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首页> 外文期刊>International Journal of Heat and Mass Transfer >Effect of thermal anisotropy on binary alloy dendrite growth
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Effect of thermal anisotropy on binary alloy dendrite growth

机译：热各向异性对二元合金枝晶生长的影响

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摘要

A numerical model to study the effect of thermal anisotropy on binary alloy dendrite growth is presented. The model is based on the volume averaged enthalpy method with explicit surface tension anisotropy for crystal orientation. Thermal anisotropy is incorporated using anisotropic thermal conductivity in the energy equation. This is done by splitting the anisotropic conductivity into two parts, equivalent isotropic conductivity and anisotropic departure source term, enabling the use of a conventional isotropic solver to model anisotropic heat transfer. The proposed model is applied to study the effect of thermal anisotropy ratio on tip velocity, aspect ratio and equivalent radius of an equiaxed grain growing in an undercooled binary alloy melt. It is found that the thermal energy stored in the grain during solidification plays an important role in interface evolution, and thus anisotropic conductivity in the solid affects the grain morphology. There is a consistent increase in the aspect ratio of grains with increase in thermal anisotropy ratio, although the grain volume remains almost invariant. Due to unequal growth rates of the perpendicular arms, severe distortion of the solid crystal is seen at higher thermal anisotropy ratios. The model is further extended to study the growth of multiple dendrites in order to simulate microstructure evolution with thermal anisotropy. It is observed that thermal anisotropy significantly affects the grain morphology at low grain density but has a smaller influence at high grain density as compared to other governing factors such as solute transport.
机译：提出了一个数值模型来研究热各向异性对二元合金枝晶生长的影响。该模型基于体积平均焓法，具有明确的表面张力各向异性，可用于晶体取向。在能量方程中使用各向异性导热系数将热各向异性纳入其中。通过将各向异性电导率分成等效的各向同性电导率和各向异性偏离源项两部分，可以使用常规的各向同性求解器对各向异性传热进行建模。该模型用于研究热各向异性比对过冷二元合金熔体中等轴晶粒长大速度，长宽比和当量半径的影响。发现在凝固过程中储存在晶粒中的热能在界面演化中起着重要作用，因此固体中的各向异性电导率会影响晶粒的形态。尽管晶粒体积几乎保持不变，但是随着热各向异性比率的增加，晶粒的长宽比会持续增加。由于垂直臂的生长速率不相等，因此在较高的热各向异性比下会看到固态晶体的严重变形。该模型进一步扩展为研究多个树枝状晶体的生长，以模拟具有热各向异性的微观结构演变。可以看出，与其他控制因素（如溶质迁移）相比，热各向异性在低晶粒密度下会显着影响晶粒形态，但在高晶粒密度下影响较小。

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