Two-phase modeling directed toward hot tearing formation in aluminum direct chill casting
Two-phase modeling directed toward hot tearing formation in aluminum direct chill casting
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DOI：
10.1007/s11661-002-0040-6
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发表时间：
2002-07
期刊：
影响因子：
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通讯作者：
M. M’hamdi;A. Mo;C. L. Martin
中科院分区：
文献类型：
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作者：
M. M’hamdi;A. Mo;C. L. Martin
针对铝合金直冷铸造过程，建立了控制收缩驱动的熔体流动和热致变形的两相质量和动量守恒方程。因此，在同一个数学模型中同时解决了与凝固和随后的冷却过程中的热裂形成相关的两个主要机制。该方法统一了Farup和Mo概述的两相糊状区模型，Martinet等人概述的将糊状区视为液体饱和的粘塑性多孔介质的本构关系，和“经典”力学方法的热致变形固体（单相）材料使用线性运动学近似。一个温度场和一个独特的凝固路径被认为是输入到模型。的控制方程求解的一维（1-D）的情况下，有一些相关的DC铸造工艺。考虑到从液相到固相的动量转移的重要性，然后通过建模的例子证明。此外，模拟结果表明，控制糊状区固体骨架粘塑性行为的本构关系应考虑固体骨架可压缩/膨胀以及应力空间各向异性。计算出的液体压力和固体应力的峰值变成相关的热裂敏感性在铸造试验中测得的意义上说，具有最大的裂纹的试验是那些最高的压力和应力计算。
The two-phase mass and momentum conservation equations governing shrinkage-driven melt flow and thermally induced deformation are formulated for the aluminum direct chill (DC) casting process. Two main mechanisms associated with hot tearing formation during solidification and subsequent cooling are thus addressed simultaneously in the same mathematical model. The approach unifies the two-phase mushy zone model outlined by Farup and Mo, the constitutive relations that treat the mushy zone as a viscoplastic porous medium saturated with liquid outlined by Martinet al., and the “classical” mechanics approach to thermally induced deformations in solid (one-phase) materials using the linear kinematics approximation. A temperature field and a unique solidification path are considered as input to the model. The governing equations are solved for a one-dimensional (1-D) situation with some relevance to the DC casting process. The importance of taking into account the transfer of momentum from the liquid phase to the solid phase is then demonstrated through modeling examples. Furthermore, the modeling results indicate that the constitutive law governing the viscoplastic behavior of the solid skeleton of the mushy zone should take into account that the solid skeleton can be compressed/dilated as well as stress space anisotropy. Calculated peak values for liquid pressure and solid stress turn out to correlate to the hot tearing susceptibility measured in casting trials in the sense that trials having the largest cracks are those for which the highest pressures and stresses are computed.