Solidification cracking is a longstanding and serious problem in metallurgical engineering that is encountered during casting, welding, and additive manufacturing. Extensive research has been conducted on the cracking susceptibility associated with solidification paths, microstructural effects, and thermal conditions, but it remains highly challenging to precisely predict and evaluate the solidification cracking, especially the solid bridging phenomenon and grain size dependence. In this study, a new theoretical model based on solid bridge fracture is proposed for modeling solidification cracking. The occurrence of cracking depends on competition between thermal stress accumulation and solid-bridge strength development, which is fundamentally distinct from existing models in which the cracking depends on liquid feeding. A crack-like structure is utilized to determine the thermal stress at a dendrite root, and demonstrates the absence of stress singularity in a solidifying crack. Grain features are incorporated to show that grain refinement effectively inhibits cracking by lowering the rate of accumulation of thermal stress. In this sense, the cracking susceptibility can be quantified based on grain size distributions. Numerical analyses of binary aluminum alloys validate the proposed model and provide a rational interpretation of reported experimental results in terms of cracking susceptibility, grain size effects, and cooling rate effects. This study presents and validates one of the first solid-bridge fracture-based solidification cracking models, and thus provides a new perspective to support investigation of solidification cracking.

中文翻译：

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凝固裂纹建模：实心桥断裂的新视角

凝固裂纹是冶金工程中铸造、焊接和增材制造过程中遇到的一个长期存在的严重问题。人们对与凝固路径、微观结构效应和热条件相关的裂纹敏感性进行了广泛的研究，但精确预测和评估凝固裂纹，特别是固体桥接现象和晶粒尺寸依赖性仍然具有很大的挑战性。在这项研究中，提出了一种基于实体桥断裂的新理论模型来模拟凝固裂纹。裂纹的发生依赖于热应力积累和固桥强度发展之间的竞争，这与现有模型中依靠液体供给产生裂纹有着本质的区别。利用类裂纹结构来确定枝晶根部的热应力，并证明凝固裂纹中不存在应力奇异性。结合晶粒特征表明，晶粒细化可通过降低热应力累积率来有效抑制裂纹。从这个意义上说，裂纹敏感性可以根据晶粒尺寸分布来量化。二元铝合金的数值分析验证了所提出的模型，并为报告的裂纹敏感性、晶粒尺寸效应和冷却速率效应方面的实验结果提供了合理的解释。这项研究提出并验证了第一个基于实体桥断裂的凝固裂纹模型，从而为支持凝固裂纹的研究提供了新的视角。