铝合金因其轻质、优异的力学性能以及良好的导电和导热性能等特点，已成为交通运输、电子通讯以及航空航天等领域的重要材料。随着汽车和通讯领域的高速发展，铝合金制造的零部件，如汽车发动机的缸体和缸盖、电机外壳以及5G基站散热器等，对材料的导热性能提出了更高的要求。然而，目前常用的铸造铝合金尽管具有较高的强度，可达约300 MPa，但其导热系数仅在90至120 W/m K之间，无法满足其应用领域日益增长的散热需求。因此，对铝合金的导热性能进行系统研究，并设计研发具有更高导热性能的铝合金，已成为工程应用中的迫切需求。铝合金的导热性能主要受合金元素和第二相等因素的影响。本文针对这些影响因素，建立了合金元素和第二相与铝合金导热系数的理论模型，并开展了它们对铝合金导热性能影响规律的理论研究。然后，基于理论模型设计并研发了一种综合性能优异的高导热铝合金，为高导热铝合金的工程应用提供了理论及实验基础。基于金属导热理论，建立了铝合金的导热系数与合金元素的理论模型。在铝合金中，各种合金元素的添加对导热性能的削弱程度不同。合金元素在固溶态下对导热性能的削弱顺序为：Cr > V > Mn > Ti > Zr > Si > Mg > Cu > Zn。而且，合金元素在固溶态下对导热性能的削弱强度远高于其在析出态下的影响。此外，当Si与Mg或Cu元素共存时，它们对彼此固溶度的影响以及结合形成金属间化合物都会对导热性能产生显著影响。针对Al-Si合金中共晶Si相的形貌可变的特征，建立了具有片状和纤维状共晶Si相的共晶组织的理论模型。基于理论模型，提出并证实了Al/Si界面热阻对Al-Si合金导热性能的重要性。当共晶Si相呈纤维状或球状时，Al-Si合金的导热性能高于呈片状时的情况。其中，片状共晶Si相的纤维化有助于降低传热载流子受到Al/Si界面和共晶Si相的散射概率，从而提高传热效率和改善合金的导热性能。基于理论研究结果，选择了低固溶度的Ni和Fe元素，并设计其组织主要包含纤维状相和小尺寸的片状相，实现了在保持高导热性能的同时显著提高强度的目标，成功制备了一种新型的高导热Al-Ni-Fe合金。其中，Al-3Ni-0.6Fe合金的导热系数、抗拉强度、屈服强度和伸长率分别达到189 W/m K、168 MPa、69 MPa和19%。同时，基于Al-Ni基合金的高温稳定性，Al-Ni-Fe合金有望在散热和耐热领域替代传统的Al-Si基合金，具有重要的工程应用潜力。
Aluminum alloys have become essential materials in fields such as transportation, communication, and aerospace due to their lightweight, excellent mechanical properties, as well as good electrical and thermal conductivity. With the rapid development of the automotive and communication industries, components made of aluminum alloys, such as engine blocks and cylinder heads for automobiles, motor housings, and 5G base station radiators, have placed higher demands on thermal conductivity of materials. However, although commonly used cast aluminum alloys exhibit high strength, reaching approximately 300 MPa, their thermal conductivity is only between 90 and 120 W/m K, which cannot meet the increasing demand for heat dissipation applications. Therefore, there is an urgent requirement in engineering applications to systematically study the thermal conductivity of aluminum alloys and to design and develop aluminum alloys with higher thermal conductivity.The thermal conductivity of aluminum alloys is mainly influenced by factors such as alloying elements and second phases. This paper establishes theoretical models for the impact of alloying elements and the second phase on the thermal conductivity of aluminum alloys and conducts theoretical research on their effects. Subsequently, based on the theoretical models, a high thermal conductivity aluminum alloy with excellent comprehensive performance is designed and developed, providing both theoretical and experimental foundations for engineering applications of high thermal conductivity aluminum alloys.Based on the theory of metal thermal conduction, a theoretical model for the relationship between alloying elements and the thermal conductivity of aluminum alloys is established. Different alloying elements weaken the thermal conductivity of aluminum to various degrees. The weakening order of alloying elements in solid solution on the thermal conductivity of aluminum is Cr > V > Mn > Ti > Zr > Si > Mg > Cu > Zn. Besides， the effect of alloying elements in solid solution on the thermal conductivity of aluminum is much more significant than when in the precipitated state. In Al-Si-Mg and Al-Si-Cu alloy systems, the solid solubilities of Si, Mg, and Cu affect each other, and the synergistic effect of Si, Mg, and Cu have a significant impact on thermal conductivity.Based on the Effective Unit Cell Model, a theoretical model for the eutectic structure of Al-Si alloys with lamellar and fibrous eutectic Si is established to address the variable eutectic Si morphology. Based on the theoretical model, the significance of the Al/Si interfacial thermal resistance on the thermal conductivity of Al-Si alloys is proposed and confirmed. When the eutectic Si is fibrous or globular, the thermal conductivity of Al-Si alloys is higher than that when it is lamellar. Specifically, the transformation of eutectic Si from lamellar to fibrous helps reduce the scattering probability of heat carriers at the Al/Si interface and eutectic Si, thereby enhancing heat transfer efficiency and improving the thermal conductivity of Al-Si alloys. Based on theoretical research results, Ni and Fe elements are selected, and the microstructure is designed to comprise fibrous and small-sized lamellar phases. The design aims to significantly enhance strength while maintaining high thermal conductivity. A novel high thermal conductivity Al-Ni-Fe alloys is successfully prepared. For instance, the thermal conductivity, tensile strength, yield strength and elongation of Al-3Ni-0.6Fe alloys are approximately 189 W/m K, 168 MPa, 69 MPa and 19%, respectively. Furthermore, considering the high-temperature stability of Al-Ni based alloys, Al-Ni-Fe alloys are expected to replace traditional Al-Si based alloys in heat dissipation and heat resistance applications, offering significant engineering potential.
