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金属半固态加工技术的应用与进展 总被引:10,自引:0,他引:10
半固态加工技术具有高效、节能、近净形生产以及制成品显微组织细化均匀、力学性能好等诸多优点,是一种很有前途的加工方法。介绍了半固态加工的原理、特点,以及用于制备合金和复合材料的研究情况及应用前景等。 相似文献
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半固态专用铝合金AlSi6Mg2微合金化研究 总被引:3,自引:0,他引:3
半固态加工是一种新的近终成形技术,但由于缺乏适合发挥其优势的专用合金,使这项技术在工业中的推广应用受到了限制,针对这一现状开发新型铝合金AlSi6Mg2。利用电磁搅拌装置制备半固态浆料,探讨了微量合金化元素Ti,Sr对AlSi6Mg2半固态合金微观组织和力学性能的影响。结果显示,合金中Ti含量为0.08%左右时,能够细化初生相α(Al)基体;合金中Sr含量为0.02%~0.04%时,不仅能够改善共晶硅形貌,使其由板条状转化为点状或短簇状,而且对Mg2Si也有一定的变质作用,使合金的性能明显改善,特别是塑性提高了1倍以上。 相似文献
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1前言 半固态金属成形主要用于对铝合金和镁合金等轻金属的加工。到目前为止,半固态金属成形一直被用来制造此类合金的各种金属部件,如汽车和移动电话的配件。对于轻金属半固态成形的绝大多数研究的目的是为了揭示轻金属合金半固态成形实用技术发展的基本特征。相比之下,对包括不锈钢在内的铁基合金半固态成形的研究还非常少,这可能是由于此类合金具有较高的熔点、较窄的半固态温度区间以及在凝固和重熔过程中发生复杂的γ←→δ相变。对铁基合金半固态成形工艺进行优化需要了解其在半固态时的材料特性。这些特性在半固态温度区间内受到材料显微结构变化的显著影响。对于铁基合金半固态成形的研究仍处于基础阶段。 相似文献
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采用流变成型法制备了半固态ZA27—16Vol%Si合金,与常规铸造合金进行了对比,并对其摩擦特性进行了研究,为锌铝合金的半固态加工新技术提供了理论依据。 相似文献
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研究了AZ91D合金在半固态等温热处理过程中,等温温度和等温时间对其组织和力学性能的影响.结果表明:在本实验条件下,当等温热处理温度为585℃、等温时间90min时,AZ91D合金具有良好的组织形态和力学性能. 相似文献
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A Study of the Method of Manufacturing Bimaterial Composite Parts through Semisolid Metal Processing
Yang Zhao Dong Jianxiong Zhou Li Shen Li Zhang Wei 《Metallurgical and Materials Transactions A》2011,42(6):1709-1716
This work evaluated the method of manufacturing bimaterial composite parts by semisolid metal processing (SSP) through strain-induced
melt-activated thixo-forging. Sn-15 pct Pb and Pb-30 pct Sn semisolid alloys were chosen as model alloys. Bimetal composite
parts were manufactured successfully by forging the semisolid alloys into the same die simultaneously. Optical photography,
scanning electron microscopy, energy dispersive X-ray spectroscopy, and Vickers hardness were employed to characterize the
samples. The results showed that the composite semisolid fluid flowed in a laminar way. Globular primary grains in the two
semisolid alloys maintained their respective geometry and constitutions. The mixture of two liquid phases was limited in a
thin layer beneath the interface between the two semisolid alloys. The absence of an oxide-enriched layer at the interface
suggests that the oxide skins of the feedstock were torn during the processing, leading to the formation of metallurgical
bonding at the composite interface. This work showed that SSP is a promising technology for bimaterial/multimaterial composite
manufacturing. The bimaterial composite parts achieved by SSP have a good composite interface and well-located material distribution. 相似文献
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Q. Y. Pan D. Apelian A. N. Alexandrou 《Metallurgical and Materials Transactions B》2004,35(6):1187-1202
Systematic experimental work and modeling efforts have been conducted to characterize the yield behavior of commercial aluminum
alloys in the semisolid state. In this study, extensive compression experiments were performed to measure the yield stress
of semisolid aluminum slurries at high solid fractions (0.5 to 1.0), and a cone penetration method was employed to measure
yield stress at low solid fractions (<0.5). A functional relationship between yield stress and temperature/solid fraction
has been established for these alloys. The effect of the processing route on the resultant yield stress of the material in
the semisolid state was studied by evaluating commercial A356 billets manufactured via magnetohydrodynamic stirring, grain refining, and UBE’s new rheocasting (NRC) processes, respectively. Detailed microstructure
observations and image analyses reveal that the difference in yield-stress values among the alloys evaluated is intricately
related to the semisolid structure. At a given solid fraction, the yield stress of semisolid slurries depends on microstructural
indices (i.e., entrapped-liquid content, shape factor of the alpha phase, and the alpha particle size). In addition, numerical simulation
results indicate that the finite yield stress of semisolid metals plays a significant role in determining the flow pattern
during die filling. Depending on processing conditions, five distinct filling patterns (shell, disk, mound, bubble, and transition)
have been identified and confirmed through experimental observations. Recent simulations demonstrate that the finite yield
stress is also responsible for flow instabilities encountered in commercial forming operations, such as “toothpaste behavior.”
Specifically, most flow instabilities can be avoided by properly controlling processing parameters and the initial semisolid
microstructure. A stability map that provides a control guide for semisolid processing has been developed and is presented. 相似文献
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In this work the suitability of alloys for semi‐solid processing was investigated using numeric simulation. The simulation was based on equilibrium calculations, Scheil‐Gulliver calculations and, when necessary, diffusion simulations. For this purpose a new parameter was introduced in addition to the commonly used selection criteria. With the new parameter, the thixo ranges ΔT40–60 and ΔT20–40, the specific demands of the different semi‐solid processes thixocasting and thixoforging can be considered. On the basis of thermodynamic simulation, the conventional aluminium alloys A356, AA6082 and A319, the steels 100Cr6, HS6‐5‐2 and X210CrW12 and a number of experimental aluminium‐lithium based alloys were evaluated according to the selection criteria. The thermodynamic calculations showed a large sensitivity of the course of the solidification with respect to variations in the contents of the alloying elements. This shows the necessity of keeping a tight composition control on alloys for semi‐solid processing. For aluminium alloys in particular silicon has to be monitored closely and for steels carbon and chromium. 相似文献
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T. K. Nandy Rebecca M. Messing J. Wayne Jones Tresa M. Pollock D. M. Walukas R. F. Decker 《Metallurgical and Materials Transactions A》2006,37(12):3725-3736
A new procedure for blending die-cast Mg−Al alloys by semisolid processing to achieve controlled variations in microstructure
and properties has been investigated. Granules of AM6-B and AZ91D have been blended in varying proportions and Thixomolded
at nominal solid fractions of 0.1 and 0.3, respectively. As-molded microstructures and the role of interdifussion during processing
have been analyzed in detail by scanning electron microscopy, transmission electron microscopy, and electron microprobe analysis.
Tensile properties and failure modes have been analyzed and a strength model that considers solid solution strengthening of
Al in the unmelted particles and a rule-of-mixtures behavior for microstructural components is proposed. 相似文献
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Julio Aguilar Martin Fehlbier Tilman Grimmig Horst Bramann Carsten Afrath Andreas Bührig‐Polaczek 《国际钢铁研究》2004,75(8-9):492-505
Semi‐solid metal casting is an innovative technology for the production of near‐net‐shape parts with demanding mechanical properties. The paper describes different processing routes and materials for semi‐solid‐metal casting (SSM), which have been investigated and also partially developed at the Foundry‐Institute of Aachen University. The standard thixocasting process for aluminium, highly reactive magnesium alloys and steel alloys with high melting points was investigated under variation of a wide range of process parameters. Specially adapted pre‐material production and reheating methods were developed for different materials and their application and future potential is pointed out. The thixocasting experiments were executed on a modified high pressure die‐casting machine with a specially designed “step‐die” providing wall thicknesses from 0.5 to 25 mm. The mechanical properties were tested in dependence of the wall thickness and the metal velocity. The results of these examination show high tensile strength values in combination with very good elongations. The rheocasting process is a new SSM‐forming method with liquid melt as feed‐stock and a high recycling potential. The research results of RCP‐technology (Rheo‐Container‐Process) invented at the Foundry‐Institute and of the Cooling‐Channel‐Process for aluminium and magnesium alloys are promising and are presented in this paper. Studies on semi‐solid processing of magnesium alloys and mixtures of them were conducted by ThixomoldingTM. To establish the most adequate process parameters, the temperature and the mixture relations were varied. Using a mould for tensile test specimens, the mechanical properties and the microstructure evolution could be evaluated. The chemical composition of the different phases was determined using SEM and EDX technologies. Evaluations of the flowing properties were conducted using a spiral mould with a total length of 2m and a cross section of 20mm x 1.5mm. 相似文献
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An investigation has been made into the solidification behavior and microstructural evolution of AM50, AM70, and AM90 alloys
during rheo-diecasting, their processibility, and the resulting mechanical properties. It was found that solidification of
AM series alloys under intensive melt shearing in the unique twin-screw slurry maker during rheo-diecasting gave rise to numerous
spheroidal primary magnesium (Mg) particles that were uniformly present in the microstructure. As a result, the network of
the β-Mg17Al12 phase was consistently interrupted by these spheroidal and ductile particles. Such a microstructure reduced the obstacle
of deformation and the harmfulness of the β-Mg17Al12 network on ductility, and therefore improved the ductility of rheo-diecast AM alloys. It was shown that, even with 9 wt pct
Al, the elongation of rheo-diecast AM90 still achieved (9 ± 1.2) pct. Rheodiecasting thus provides an attractive processing
route for upgrading the alloy specification of AM series alloys by increasing the aluminum (Al) content while ensuring ductility.
Assessment of the processibility of AM series alloys for semisolid processing showed that high Al content AM series alloys
are more suitable for rheo-diecasting than low Al content alloys, because of the lower sensitivity of solid fraction to temperature,
the lower liquidus temperature, and the smaller interval between the semisolid processing temperature and the complete solidification
temperature. 相似文献
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D. Sohrabi Baba Heidary F. Akhlaghi 《Metallurgical and Materials Transactions A》2010,41(13):3435-3442
Determining the viscosity of low solid volume fraction semisolid alloys is important for predicting the gradient of primary
particles within functionally graded materials (FGMs), produced by in-situ casting processes. In this study, a new precise rotational viscometer was developed and used to measure the viscosity of
Al-22 pct Si and Al-30 pct Si semisolid alloys up to solid volume fractions of 9 and 20 pct, respectively. Three kinds of
typical curves, viscosity (η) vs solid volume fraction (f
s
), shear time (t), and shear rate ([(g)\dot] \dot{\gamma } ), were derived from the results of viscosity measurements for both Al-Si alloys. In the semisolid Al-Si alloys, thixotropic
behavior was not detected at low solid volume fractions, but this behavior was obviously observed with increasing solid volume
fraction and could be described by an analytical model. Finally, the results showed that the equilibrium viscosity of the
semisolid alloys with thixotropic properties decreased by increasing shear rate according to the Ostwald–De Waele power law.
A special test, developed in this research, was used to show the effect of agglomeration on the viscosity of the semisolid
alloys. 相似文献
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One important parameter for the processing of materials by semi‐solid forming is the actual distribution of the solid and liquid phases in the semi‐solid range. This parameter defines the process stability for the forming step. Therefore it is necessary to obtain information about the materials behaviour in the semi‐solid state for different materials grades. This kind of information can be obtained by experimental studies in the interesting temperature range or by calculations with simulation programs using thermodynamic data validated by experiments. This work shows the results of experimental studies and thermodynamic calculations of the solidification and heat treatment behaviour of the aluminium alloy A319 and the steel X210CrW12. The experimental studies of solidification and heat treatment of these alloys were carried out using a differential thermal analysis system (DTA). The theoretical fraction of liquid content was calculated from the DTA signal by using a software module called Corrdsc. The experimental data obtained were used to validate the thermodynamic simulations of the solidification of semi‐solid alloys. The simulations of the solidification process were carried out for equilibrium conditions, with the Scheil‐Gulliver model as well as with diffusion calculations. The equilibrium and Scheil‐Gulliver calculations were performed by the program Thermo‐Calc, and the diffusion by the program DICTRA. The required thermodynamic and mobility data for multicomponent systems were taken from the data bases COST 507 light alloys, TCFE2000 Steel/Alloys and MOB2 mobility and from newly added data. The comparison of calculated phase transformations and fractions of liquid content with experimental data revealed a good agreement. 相似文献