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M. F. Zhu C. P. Hong D. M. Stefanescu Y. A. Chang 《Metallurgical and Materials Transactions B》2007,38(4):517-524
In this article, a front tracking (FT) model and a modified cellular automaton (MCA) model are presented and their capabilities
in modeling the microstructure evolution during solidification of aluminum alloys are demonstrated. The FT model is first
validated by comparison with the predictions of the Lipton–Glicksman–Kurz (LGK) model. Calculations of the steady-state dendritic
tip growth velocity and equilibrium liquid composition as a function of melt undercooling for an Al-4 wt pct Cu alloy exhibit
good agreement between the FT simulations and the LGK predictions. The FT model is also used to simulate the secondary dendrite
arm spacing as a function of local solidification time. The simulated results agree well with the experimental data. The MCA
model is applied to simulate dendritic and nondendritic microstructure evolution in semisolid processing of an Al-Si alloy.
The effect of fluid flow on dendritic growth is also examined. The solute profiles in equiaxed dendritic solidification of
a ternary aluminum alloy are simulated as a function of cooling rate and compared with the prediction of the Scheil model.
The MCA model is extended to the multiphase system for the simulation of eutectic solidification. A particular emphasis is
made on the quantitative aspects of simulations.
This article is based on a presentation made in the symposium ”Simulation of Aluminum Shape Casting Processing: From Design
to Mechanical Properties,” which occurred March 12–16, 2006, during the TMS Spring Meeting in San Antonio, Texas, under the
auspices of the Computational Materials Science and Engineering Committee, the Process Modeling, Analysis and Control Committee,
the Solidification Committee, the Mechanical Behavior of Materials Committee, and the Light Metal Division/Aluminum Committee. 相似文献
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Ang Zhang Jinglian Du Xiaopeng Zhang Zhipeng Guo Qigui Wang Shoumei Xiong 《Metallurgical and Materials Transactions A》2020,51(3):1023-1037
Simulation of the solid–liquid–gas interaction during solidification is challenging due to the presence of complex phase interfaces, bubble deformation, and high liquid/gas density ratio. In this work, a hybrid phase-field lattice-Boltzmann (PFLB) approach, together with a parallel and adaptive-mesh-refinement (Para-AMR) algorithm, is developed to model interactions between the gas bubble and solid growth front during solidification. The solid growth and bubble evolution are solved by the phase-field method. Both melt flow and bubble movement are determined by a kinetic-based lattice-Boltzmann model. Bubble dynamics during alloy solidification is modeled and compared with experiments, and a good agreement is achieved for various solid/liquid interfaces including planar, cellular, and dendritic interfaces. Results show that the effect of the bubble on solid array is dependent on the solid/liquid interface morphology, bubble size, and relative position between the bubble center and dendritic tip. Two interaction mechanisms, including engulfment and entrapment, are compared, and the difference is caused mainly by the redistribution of solute. The interaction mechanism between the rising multibubbles with large deformation and the dendritic array is also discussed. 相似文献
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采用金相显微镜(OM)及扫描电镜(SEM)对2D70铝合金的半连续铸锭的不同位置铸态凝固组织及其热形变后的组织进行了观察,并采用X射线衍射物相分析(XRD),能谱分析仪(EDS)对合金在凝固过程中的形成相进行了分析,对经过不同热形变工艺及淬火时效处理后的棒材进行了力学性能检测。结果表明,2D70铝合金凝固组织为典型枝晶结构,铸锭从心部到外部晶粒逐渐变细小,等轴倾向逐渐增加,沿晶界析出物逐渐增加。典型铸态组织为α(Al)、灰色蜂窝状S(Al2CuMg)、褐色针状Al7Cu2Fe和棕色条状或片状Al9FeNi相。与直接挤压工艺相比,采用先锻后挤大变形工艺后的组织均匀,化合物破碎严重,为进一步热处理和压力加工提供了良好的条件。先锻后挤工艺棒材最终抗拉强度和断后延伸率高于直接挤压棒材。屈服强度峰时效前先锻后挤的低于直接挤压的,而峰失效后前者高于后者。两种变形工艺棒材的分别于时效23和20 h达到强度峰值,先锻后挤工艺棒材的峰时效时抗拉强度、屈服强度、延伸率分别为453 MPa,390 MPa和12%。 相似文献
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铁素体不锈钢凝固过程中形成的柱状晶会影响钢的成形性,减少甚至避免铸坯柱状晶的形成,促进等轴晶的形成,对铁素体不锈钢来说尤为重要。采用连铸和模铸的试验方法浇铸了铁素体不锈钢430,以分析影响其凝固结构的因素。结果表明,电磁搅拌对430不锈钢连铸坯等轴晶的形成作用显著。无论模铸试验还是连铸试验,冷却强度对430铸坯柱状晶的形成都有明显的影响。在模铸试验条件下,碳、氮含量越高,越有利于其凝固时等轴晶的形成;在连铸试验条件下,由于温度梯度大,碳、氮含量对凝固组织的影响被削弱,但如果对钢液进行搅拌,碳、氮含量的变化对凝固组织仍然有明显的影响。 相似文献
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《钢铁研究学报(英文版)》2011,(Z2):371-376
The solidification structure was simulated by the commercial software CALCOSOFT under the real cooling condition during the continuous casting processes in this paper. The cellular automation-finite element model (CA-FE) was applied to simulate the microstructure of the slab, and the results were compared with the actual macrostructure. The results of microstructure simulated were in good agreement with that detected in the slabs. In addition, the solidification structure under different secondary cooling intensity was simulated. The results show that when specific water flows increase, the average grain surface area reduces, and columnar grains have the tendency to be longer. 相似文献
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The high temperature properties of steels depend on the solidification parameters and the formation parameters of manganese sulphide precipitates. Therefore, the occurrence of MnS precipitations in relation to primary and secondary microstructures was studied for different steel grades with a primary delta‐ferritic solidification or a primary austenitic solidification. The liquidus and solidus temperatures as well as the δ‐γ‐transformation temperature were calculated thermodynamically and measured by a DTA analysis in order to describe the solidification and transformation temperature range. The MnS formation temperature was calculated thermodynamically and compared to the results of SEM/EDX investigations on fracture surfaces of hot tensile specimens torn at different temperatures after in situ melting and controlled solidification. A special focus of these investigations was the location of MnS precipitates in relation to the primary and secondary grain boundaries. To explain the results, calculations were carried out taking into account the supersaturation of manganese and sulphur during the solidification in residual melt on the primary grain boundaries. 相似文献
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Herein, a 3D mathematical model is established to elucidate the meniscus solidification and heat transfer in the chamfered mold. The fluid flow, heat transfer, the solidification of steel, the oscillation of the mold, and the steel–slag interfacial tension are considered, and the meniscus behavior on different longitudinal sections and cross sections is discussed. Under the influence of the upper roll flow, the height of the steel level increases from submerged entry nozzle to narrow face, which affects the distribution of the oscillation mark on the surface of the shell. With the mold chamfer and two new corners, the thickness of the slag film at the corner 1 with angle of 123.7° is the largest, and the shell thickness is the smallest, which is related to the 3D profile of the meniscus near the corner. The largest heat flux is located at 10–14 mm below the initial level of liquid steel and is below 3.0 MW m−2. The heat flux at the corner 1 with small obtuse angle is the smallest on the same cross section, indicating that small obtuse angle near the corner resulted in the low heat transfer. 相似文献
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激光熔敷合金层的组织结构和凝固过程 总被引:6,自引:0,他引:6
运用SEM,X射线衍射仪,TEM等先进设备,对不同成分合金激光熔敷层到基体显微组织形貌的连续变化,熔敷层的相结构,取向关系和微观缺陷进行了深入系统的研究,根据试验结果和凝固理论,探讨了激光熔敷层的凝固过程,研究结果可以作为激光熔敷技术深入研究和发展的参考。 相似文献
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Alan A. Luo Penghuai Fu Liming Peng Xiaoyu Kang Zhenzhen Li Tianyu Zhu 《Metallurgical and Materials Transactions A》2012,43(1):360-368
The solidification microstructure and mechanical properties of as-cast Mg-Al-Sn alloys have been investigated using computational
thermodynamics and experiments. The as-cast microstructure of Mg-Al-Sn alloys consists of α-Mg, Mg17Al12, and Mg2Sn phases. The amount of Mg17Al12 and Mg2Sn phases formed increases with increasing Al and Sn content and shows good agreement between the experimental results and
the Scheil solidification calculations. Generally, the yield strength of as-cast alloys increases with Al and Sn content,
whereas the ductility decreases. This study has confirmed an early development of Mg-7Al-2Sn alloy for structural applications
and has led to a promising new Mg-7Al-5Sn alloy with significantly improved strength and ductility comparable with commercial
AZ91 alloy. 相似文献
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运用电阻法和DSC热分析发现了CuSn30%合金熔体中存在不可逆的结构转变。在转变区间前后,通过熔体过热处理手段探索了这一结构变化对合金凝固过程及凝固组织的影响。结果表明,不可逆熔体结构的变化导致熔体凝固所需的过冷度增大,合金凝固组织变化明显,初生相和共析组织细化,分布弥散化。并从熔体结构转变角度对上述现象的作用机理进行了分析探讨。 相似文献
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This article gives an overview of the strategy followed nowadays to model the evolution of metallic alloy microstructures
under irradiation. For this purpose, multiscale approaches are very often used, which rely on modeling techniques appropriate
to each time and space scale. The main methods used are ab-initio calculations, classical molecular dynamics (MD), kinetic Monte Carlo (KMC), mean field rate theory (MFRT), and dislocation
dynamics (DD). These methods are briefly presented along with some of their typical uses and main drawbacks. Some examples
are provided of the typical information obtained with each of the techniques. 相似文献
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Metallurgical and Materials Transactions A - Austenitic stainless steels such as 25Cr-35Ni-Nb, HP-Nb alloys are commonly used in high-temperature applications above 850 °C. The HP-Nb... 相似文献
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An in-depth discussion of pore formation is presented in this paper by first reinterpreting in situ observations reported in the literature as well as assumptions commonly made to model pore formation in aluminum castings. The physics of pore formation is reviewed through theoretical fracture pressure calculations based on classical nucleation theory for homogeneous and heterogeneous nucleation, with and without dissolved gas, i.e., hydrogen. Based on the fracture pressure for aluminum, critical pore size and the corresponding probability of vacancies clustering to form that size have been calculated using thermodynamic data reported in the literature. Calculations show that it is impossible for a pore to nucleate either homogeneously or heterogeneously in aluminum, even with dissolved hydrogen. The formation of pores in aluminum castings can only be explained by inflation of entrained surface oxide films (bifilms) under reduced pressure and/or with dissolved gas, which involves only growth, avoiding any nucleation problem. This mechanism is consistent with the reinterpretations of in situ observations as well as the assumptions made in the literature to model pore formation. 相似文献