共查询到20条相似文献,搜索用时 31 毫秒
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Electropulse modification (EPM) process, a new physical field method for improving the solidification structure of metals was introduced.Different from other research, EPM is only acting pulse current on melt under liquid state.The solidification structure of Al-Si alloys, A1-Cu alloys,cast iron and steel can be modified obviously with this method: the solidification structure of ZL101 alloy presented the Na and Sr modification and the mechanical properties were enhanced; a large number of primary silicon appeared in the microstructure of ZL109 alloy; the equiaxed grain zone was expanded and the grains were fined in Al-5.0wt% Cu alloy; the graphitization took place in solidification process of molten cast iron; the grain sizes of solidification structure of T8 steel were reduced significantly and the shape of steel pearlites also changed; the equiaxed grain zone increased to 88% from original untreated 19%, the equiaxed grains were fined and the intercrystalline crack was avoided in concasting billet by continuously treating liquid electrical sheet steel in tundish.Effects of rare earths on casting Al-Si alloys were also summarized.The method of modifying the solidification structure of rare earth Al-Si alloys with EPM in producing the alloys was proposed. 相似文献
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采用常规铸造和分段式倾斜板过流冷却铸造工艺制备Al-22Si-2Fe-xMn合金,研究表明:过流冷却制备工艺能够改善初生Si形貌及尺寸,但对针状富Fe相作用有限.利用扫描电镜、X射线衍射及透射电镜等手段分析过流冷却条件下Mn元素添加对富Fe相晶体结构的影响,通过摩擦磨损实验研究不同Mn/Fe质量比的过共晶Al-Si合金的硬度及耐磨损性能.结果表明:随着过流冷却铸造过共晶Al-Si合金中Mn/Fe质量比增加,合金中四方结构的长针状富Fe相逐渐减少直至基本消失,当Mn/Fe质量比为0.7时,富Fe相主要为六方结构的块状或鱼骨状α-Al15(Fe,Mn)3Si2相,此时,合金耐磨性较未添加Mn元素时有所提升,磨损机制以磨料磨损方式为主. 相似文献
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含铝50%的硅铝合金生产技术 总被引:1,自引:0,他引:1
通过对冶炼硅铝合金的理论分析,结合国外生产的工艺技术,提出了解决我国冶炼硅铝合金的技术难题。指出矿热炉冶炼含铝50%的硅铝合金是可行的。 相似文献
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David R. Poirier 《Metallurgical and Materials Transactions B》2014,45(4):1345-1354
This article is a review of empirical and calculated data on density, viscosity, and diffusion coefficients in hypereutectic Al-Si liquid alloys. Many regressions of the data were effected in order to consolidate the data as functions, which can be used to calculate each property as a function of temperature and concentration of Si. The chemical diffusion coefficient in the alloys was derived based on the Sutherland model, which relates the diffusion coefficient to viscosity. 相似文献
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Thomas Hartmut Ludwig Paul Louis Schaffer Lars Arnberg 《Metallurgical and Materials Transactions A》2013,44(13):5796-5805
The role of phosphorus (P) in the heterogeneous nucleation of eutectic silicon (Si) and the evolution of eutectic grains in hypoeutectic aluminum-silicon alloys were investigated. Systematic additions of P in the range of 0.5 to 20 ppm to Al-7 wt pct Si alloys of different purities have shown that the morphology of the eutectic Si changes from a fine plate- to a coarse flake-like structure. The growth of eutectic grains was investigated by interrupting the eutectic reaction by quenching experiments. Moreover, the macroscopic growth mode of the eutectic grains was characterized by electron backscatter diffraction. An increase in P concentration from 2 to 3 ppm resulted in a transition of the macroscopic growth mode of the Al-Si eutectic in high purity alloys from growth with a planar front with a strong dependence of the thermal gradient, to nucleation in the vicinity of the primary Al dendrites and subsequent growth of distinct eutectic grains. It is suggested that AlP particles are the key impurities acting as potential nucleation sites for eutectic Si. This is further substantiated as with increasing P concentration nucleation and growth of the Al-Si occurred at higher temperatures close the equilibrium Al-Si eutectic solidification temperature at 850 K (577 °C). In addition, the recalescence undercooling ΔT R,eu was reduced from 4.5 K (0.5 ppm P) to 1.5 K (20 ppm P) in high purity alloys. This was accompanied by a drastic increase of the nucleation rate of the eutectic grains. 相似文献
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《粉末冶金学》2013,56(2):159-164
AbstractThe effects of warm compaction on the green density and sintering behaviour of aluminium alloys were investigated. Particular attention is paid to prealloyed powders, i.e. eutectic and hypereutectic Al-Si alloys, regarding their potential applications in the automotive industry. The effects of chemical composition, alloying method, compacting temperature and the amount of powder lubricant were studied. The compaction behaviour was examined by an instrumented die enabling simultaneous measurement of density, die wall friction coefficient, the triaxial stresses acting on the powder during the course of compaction and ejection pressure. The sintering behaviour was studied via dilatometeric analysis as well as normal batch sintering. The results show that warm compaction could be a promising way to increase the green density of aluminium alloys, especially prealloyed powders, and to decreased imensional instability during sintering. Moreover, it reduces the sliding friction coefficient and the ejection force during the powder shaping process. This paper presents the significant advantages and drawbacks of using the warm compaction process for commercial PM aluminium alloys. 相似文献
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Al—3B中间合金的加工量对亚共晶Al—Si合金晶粒细化的影响 总被引:3,自引:0,他引:3
研究了Al-3B中间合金不同的加入量对亚共晶Al-Si合金晶粒尺寸的影响。该中间合金对所研究全部范围内的Al-Si合金都具有一定的细化效果,但在不同的含硅量下其细化能力并不相同,同时证实对未经细化处理的亚共晶Al-Si合金而言,在含硅量约3%(质量分数,下同)时合金具有最小的晶粒尺寸。随着Al-3B中间合金加入量的提高,出现最小晶粒尺寸的合成成分向高硅方向移动,当加入量达到1%时,在含硅量为6%的Al-Si合金中出现最小的晶粒尺寸。 相似文献
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G. A. Bagluyk S. G. Napara-Volgina A. A. Mamonova L. N. Orlova V. K. Kud’ 《Russian Journal of Non-Ferrous Metals》2012,53(5):425-428
Results from investigating the effect of technological conditions for the synthesis of powdered boron-containing foundry alloys on their chemical and phase compositions and the content of foundry alloys in the charge on the structure and properties of sintered steels fabricated using them are presented. It is shown that using denser briquettes obtained at a pressure of ??700 MPa allows us to reduce substantially boron evaporation through the gas phase during the synthesis of foundry alloys, relative to briquettes compacted at lower pressures. Using an elevated foundry alloy synthesis temperature (1200°C) leads to higher density of the post-sintered material, and thus to enhanced strength characteristics. Increasing the boron content in the initial charge increases the hardness and lowers the strength of sintered steels, while the curve of the strength??s dependence on the boron content after thermal treatment peaks at ??0.8% B. 相似文献
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K. V. Nikitin A. B. Finkel’shtein O. A. Chikova I. Yu. Timoshkin 《Russian Journal of Non-Ferrous Metals》2013,54(4):314-319
The influence of the structure of starting charge alloys Al-20 wt % Si on their structure after single remelting and crystallization with an identical cooling rate of 20 K/s is investigated. It is established that the structural transformation from the starting charge alloys stably retains, being translated in the “solid-liquid-solid” system. The viscosimetry investigation of the melts obtained from the coarse-crystalline and the fine-crystalline charge alloys in the heating mode to 1350°C and the subsequent cooling confirmed the conclusion that these melts are translators of structural information. It is established that the branching temperature (hysteresis) of viscosity polytherms (t h) in the heating and cooling modes for the melt made from the coarse-crystalline charge alloy is 1100°C, while that for the fine-crystalline charge alloy is 1000°C. It is noted that, in the second case, the viscosity in the cooling mode below t h is elevated, while the polythermal branch ascends more steeply. These results indicate the favorability of using special methods of processing the charge metals with the goal of laying positive structural information into them. The use of this approach is most reasonable when obtaining aluminum-based foundry alloys. 相似文献
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K. R. Ravi S. Manivannan G. Phanikumar B. S. Murty Suresh Sundarraj 《Metallurgical and Materials Transactions A》2011,42(7):2028-2039
Although the grain-refinement practice is well established for wrought Al alloys, in the case of foundry alloys such as near
eutectic Al-Si alloys, the underlying mechanisms and the use of grain refiners need better understanding. Conventional grain
refiners such as Al-5Ti-1B are not effective in grain refining the Al-Si alloys due to the poisoning effect of Si. In this
work, we report the results of a newly developed grain refiner, which can effectively grain refine as well as modify eutectic
and primary Si in near eutectic Al-Si alloys. Among the material choices, the grain refining response with Al-1Ti-3B master
alloy is found to be superior compared to the conventional Al-5Ti-1B master alloy. It was also found that magnesium additions
of 0.2 wt pct along with the Al-1Ti-3B master alloy further enhance the near eutectic Al-Si alloy’s grain refining efficiency,
thus leading to improved bulk mechanical properties. We have found that magnesium essentially scavenges the oxygen present
on the surface of nucleant particles, improves wettability, and reduces the agglomeration tendency of boride particles, thereby
enhancing grain refining efficiency. It allows the nucleant particles to act as potent and active nucleation sites even at
levels as low as 0.2 pct in the Al-1Ti-3B master alloy. 相似文献
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The effects of microstructure on the erosion of Al-Si alloys by 40 μm Al2O3 particles were investigated. The impact angle dependence of the erosion rate of Al and the Al-Si alloys exhibited the ductile signature, whereas that for pure Si showed the brittle signature. The eroded surface of pure Al was characterized by craters, lips, overlaps and folds, and platelets; that for pure Si exhibited complex radial and lateral cracking at the impact site. At shallow impact angles these features were elongated in the direction of the tangential component of the velocity in both materials. The measured erosion rates of the Al-Si alloys were found to be in accord with an inverse rule of mixtures based on pure Al and pure Si; better agreement was, however, obtained if pure Al and the eutectic were taken as the two constituents for the hypoeutectic alloys, and pure Si and the eutectic for the hypereutectic alloys. The microstructure size had two effects: (a) scaling with respect to the impact damage zone size and (b) an influence on the physical and mechanical properties which govern material removal. The present results are considered in terms of current models for the erosion of ductile and brittle materials. 相似文献
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合金化Cr优化含Fe过共晶Al-Si合金显微组织及其机制 总被引:1,自引:1,他引:0
采用传统铸造工艺和喷射成形技术制备了无Cr和含Cr的含Fe过共晶Al-Si合金,并利用SEM(EDS)、XRD及DSC对其显微组织、相组成及相变过程进行了研究。结果表明:2%Cr的加入不光使铸态粗大针片状的δ-Al4FeSi2相变为"骨骼状"α-Al(Fe,Cr)Si相,而且使沉积态Al-25Si-5Fe-3Cu合金中短棒状的富铁相(~10μm左右)被尺寸小于3~5μm的颗粒状α-Al(Fe,Cr)Si相所替代,从而细化的组织更有利于合金性能的提高。等温处理实验结果显示沉积态含Cr合金具有较好的组织热稳定性,其主要归因于颗粒状α-Al(Fe,Cr)Si相自身的高温稳定性,而沉积态Al-25Si-5Fe-3Cu合金热稳定差主要由于β-Al5FeSi相的长大和A7Cu2Fe相的形成。另外,结合显微组织和喷射成形工艺特点对沉积态组织形成机制分析发现α-Al(Fe,Cr)Si相有可能通过直接从液相析出和经δ-Al(Fe,Cr)Si相转变而来。 相似文献
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现代霍尔-埃鲁特(H-H)法铝电解槽规模大、工艺成熟, 利用该法电解制备铝基合金具有明显技术和经济优势. 目前国内外研究主要是在现有氟化物熔盐体系中添加多种合金元素氧化物, 合理调节电解质成分和工艺参数, 借助共电沉积和欠电位机制, 成功制备出多种铝基合金, 工业化试验亦有初步成果. 本文综合分析了上述进展及发展前景, 并指出在实现合金组成精准调控、合金产品成分均匀化、电解槽高电流效率运行等方面存在的问题, 旨在为相关研究提供参考. 相似文献
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分析研究了Al—10Ce中间合金对ZL102共晶铝硅合金的变质处理效果。结果表明,Al—10Ce中间合金用量、熔体中的杂质以及冷却速度对变质效果的影响很大,Al-10Ce中间合金用量为0.9%左右时达到最佳变质效果,提高Al—Si的纯度可以获得变质组织,冷却速度超过70℃/min时才具有明显的变质效果。 相似文献
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The effects of microstructure on the erosion of Al-Si alloys by 40 μm Al2O3 particles were investigated. The impact angle dependence of the erosion rate of Al and the Al-Si alloys exhibited the ductile
signature, whereas that for pure Si showed the brittle signature. The eroded surface of pure Al was characterized by craters,
lips, overlaps and folds, and platelets; that for pure Si exhibited complex radial and lateral cracking at the impact site.
At shallow impact angles these features were elongated in the direction of the tangential component of the velocity in both
materials. The measured erosion rates of the Al-Si alloys were found to be in accord with an inverse rule of mixtures based
on pure Al and pure Si; better agreement was, however, obtained if pure Al and the eutectic were taken as the two constituents
for the hypoeutectic alloys, and pure Si and the eutectic for the hypereutectic alloys. The microstructure size had two effects:
(a) scaling with respect to the impact damage zone size and (b) an influence on the physical and mechanical properties which
govern material removal. The present results are considered in terms of current models for the erosion of ductile and brittle
materials.
Formerly with the Department of Materials Engineering,
Formerly with the Department of Materials Engineering, 相似文献
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《Acta Metallurgica Materialia》1995,43(8):3061-3073
The sessile drop technique was used to study the wetting behaviour of Al-Si alloys on SiC sintered ceramic substrates under vacuum in the 700–1100°C temperature interval. Al-Si alloys with Si concentrations up to 50% were tested. An expected non-wetting/wetting transition was observed at 900–1000°C due to the presence of an alumina film surrounding the molten alloy. At higher temperatures wetting was observed and the Si concentration of the alloy has a marked effect on the measured contact angles, θ. At 1100°C θ decreases from 55° to 25° when instead of pure al and A112.3%Si or an A116.6%Si alloy is used. The suppression of the formation of a continuous Al4C3 layer at the interface and a process of dissolution and reconstruction of the SiC surface, due to the increased Si concentration of the Al-Si alloys, are the key factors to explain the observed behaviour. 相似文献