Abstract Rheological transitions from suspension flow to granular deformation and shear cracking are investigated in equiaxed-globular semi-solid alloys by combining synchrotron radiography experiments with coupled lattice Boltzmann method, discrete element method (LBM-DEM) simulations. The experiments enabled a deformation mechanism map to be plotted as a function of solid fraction and shear rate, including a rate dependence for the transition from net-contraction to net-dilation, and for the initiation of shear cracking. The LBM-DEM simulations are in quantitative agreement with the experiments, both in terms of the strain fields in individual experiments and the deformation mechanism map from all experiments. The simulations are used to explore the factors affecting the shear rate dependence of the volumetric strain and transitions. The simulations further show that shear cracking is caused by a local liquid pressure drop due to unfed dilatancy, and the cracking location and its solid fraction and shear rate dependence were reproduced in the simulations using a criterion that cracking occurs when the local liquid pressure drops below a critical value.

中文翻译：

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半固态合金的流变转变：原位成像和 LBM-DEM 模拟

摘要 结合同步辐射成像实验与耦合晶格玻尔兹曼法、离散元法 (LBM-DEM) 模拟，研究了等轴球状半固态合金从悬浮流动到颗粒变形和剪切开裂的流变转变。实验能够绘制变形机制图作为固体分数和剪切速率的函数，包括从净收缩到净膨胀的转变以及剪切​​开裂开始的速率依赖性。LBM-DEM 模拟与实验在定量上一致，无论是在单个实验中的应变场还是所有实验的变形机制图方面。模拟用于探索影响体积应变和转变的剪切速率依赖性的因素。