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首页> 外文期刊>Results in Physics >Numerical investigations of freckles in directionally solidified nickel-based superalloy casting with abrupt contraction in cross section
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Numerical investigations of freckles in directionally solidified nickel-based superalloy casting with abrupt contraction in cross section

机译：截面凝固收缩的定向凝固镍基高温合金铸件中雀斑的数值研究

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摘要

Evolution of grain structure and formation of freckle defects were simulated in directionally solidified nickel-based superalloy casting with abrupt contraction in cross-section area. A two-dimensional (2D) Cellular Automaton (CA) – Finite Element (FE) model was presented. The transport of liquid momentum, heat and solute mass at macroscopic scale, the development of grain envelopes at mesoscopic scale and microsegregation were fully coupled. Influences of alloying elements, cooling rate and geometrical shape of casting on freckle formation were studied. CAFE simulations show that through reducing the initial concentration of destabilizing element (W), the formation of freckle along casting edges was suppressed. Elements such as Co, Ti and Ta are not critical elements that affect density inversion in mushy region. Increasing cooling rate apparently decreased the freckling tendency. Without geometric contraction, there was no obvious formation of freckles along casting edges. It was numerically showed that the contraction in cross section introduced the high-permeability path for the upward fluid flow during directional solidification, which enhanced the freckling tendency.
机译：模拟了横截面突然收缩的定向凝固镍基高温合金铸件的晶粒结构演变和雀斑缺陷的形成。提出了二维（2D）细胞自动机（CA）-有限元（FE）模型。宏观尺度上的液体动量，热量和溶质的传输，介观尺度下的包膜的发展和微观偏析是完全耦合的。研究了合金元素，冷却速度和铸件几何形状对雀斑形成的影响。 CAFE模拟表明，通过降低去稳定元素（W）的初始浓度，可以抑制沿铸件边缘形成的雀斑。诸如Co，Ti和Ta之类的元素并不是影响糊状区域密度反演的关键元素。冷却速度的增加显然减少了雀斑的趋势。没有几何收缩，沿着铸造边缘就没有明显的雀斑形成。数值计算表明，截面收缩为定向凝固过程中的向上流动引入了高渗透率的路径，从而增强了雀斑的趋势。

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