the compound structure of Al_2Cu(Mg) phase. The results showed that, the modified A380-1 alloy with composite-adjustment in alloying elements show a great improvement in ductility of 8.1%, as compared to the A380 alloy of 4.6%. And the modified Mg-free A380-4 alloys exhibits the highest ductility of 9.1%....
摘要:The aim of this study is to understand the effect of and anodizing time of citric acid or tartaric acid electrolytes on the anodic oxide film thickness and color of stepped castings made by A390 aluminum alloy with high silicon content. The results show that the larger oxide film thickness of A390 aluminum alloy casting anodized by citric acid or tartaric acid was obtained at the condition with the condition of anodized time of 15minutes at a fixed anodizing voltage of 225 volts. The oxide film thickness was increased with the increase of anodizing time or casting thickness. In addition, with the increase of anodizing time, the CIE L~*, a~* and b~* values of color on oxide film were reduced. Through OM and SEM + EDS observations, the oxide film of A390 aluminum alloy casting anodized by the citric acid revealed to be a dense morphology with few cracks. However, the oxide film for tartaric acid revealed to be a loose morphology with many cracks....
[期刊论文] Jau-Kwei Huang Fu-Yuan Hsu
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2015年 3 TN.166期
摘要:In resin bonded sand mold manufacturing process, the mixing of silica sand with resin binder is influenced by the physical properties of the binder. Its permeability which is the distance of the binder mass penetrating into the sand particles also affects the strength of sand mold. For the resin sand mold prepared by 3D printing route, as the binder droplet impacts on the sand bed, the binding strength of the mold will be influenced by the physical properties of both the binder (e.g., viscosity, density, surface tension, pH), and the sand particles, (e.g., particle size, bulk density, particle morphology). In this study, Computational Fluid Dynamics (CFD) package was used for measuring the distance of diffusion range of resin binder into porous sand bed during the binder droplet contacting the bed. These modeling results are validated by the real experiments....
[期刊论文] C. H. Hsu C. T. Hung H. T. Liu
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2014年 4 TN.163期
摘要:In this study, the ADI specimens were first heated at 900℃ for 1, 2, 4, and 6 minutes, respectively, and then quenched in water. The purpose is to explore the effect of holding time on microstructure, surface hardness, and wear resistance of ADI. The results show that there is a martensitic formation on the surface of ADI due to the quenching effect, resulting in an evident increase of hardness on the ADI's surface (450→950 HV_(0.1)). Moreover, the depth of case hardening increased with increasing holding time. However, it must be noticed that when holding time is 2 minutes, some micro-cracks take place on the internal structure of ADI with a mixture of ausferrite and martensite. When the holding time is over 4 minutes, the cracking could penetrate the surface. In contrast, the holding time controlled (~1 min) properly could not only avoid the generation of cracks, but also increase surface hardness of ADI to improve the wear resistance....
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2014年 2 TN.161期
摘要:At elevated temperature, molten pure Ti and Ti alloy is highly reactive with common mold materials. The aim of this investigation was to improve the pure titanium/investment mold material interfacial reaction by adding MgO into a novel investment mold material. The experimental results show the compression strength of sintered investment mold materials is in the range of 40~56 MPa, which can meet the demand of investment mold casting process. The compression strength of sintered materials decrease with the increase of sintering temperatures. Another, addition of 2.25-6.25 wt.% MgO into the investment material, the compression strength was improved, the phase of sintered investment changed from ZrO_2-Al_2O_3-SiO_2 to ZrO_2-MgO system, and the reaction layer was decreased....
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2017年 4 TN.175期
摘要:This study explores the results of machining and milling tests carried out to determine the effect of cutting tool types, machining and milling parameters of FCD 600 spheroidal graphite cast iron after austempering heat treatment on tool life and workpiece surface roughness. The cutting tools used in the machining and milling tests were PCBN coated tungsten carbide inserts, and TiAlN and TiSiN coating milling tools. The experiment results shows that the tools flank wear increases with the cutting time and machining speed increasing during the machining and milling tests. In addition, decreasing the cutting speed as one of the important operation factors in machining of ADI, does improve the tools life and workpiece surface roughness. In the milling test, results revel the tools flank wear and workpiece surface roughness of TiSiN coating milling tools were better than TiAlN coating milling tools. The best surface roughness Ra=0.75 μm was shown in the milling conditions of TiSiN coating milling tools and cutting speed =50 m/min....
[期刊论文] Z. P. Liu Y. N. Pan
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2015年 3 TN.166期
摘要:The objectives of this study are threefold: (1) To investigate the effect of homogenization heat treatment on both the degree of Ni segregation and the content of dissolved carbon in the matrix of the low thermal expansion ductile cast irons, and then to analyze the influence of compositional factor on a value. (2) To study the effects of alloy composition and homogenization heat treatment on the dimensional and shape changes of the test specimens by means of constrained thermal cyclic fatigue tests (30~200℃). (3) The temperature distribution and the thermal stress field in the test specimens after the constrained thermal cyclic fatigue tests were analyzed first by both calculation and simulation (ANSYS), and then the dimensional and shape changes of the alloys studied (Alloy D-5, Regular SG and SUS304) were calculated and compared with the measured data. In addition, the correlations among a value, thermal stress and dimensional change were analyzed. The experimental results indicate that the degree of Ni segregation can be reduced by increasing the homogenization temperature and/or time, rendering a decrease in a value. On the other hand, the dissolved C content in the matrix showed little affected by homogenization heat treatment, regardless of the fact that increasing both heat treatment temperature and time will increase the dissolved C content. Among the various heat treatment procedures employed, heat treatment T5(1150℃/4hr/FC/750℃/4hr) not only can effectively eliminate the Ni segregation, but also can reduce the C concentration in the matrix. It is clear from the equation below that in order to achieve a low a value, both the degree of Ni segregation and the dissolved C content should decrease. α(10~(-6)/℃) = 0.56Ni_d + 3.45%C + 2.74; R~2 = 0.86 Finally, numerical simulation by finite element method (FEM) was employed to obtain the temperature distribution and thermal stress field for different alloys (Alloy D-5, Regular SG and SUS304) after thermal cyclic fatigue tests. Regression analysis was performed to obtain the correlation between thermal stress and APV. The lower the thermal stress, the lower the APV value. Also, low thermal expansion ductile irons with T5 heat treatment (1150℃/4hr/FC/750℃/4hr/WQ) exhibit the best dimensional stability due to its lowest a value (2.86×10~(-6)/℃). Besides, regression analysis was performed to obtain the correlation between the thermal stress and the PV values, with the results were shown as follows: ΔPV(μm) = 0.87σ_(th)(Mpa)-35.6; R~2 =0.96. The results indicate a highly positive linear correlation between the PV value and the thermal stress....
摘要:An investigation on fine-grained casting process and mechanical behavior of CM 247 LC superalloy was carried out in this study. The alloy was remelted and cast to obtain the desired fine-grained test bars (70 μm) by controlling casting parameters. After casting, the specimens were through the processes of hot isostatic press, followed by determining the microstructural characteristics and investigating the tensile and creep performance at the various heat treatment processes. Tensile test results reveal that the yield strength of fine-grained test bars via multi-step 1254℃/2hr solution treatment increases relative to 1221℃/2hr solutioned specimens. Under the creep condition of intermediate temperature and high stress (760℃/200MPa), the fine-grained alloy heat-treated at 1221℃ /2hr+1080℃ /4hr+871℃ /20hr shows greater creep life and elongation than those of at high temperature of 1254℃. The reasons are related to formation of γ 'film at GBs and surrounding the GB carbide which is beneficial to the stress accomodation at GB and inhibits the crack initiation and propagation, On the contrary, the alloy heat-treated at 12.54℃/2hr+87rc/20hr demonstrates better creep life under high temperature and low stress (982℃/200MPa). This is due to high volume fraction of γ', proper γ' size and refinement of carbide, inhibiting the dislocation gliding and climbing. The results indicate that the CM 247 LC superalloy has excellent castability to form a fine grain structure. In addition, this alloy exhibits superior creep behaviors at various operation environments after at suitable heat treatment and microstructure control....
[期刊论文] A. N. Tsai C. H. Hsu
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2016年 3 TN.170期
摘要:In this study, the ductile iron (DI) was heat-treated via austempering and quenching/tempering methods to get the two types of ausferrite (ADI) and tempered martensite (TM) in microstructure. And then dry wear tests and polarization tests were conducted for exploring the effect of microstructure on wear and corrosion behavior of ductile iron. The experimental results showed that ductile iron after austempering and quenching/tempering treatments could be actually obtain the microstructures of both ADI and TM, separately. In the case of wear behavior, TM had the highest hardness and the lowest friction coefficient among the three irons. The order of wear resistance was TM > ADI > DI. In the case of corrosion behavior in 3.5%NaCl solution, ADI had the best corrosion resistance due to with retained austenite in microstructure. The order of wear resistance was ADI > DI > TM....
摘要:In this paper, an experimental model for the directional solidification of Sn-Pb alloy is built and the effects of magnetic field and Pb concentration on the solidification morphology are investigated. According to the experimental results, from the microstructure observation, the casting can be divided into three zones, the chill zone, the columnar zone, and the equiaxed zone. In different Pb concentration, we observe that, lower Pb concentration has more point defect (microshrinkage etc.); G.B. didn't clear to be observed with OM. Eutectic Sn-Pb alloy is lamellar structure, dendrite didn't clear to be observed with OM. In the case of directional solidification with opposite attraction and cyclic magnetic fields, has coarser columnar structures than those of the one without magnetic field, but in the case of directional solidification with linear magnetic field, has thinner columnar structures than those of the one without magnetic field....
[期刊论文] Y. N. Pan B. L. Zheng
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2018年 2 TN.177期
摘要:While casting the A390 hypereutectic aluminum alloy, primary Si particles tend to float to the upper part of the casting due to the difference in specific weight between the primary Si particles and the aluminum bulk liquid, the so-called gravity segregation. As a result, the mechanical properties in different parts of the casting vary. Utilizing the above-mentioned phenomenon of the primary silicon gravity segregation, the present study further enhanced this segregation nature by employing centrifuging casting process to achieve better wear resistance in specific areas of the castings. A centrifuging casting apparatus was constructed which allows the casting to be solidified under the centrifugal force. Under the centrifuging casting condition, the primary silicon particles which have low specific gravity and high hardness tend to move toward the rotational axis and aggregate at the inner portion of the castings. By analyzing the microstructures of different parts of the casting under different pouring temperatures (780℃, 820℃) and rotational speeds (400 rpm, 450 rpm, … , 650 rpm), we concluded that the degree of primary silicon segregation toward the inner portion of the casting increases with increasing both pouring temperature and rotational speed, and reaches a plateau at 500 rpm. Therefore, a pouring temperature of 820℃ and a rotational speed of 500 rpm were chosen in this study. In addition, P refinement (for primary Si) and Sr modification (for eutectic Si) were performed to examine the effects of either P refinement or Sr modification on the microstructures of the centrifuging castings at 500 rpm. Further, the relationship between the microstructure features obtained and the wear resistance property was evaluated....
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2016年 2 TN.169期
摘要:Austempered ductile iron (ADI) possesses excellent mechanical properties, but there are numerous holes present on its surface due to nodules peeling. These holes limit the efficiency of ceramic coatings by PVD technology. Therefore, this study utilized electroless nickel (EN) as an interlayer with the various thicknesses (5μm, 15μm, 25μm) to fill the holes before PVD-TiN coating on ADI substrates. Two types of corrosion tests; polarization test and immersion test, were separately conducted in 3.5% NaCl and 20% H_2SO_4 corrosive media. The purpose is to explore the effect of interlayer thickness on the corrosion behavior of ADI. The experimental results show that the efficiency of filling holes increases with the increase of EN interlayer thickness. As a result, the composite coatings could evidently improve the corrosion resistance of ADI in both 3.5% NaCl and 20% H_2SO_4 solutions. In particular, an interlayer of 25μm EN between TiN coating and ADI substrate exhibits the best corrosion resistance....
[期刊论文] S. A. Lu Y. N. Pan
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2013年 3 TN.158期
摘要:The primary purposes of this research are threefold: (1) to study the effects of metallurgical and processing parameters on the formation of the abnormal structure on the skin of the thin-wall ductile iron castings, (2) to explore the mechanisms for the formation of the abnormal skin structure, and (3) to correlate the skin abnormal structure in terms of degraded area with the thermal fatigue life of the thin-wall ductile iron castings. Taguchi's analysis results indicate that among the three types of coating (graphite, SiO_2 and MgO) investigated, graphite coating exhibits the most effective when poured at a relatively high pouring temperature (1723°K(1450℃)), while SiO_2 is the most favorite coating for a relatively low pouring temperature (1673°K(1400℃)). Nevertheless, no significant difference in effectiveness on the prevention of the abnormal skin structure was observed among these three coatings, but MgO coating shows the least variations in the degraded area of the abnormal skin structure. Furthermore, significant improvement was obtained when a coating was applied as compared to the case of without coating. Regarding the thermal fatigue property, the thermal fatigue life increases with decreasing the degraded area of the abnormal skin structure. In addition, increased thermal fatigue life was registered for castings poured at a relatively higher temperature, i.e., 1723°K(1450℃), and with a thicker section, i.e., 6mm. Finally, the phenomenon of microstructure transformation and the failure mechanism during the cyclic thermal process were analyzed in this study....
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