Modelling and validation: Casting of Al and TiAl alloys in gravity and centrifugal casting processes
Modelling and validation: Casting of Al and TiAl alloys in gravity and centrifugal casting processes
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DOI：
10.1016/j.apm.2013.03.030
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发表时间：
2013-08
影响因子：
5
通讯作者：
N. J. Humphreys;D. Mcbride;D. Shevchenko;T. N. Croft;P. Withey;N. Green;M. Cross
中科院分区：
文献类型：
--
作者：
N. J. Humphreys;D. Mcbride;D. Shevchenko;T. N. Croft;P. Withey;N. Green;M. Cross
最能充分利用高温钛合金性能的部件的特点是具有几毫米厚和数百毫米长的薄截面。然而，这些合金很难加工，在熔融状态下具有很高的反应性，因此在加工过程中需要较低的过热度。因此，离心铸造被用作一种候选生产方法，因为在离心力的作用下，金属在凝固之前可以快速填充远小于一毫米的厚度。然而，由于液态金属速度较高，因此存在湍流和液态金属内存在任何气体的截留的高风险。这一具有挑战性的应用涉及复杂的旋转几何形状、显着的离心力和高速瞬态自由表面流，以及同时进行的传热和凝固。捕获这些相互作用的物理现象、自由表面流、滞留空气和相关缺陷是一项复杂的建模任务。基于作者先前描述的捕获和验证旋转系统的流体动力学行为的计算建模的早期工作，本贡献考虑了此类系统的建模和验证，以捕获耦合流动和热凝固行为以及相关的缺陷发展。采用基准测试用例来验证凝固对铝合金流动性的影响。还针对一系列铸造实验进行了验证，以建立模型捕获填充过程并预测由于凝固金属内滞留空气而导致的缺陷的模型。
Components which best utilise the properties of high temperature titanium alloys are characterised by thin sections of a few millimetres thickness and hundreds of millimetres length. These alloys however are difficult to work with, being highly reactive in a molten state, necessitating a low superheat during processing. Centrifugal casting is therefore utilised as a candidate production method, as under the centrifugal force, metal can rapidly fill thicknesses substantially less than a millimetre before it solidifies. However, due to the high liquid metal velocity developed there is a high risk of turbulent flow and of the trapping of any gas present within the liquid metal.This challenging application involves a combination of complex rotating geometries, significant centrifugal forces and high velocity transient free surface flows, coupled with simultaneous heat transfer and solidification. Capturing these interacting physical phenomena, free surface flows, trapped air and associated defects is a complex modelling task.Building upon earlier work on computational modelling the authors have previously described to capture and validate the fluid dynamics behaviour of rotating systems, this contribution considers the modelling and validation of such systems to capture the coupled flow and thermal solidification behaviour and associated defect development.A bench-mark test case is employed to validate the effect of solidification on the fluidity of an aluminium alloy. Validation is also performed against a series of casting experiments to establish the models ability to capture the filling process and predict defects due to air entrapment within the solidified metal.