Abstract

Low-pressure die-cast (LPDC) 319 Al alloy is commonly processed with hot isostatic pressing (HIP), heat treatment, and chemical eutectic silicon modification for advanced automotive applications. Yet, the microstructure can be similarly influenced by each of these processes, which may obscure their isolated benefits. Hence, this study aimed to differentiate their effects by processing step blocks of LPDC 319 alloy with either a HIP or ambient-pressure heat treatment, each for 2 h at 500 °C, or with strontium additions up to 150 ppm. Both chemical and thermal modifications of eutectic silicon were found to effectively improve alloy conductivity. However, the potential benefits of strontium to alloy strength and hardness were offset by the decreases in density associated with the addition. In contrast, the as-cast, unmodified samples featured relatively high densities, although this limited the ability of the HIP treatment to reduce porosity. With identical temperatures and heating times, both the HIP and heat treatment promoted comparable Al₂Cu dissolution and silicon spheroidization. Accordingly, both treatments generally improved hardness and strength, and increased thermal and electrical conductivities by up to 12.5%. Thus, these processing parameters can each contribute to the development of enhanced engineering components individually, thereby reducing the need for their combined application.

中文翻译：

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通过热等静压，热处理或化学处理制备的低压模铸319铝的机械性能和电导率

摘要

低压压铸（LPDC）319铝合金通常通过热等静压（HIP），热处理和化学共晶硅改性处理，以用于高级汽车应用。然而，这些过程中的每一个都可能类似地影响微结构，这可能会掩盖其孤立的优势。因此，本研究旨在通过采用HIP或常压热处理（分别在500°C下进行2小时）或添加高达150 ppm的锶处理LPDC 319合金的台阶来区别其作用。共晶硅的化学改性和热改性均可有效提高合金的导电性。但是，锶对合金强度和硬度的潜在好处被与添加有关的密度降低所抵消。相比之下，未改性的样品具有相对较高的密度，尽管这限制了HIP处理降低孔隙率的能力。在相同的温度和加热时间的情况下，HIP和热处理均可以促进可比的Al₂ Cu溶解和硅球化。因此，两种处理通常都提高了硬度和强度，并使导热率和电导率提高了高达12.5％。因此，这些处理参数每个都可以分别有助于增强型工程组件的开发，从而减少了对其组合应用程序的需求。