After casting and solidification, Al-cast cylinder heads undergo a sequence of heat treatments to achieve the required strength. The phases responsible for the strengthening appear after solution heat treatment, quenching and artificial ageing. Although the state-of-the-art describes the occurrence of phases in this alloy for some treatment conditions, we missed modelled solutions to predict phases and their characteristics after any heat treatment. This work focuses on developing and validating a complete modelling routine to obtain the precipitates along any heat treatment history of an AlSi7Cu0.5Mg alloy. Firstly, we simulated the solidification process of the casting using the Scheil-approach. Secondly, we calculated the phases formed during cooling, solution heat treatment and ageing using the classical nucleation theory with the MatCalc© software based on the CALPHAD method. Finally, we validated the model with heat flow obtained by calorimetry and microstructures obtained by electron microscopy. After validation, the model can simulate the strengthening phases and explain the hardness ageing curves. On the other hand, the model to date could not reproduce the occurrence of the TiAlSi phase formed at low temperatures. This Ti-rich phase serves as nucleation sites for a fraction of the Q′ phases and decreases the β phases' precipitation kinetics.

中文翻译：

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热处理路径对 AlSi7Cu0.5Mg 合金中析出序列的影响

铸造和凝固后，铝铸气缸盖经过一系列热处理以达到所需的强度。负责强化的相出现在固溶热处理、淬火和人工时效之后。尽管最先进的技术描述了这种合金在某些处理条件下相的出现，但我们错过了预测任何热处理后相及其特性的建模解决方案。这项工作的重点是开发和验证完整的建模程序，以获得 AlSi7Cu0.5Mg 合金任何热处理过程中的沉淀物。首先，我们使用 Scheil 方法模拟了铸件的凝固过程。其次，我们基于CALPHAD方法，使用MatCalc©软件，利用经典成核理论计算了冷却、固溶热处理和时效过程中形成的相。最后，我们用量热法获得的热流和电子显微镜获得的微观结构验证了模型。经过验证，该模型可以模拟强化阶段并解释硬度时效曲线。另一方面，迄今为止的模型无法重现低温下形成的 TiAlSi 相的出现。这种富钛相充当一部分 Q' 相的成核位点，并降低了 β 相的沉淀动力学。