ABSTRACT Unsteady-state upward solidification experiment was carried out with the Al-3Cu-3Ni (wt.%) alloy. Temperature profiles were obtained through a water-cooled directional solidification device. Analysis on the resulting as-cast microstructure and its adaptation to thermal solidification parameter, such as growth and cooling rates and solidification local time, VL, TR and tSL, respectively, was carried out. The results showed that the resulting microstructure is constituted by an Al-rich primary phase (Al α ), characterised by a dendritic network, and by second phases that take place within the interdendritic regions, forming a eutectic mixture composed by the β-Al3Ni + θ-Al2Cu intermetallic compounds (IMCs), whose size and morphology have been affected by VL and TR. The length of the microstructural scale of the Al α phase was measured by the secondary dendritic spacing (λ 2). The experimental mathematical expression of λ 2 obtained in this work was compared with mathematical models proposed in the literature that associate tSL-λ 2 for non-equilibrium and equilibrium solidification conditions.

中文翻译：

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AlCuNi合金的凝固热参数、显微组织演变和枝晶生长

摘要 采用 Al-3Cu-3Ni (wt.%) 合金进行了非稳态向上凝固实验。通过水冷定向凝固装置获得温度曲线。分析了所得到的铸态微观结构及其对热凝固参数的适应性，例如生长和冷却速率以及凝固局部时间，分别是 VL、TR 和 tSL。结果表明，所得显微组织由富含 Al 的初生相 (Al α ) 构成，其特征在于枝晶网络，以及在枝晶间区域内发生的第二相，形成由 β-Al3Ni + 组成的共晶混合物。 θ-Al2Cu 金属间化合物 (IMC)，其尺寸和形态受 VL 和 TR 影响。Al α 相的显微组织尺度的长度通过二次枝晶间距(λ 2 )来测量。在这项工作中获得的 λ 2 的实验数学表达式与文献中提出的将 tSL-λ 2 关联为非平衡和平衡凝固条件的数学模型进行了比较。