Solidification thermal parameters, microstructural evolution and dendritic growth in an AlCuNi alloy

Abstract

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.