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arXiv 2103.12290cond-mat.mtrl-sci
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熔池凝固条件时空变化下微观组织演化的多尺度模拟研究

Microstructure evolution under the space-time variational solidification conditions in a melt pool: A multi-scale simulation study

Fengyi Yu, Yanhong Wei, Qiaodan Hu, Jianguo Li

摘要:

熔池中凝固条件是时空变化的,熔池中的微观组织演变决定了焊接件的性能。为了反映熔池内凝固条件的变化,本文将微观相场方程与宏观热过程相结合,进行了多尺度模拟。首先,采用GR模型和TF模型对熔池局部区域的单晶凝固过程进行了数值模拟。结果表明,TF模型比GR模型更能反映变化情况。其次,通过TF模型对整个熔池区域进行了单晶凝固和多晶凝固模拟。结果表明,整个熔池的凝固条件的时空变异性。同时,变化条件对微观结构的演化有显著影响,包括外延生长阶段初始不稳定性的发生和竞争生长阶段收敛晶界和发散晶界的方向性演化。此外,观察到轴向晶粒结构的形成,这可以被认为是沿轴向和径向的晶粒之间的竞争。本文的研究表明了考虑池内变化条件的必要性。同时,PF模型能够准确地模拟变条件下的微观组织演化,在研究熔池凝固动力学方面具有很大的潜力。

英文摘要:

The properties of welded components are dominated by the microstructure evolution in the pool, where the solidification conditions are space-time variational. To represent the variational solidification conditions in the pool, the multi-scale simulation is carried out in this paper, combining the microscopic Phase-Field (PF) equations with the macroscopic thermal processes. Firstly, two different models, the GR model and TF model, are employed to simulate the single crystal solidification at a local region of the pool. Results suggest the TF model is more suitable to reflect the variational conditions than the GR model. Secondly, the single-crystal solidification and poly-crystal solidification at the whole region of the pool are performed through the TF model. The results demonstrate the space-time variabilities of the solidification conditions across the melt pool. Meanwhile, the variational conditions affect the microstructure evolution significantly, including the onset of initial instability at the epitaxial growth stage and the directional evolutions of the converging grain boundaries (GBs) and diverging GBs at the competitive growth stage. Moreover, the formation of axial grain structures is observed, which can be regarded as the competition between the grains along the axial direction and radial direction. This study indicates the necessity of considering the variational conditions in a pool. Meanwhile, the PF model can simulate microstructure evolution under the variational conditions accurately, which has a great potential for investigating solidification dynamics in the melt pool.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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