共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
3.
The density and surface tension of liquid Fe-Mn alloys were determined by using the sessile drop method at 1823 K (1550 °C).
The density of liquid Fe-Mn alloys decreased with increasing Mn content. When the molar volume was plotted with respect to
the mole fraction of Mn, a linear relationship was obtained. Consequently, it was found that there is no excess volume in
liquid Fe-Mn alloy. The surface tension of liquid Fe-Mn alloys was found to decrease with increasing Mn content. The current
experimental data were higher than the reported results but close to the calculated results using Butler’s equation. 相似文献
4.
Abbas A. Khalaf Peyman Ashtari Sumanth Shankar 《Metallurgical and Materials Transactions B》2009,40(6):843-849
Controlled diffusion solidification (CDS) is a novel process wherein specific Al alloys can be cast by mixing two precursor
alloys of specific compositions and temperature and subsequently casting the resultant mixture. This process enables a nondendritic
morphology of the primary Al phase in the cast samples, which is beneficial in mitigating hot tearing tendencies and enabling
castability of dilute Al (wrought) alloys to obtain castings with superior mechanical and performance properties. In this
study, a hypothesis is proposed to describe the mechanism of the CDS process, specifically the processes of mixing two precursor
alloys and a subsequent solidification process. Al – 4.5 wt pct Cu was used as an example alloy system to propose a hypothesis
and to verify the various features in the mechanism of mixing two alloys. Experimental results show that the mixing process
naturally causes copious nucleation of one of the alloys mixed and that the turbulence energy during mixing distributes these
nuclei uniformly to enable a favorable solidification condition for a nondendritic cast microstructure. It is critical that
the alloy with the higher thermal mass (mass and temperature) is mixed into the alloy with lower thermal mass to obtain a
valid CDS process and that the reverse will not yield a favorable homogeneous cast sample. Certain critical parameters during
the CDS process have also been identified and quantified for a favorable microstructure of the casting. 相似文献
5.
William Yi Wang Shun Li Shang Hua Zhi Fang Hui Zhang Yi Wang Suveen Nigel Mathaudhu Xi Dong Hui Zi-Kui Liu 《Metallurgical and Materials Transactions A》2012,43(10):3471-3480
The diffusion coefficients and viscosity of four Al1?Cx Zr x (x?=?0.4, 0.5. 0.6, and 0.67) alloys are predicted by ab initio molecular dynamic simulations via the Einstein and Darken equations. It is observed that the addition of Zr to Al reduces the self-diffusion coefficient of Al drastically, whereas the addition of Al to Zr has little effect on the self-diffusion coefficient of Zr. The interdiffusion coefficient and viscosity are predicted with both being close to those of pure Al extrapolated to high temperatures. Based on the analysis of atomic structures, the observations are attributed to clustering in liquid so that the migration of Al and Zr are correlated strongly and viscous flow is affected by Al-Al bonding between clusters. 相似文献
6.
7.
8.
S. N. Tewari R. N. Grugel D. R. Poirier 《Metallurgical and Materials Transactions A》2014,45(11):4758-4761
The primary dendrite trunk diameters of Al-Si alloys that were directionally solidified over a range of processing conditions have been evaluated. The empirical data are analyzed with a model that is an extension of one used to describe the ripening of dendrite arms. The analysis, based primarily on an assessment of secondary dendrite arm dissolution in the mushy zone, fits well with the experimental data. It is suggested that the primary dendrite trunk diameter is a useful metric that correlates well with the actual solidification processing parameters, and complements the conventionally used primary, secondary, and tertiary arm spacings. 相似文献
9.
Uludağ Muhammet Çetin Remzi Dispinar Derya 《Metallurgical and Materials Transactions A》2018,49(5):1948-1961
Metallurgical and Materials Transactions A - In this study, three different aluminum-silicon alloys (A356, A413, and A380) that have different solidification morphology and solidification ranges... 相似文献
10.
11.
以NH1CI溶液和Al-1.65%Si合金为研究对象,探讨了液面振荡条件下强冷对等轴晶形成的影响.试验结果表明:利用强冷与液面振荡结合,可使NH4CI溶液结晶变得细小;对于Al-Si合金来说,铸锭底部强冷促进等轴晶的形成.强冷与液面振荡结合增加了等轴晶的数量.对等轴晶的形成有一定的贡献作用. 相似文献
12.
13.
Ab-initio density functional theory (DFT) calculations were performed to study alloying effects on hcp Mg. The alloy solid solution strengthening represented by bond strength enhancement in alloys, elastic properties, thermal expansion coefficients, and electronic structures of Mg-based alloys was investigated. Results show that alloying additions with sp-metal Al and rare earth (RE) Y are capable of increasing the bond strength, with the addition of Y achieving a better effect. The bond strength enhancement due to an RE Y addition is associated with a hybridization between the d-orbital of Y and the p-orbital of the Mg atoms near the Fermi energy, and this was consistent with the electron localized function (ELF) evaluations showing that more localized and stronger covalent bonds are formed between Y and Mg atoms. It is also found that alloying additions of Al, Zn, and Y are not capable of increasing elastic coefficients and moduli, indicating that bond strength enhancement could play a major role in alloy solid solution strengthening in Mg-based alloys. Possible reasons for the elastic properties accompanying the alloying addition are given from the electronic point of view. Furthermore, from the calculated negative Cauchy pressure (C 13 – C 44 < 0), it is concluded that the chemical bonds between Y and Mg atoms show angular characteristics. 相似文献
14.
The nucleation and growth behaviors of primary Al phase in two hypoeutectic binary alloys of Al-20.8%Cu and Al-3%Ni in high static magnetic fields were investigated with aid of differential thermal analysis(DTA).The DTA curves indicated that the nucleation temperature of primary crystals in two alloys decreased with increase of the magnetic field intensity and their nucleation was retarded in the magnetic field.The dendrite morphology showed that primary dendrites grew from disorderly without the magnetic field to regularly with the field.The retardation of nucleation of primary Al crystals was mainly caused by increase of interracial free energy.The change in dendrite morphology could be attributed to suppression of melt flows in the magnetic field. 相似文献
15.
稀土在Al-Si合金中的分布及其对变质过程的影响 总被引:3,自引:0,他引:3
通过俄歇微探针定点成分分析和X射线粉末照像方法,分别对稀土在初生Si颗粒和共晶组织两相中的存在和分布特点进行了研究。结果表明:稀土变质剂使初生Si颗粒由开花状板片变成多面体颗粒状。产生这种变化的原因是与稀土吸附并阻碍Si相沿挛晶凹坑的生长有关;在AI-Si合金中,微量稀土主要存在于Si相,在Si相中分布较均匀,未发现选择性吸附和明显的浓度偏聚;微量稀土变质剂没有明显的形成化合物,不形成Si相的异质核心。 相似文献
16.
17.
Martin Halmann 《Mineral Processing and Extractive Metallurgy Review》2013,34(2):106-116
Examination of the thermodynamic constraints for the carbothermic reduction of iron-free kaolinite, Al2Si2O5(OH)4, or of its calcination product mullite, Al6Si2O13, either at atmospheric pressure or under vacuum of 10?3 to 10?5 bar, indicates the conditions required at equilibrium to produce either elementary Al or Al-Si alloys. At atmospheric pressure, a very high temperature of 3200 K would be required to obtain from Al2Si2O5(OH)4 + 9C an Al-Si alloy with 39 wt.% Si. At 10?4 bar and 1800 K, the predicted Al-Si alloy would contain 2.4 wt.% Si. From mullite, the reaction of Al6Si2O13 + 13C at 10?4 bar and either 1800 K or 2200 K should produce an Al-Si alloy with 0.65 or 24 wt.% Si. The CO produced by the carbothermic reactions may be by water-gas shift converted to syngas, and further either to methanol or by a Fischer–Tropsch reaction to liquid fuels or chemical intermediates. Concentrated solar energy may be used to supply the required process heat of these high-temperature reactions. 相似文献
18.
L. G. Hou H. Yu H. Cui Y. H. Cai L. Z. Zhuang J. S. Zhang 《Metallurgical and Materials Transactions A》2013,44(4):1814-1826
Based on the densification of the spray-formed hypereutectic Al-Si (hyper-AS) alloys, the microstructural evolution, mechanical properties, as well as the failure are studied in this investigation. The appropriate process and parameters for the densification of the deposits are gained from the thermomechanical simulation. Besides of the spray-formed Al-25Si-5Fe-3Cu (3C) alloy, the microstructures of other spray-formed alloys with Mn/Cr addition are stable without coarsening of the refined α-Al(Fe,TM)Si (TM = Mn/Cr/(Mn+Cr)) particles, which can improve the heat resistance. Especially, a great number of the submicrosized α-Al(Fe,TM)Si phases are observed in the hot-extruded TM-containing alloys. The critical ranges of the major parameter TM/Fe mass ratios that can affect the formation of the α-Al(Fe,TM)Si phases in the cast or spray-formed hyper-AS alloys are severally determined. The structure and lattice constant of the refined α-Al(Fe,TM)Si phases also are characterized. The mechanical properties of the current extruded hyper-AS alloys at room or elevated temperatures are close to or higher than some commercial alloys or other published results. Therefore, the hyper-AS alloys can be proposed as new lightweight, heat-resistant, and high-strength alloys, which can be used in the complex working conditions, such as advanced engine systems. The main reason for the enhanced properties would be the formation of a large quantity of microsized/submicrosized α-Al(Fe,TM)Si phases and abundant dislocations, which can greatly reinforce the matrix and transform the brittle fracture of the needle-like Fe-bearing phases into ductile fracture. 相似文献
19.
Mohammad Ammar Mofid Amir Abdollah-Zadeh Farshid Malek Ghaini Cemil Hakan Gür 《Metallurgical and Materials Transactions A》2012,43(13):5106-5114
Submerged friction-stir welding (SFSW) underwater and under liquid nitrogen is demonstrated as an alternative and improved method for creating fine-grained welds in dissimilar metals. Plates of AZ31 (Mg alloy) and AA5083 H34 were joined by friction-stir welding in three different environments, i.e., in air, water, and liquid nitrogen at 400?rpm and 50?mm/min. The temperature profile, microstructure, scanning electron microscopy (SEM)-energy-dispersive spectroscopy (EDS) analysis, X-ray diffraction (XRD), hardness, and tensile testing results were evaluated. In the stir zone of an air-welded specimen, formation of brittle intermetallic compounds of Al3Mg2, Al12Mg17, and Al2Mg3 contributed to cracking in the weld nugget. These phases were formed because of constitutional liquation. Friction-stir welding underwater and under liquid nitrogen significantly suppresses the formation of intermetallic compounds because of the lower peak temperature. Furthermore, the temperature profiles plotted during this investigation indicate that the largest amount of ?T is generated by the weld under liquid nitrogen, which is performed at the lowest temperature. It is shown that in low-temperature FSW, the flow stress is higher, plastic contribution increases, and so adiabatic heating, a result of high strain and high strain-rate deformation, drives the recrystallization process beside frictional heat. 相似文献
20.
Wessing Johanna Jeanette Brillo Jürgen 《Metallurgical and Materials Transactions A》2017,48(2):868-882
Metallurgical and Materials Transactions A - Al-Ti-based alloys are of enormous technical relevance due to their specific properties. For studies in atomic dynamics, surface physics and industrial... 相似文献