铸造耐热 Al-Si-Cu-Ni-Mg 合金是制备高功率密度发动机活塞等耐热轻量化部件的重要基础材料，通过添加高熔点、低热扩散系数的 Sc 元素来调控合金的相结构和形貌是提升此类合金耐温性的重要思路。 因此，探究了 Sc 元素添加及其含量对铸造耐热 Al-Si-Cu-Ni-Mg 活塞合金凝固组织和热暴露过程中富铜镍相组织演变的影响。 结果表明，

随 Sc 含量增加，活塞合金中形成 AlSiCuNiSc 新相，并且 AlSiCuNiSc 相的数量和尺寸随 Sc 含量的增加而增加；此外，随着 AlSiCuNiSc 相的形成，δ-Al3CuNi 相发生由典型共晶层片向棒杆状组织的转变。 热暴露过程中，δ-Al3CuNi 相中的Cu 和 Ni 原子向 α-Al 基体中扩散，并在 δ-Al3CuNi 的相界面处形成纳米尺度的 γ-Al7Cu4Ni 相；而富 Sc 的 AlSiCuNiSc相在热暴露前后形貌和成分几乎不发生变化，表现出极高的热稳定性；分析认为，高熔点、低热扩散系数的 Si 和 Sc 等原子在富铜镍相中的存在极大提高了富铜镍相的热稳定性。

Cast heat-resistant Al-Si-Cu-Ni-Mg alloys serve as crucial foundational materials for fabricating heat-resistant, lightweight components, such as pistons, which are used in high-power-density engines. A key strategy to increase the temperature resistance of these alloys involves incorporating Sc elements that possess high melting points and low thermal diffusion coefficients to regulate the phase structure and morphology of the alloys. Therefore, the effects of the addition and content of Sc on the microstructure and evolution of the AlCuNi phase of heat-resistant Al-Si-Cu-Ni-Mg piston alloys were investigated. The results reveals that with increasing Sc content, a new AlSiCuNiSc phase forms in the piston alloy, and the number and size of the AlSiCuNiSc phases increases with increasing Sc content. In addition, with the formation of the

AlSiCuNiSc phase, the δ-Al3CuNi phase undergoes a transformation from a typical eutectic lamellar to a rod-like structure. During thermal exposure, the Cu and Ni atoms in the δ-Al3CuNi phase diffuse into the α-Al matrix, and a nanoscale γ-Al7Cu4Ni phase is formed at the phase interface of δ-Al3CuNi. However, the morphology and composition of the AlSiCuNiSc phase almost did not change before and after heat exposure, indicating extremely high thermal stability. The presence of atoms such as Si and Sc with high melting points and low thermal diffusivity in the AlSiCuNiSc phase greatly improves its thermal stability.