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随着电子通讯等行业的快速发展，对高导热铸造铝合金材料性能要求日益增加。本文以在电子通讯等行业广泛使用的Al-7Si（ wt%，下同）铸造铝合金为对象，系统分析了热处理工艺制度以及少量的Mg元素添加对Al-7Si系合金微观组织及性能的影响。结果表明：固溶后在300℃下进行保温热处理有利于共晶Si的球化，并减小溶质原子在铝基体中的固溶度，从而导致Al-7Si合金导热性能的提升及硬度的降低；在Al-7Si合金中添加微量Mg（ 0.4%）后进行三级热处理（固溶处理+300℃热处理+180℃热处理）不仅有助于共晶Si的球化，而且能促使纳米尺度（ Mg,Si）强化相的析出以及基体中固溶的Mg、Si元素含量的降低，从而同时提高合金的力学性能和导热性能。经历三级热处理的Al-7Si-0.4Mg合金热导率和显微硬度可达189 W/(m·K)和73.5 HV，相较于铸态Al-Si合金分别提升了11.2%和62.6%。Al-Si alloys have been widely used in automotive, aerospace, electronics and communication industries due to their excellent castability, low thermal expansion, and good wear and corrosion resistance. However, the presence of coarse eutectic Si often results in relatively low thermal conductivity. With the rapid development of the electronics and communication industries, the demand for thermal conductivity and mechanical properties of materials is increasing. In this study, the effects of heat treatment and minor Mg addition on the microstructure, mechanical properties, and thermal conductivity of Al-7Si alloys were systematically investigated.
The results indicate that heat treatment at 300℃ after solution treatment promotes the spheroidization of eutectic Si and reduces the solid solubility of solute atoms in the aluminum matrix, thereby enhancing the thermal conductivity and reducing the hardness of the Al-7Si alloy. The three-step heat treatment process (solution treatment + 300℃ treatment + 180℃ treatment) not only facilitates the spheroidization of eutectic Si, but also induces the precipitation of nanoscale (Mg, Si) strengthening phases and further decreases the solid solubility of solute elements in the Al-7Si alloy with 0.4%Mg addition. After the three-step heat treatment, the thermal conductivity and microhardness of the Al-7Si-0.4Mg alloy reach to 189 W/(m·K) and 73.5 HV, respectively. Compared to the as-cast Al-7Si alloy, they are increased by 11.2% and 62.6% respectively.
According to the Wiedemann-Franz law and the Matthiessen-Fleming rule, the primary factors influencing the thermal conductivity of alloys are solute atoms in solid solution and secondary phases. In this study, a three-step heat treatment process was used to transform the plate-like eutectic silicon in the Al-7Si-0.4Mg alloy into fine spherical particles. Additionally, micrometer-sized silicon particles and nanoscale (Mg, Si) precipitates were induced within the alloy matrix. This microstructural modification simultaneously enhanced both the thermal conductivity and mechanical properties of the alloy. Our work is expected to inspire the design of Al-Si alloy with high strength and high conductivity.-
Keywords:
- Al-Si alloy /
- Microstructure /
- Thermal conductivity /
- Mechanical property
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