Abstract The present study reports development and application of a three dimensional phase field (PF) model, to investigate the microstructure evolution mechanism responsible for generation of spheroidal primary Al grains, associated with cooling slope processed semi solid slurry of A356 aluminium alloy. The cooling slope rheoprocessing technique involves solidification of flowing melt on an inclined slope surface, where gravity assisted fluid flow and shearing action between the flowing melt and the slope surface causes formation of near spherical primary solid fragments, and subsequent isothermal globularisation of the evolving primary solid. The present PF model implements a seed density based nucleation model. The seed density requirements to simulate microstructure evolution for different simulation/melt treatment conditions of cooling slope processing have been estimated based on initial experimentation. The simulated micrograph of slope exit state i.e, at the end of cooling slope processing has been used to estimate the number density and average size of constituent α-Al grains of the generated slurry, at slope exit state. The values obtained are fed subsequently as input parameters to simulate post slurry generation isothermal globularisation process. The model predictions are validated experimentally, thus establishing its capability to predict the characteristics of semisolid slurry at different stages of cooling slope rheoprocessing, in terms of solid content (volume fraction), diameter, density, and shape factor (sphericity) of nucleated primary Al grains.

中文翻译：

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Al-7Si-0.3镁合金半固态加工过程中球状晶粒形成的三维相场模拟

摘要 本研究报告了三维相场 (PF) 模型的开发和应用，以研究与冷却坡处理的 A356 铝合金半固态浆料相关的球状初生 Al 晶粒的微观结构演化机制。冷却斜坡流变处理技术涉及在倾斜的斜坡表面上流动熔体的凝固，其中重力辅助的流体流动和流动的熔体与斜坡表面之间的剪切作用导致近球形原生固体碎片的形成，以及随后演化出的原生固体的等温球化. 本 PF 模型实现了基于种子密度的成核模型。在初始实验的基础上，估计了冷却斜坡处理的不同模拟/熔体处理条件下模拟微观结构演变的种子密度要求。斜坡出口状态的模拟显微照片，即在冷却斜坡处理结束时，已用于估计在斜坡出口状态下生成的浆料的组成α-Al 晶粒的数量密度和平均尺寸。获得的值随后作为输入参数进料以模拟浆液生成后等温球化过程。模型预测得到了实验验证，从而确立了其预测冷却斜坡流变处理不同阶段半固体浆料特性的能力，包括固体含量（体积分数）、直径、密度、