Research on Microstructure Evolution of Al–Al2Cu Eutectic by Regional Melting under Directional Solidification

Abstract

AbstractAl–Al2Cu eutectic is prepared by regional melting through vacuum directional solidification furnace in an experiment. The effects of different pulling rates, heating power, and transition acceleration on the microstructure evolution of Al–Al2Cu eutectic under directional solidification are analyzed. Four constant growth rates of 3, 6, 9, and 15 mm min−1 are selected for the pulling rate. The primary Al2Cu phase will precede the coupled eutectic phase. The morphology of the irregular faceted primary Al2Cu phase is coarse and the feature of growth is transformed from faceted to non‐faceted as the pulling rate increases. The microstructure at three different heating powers is studied. With the increase of heating power, the primary Al2Cu phase in the alloy decreases, the eutectic structure increases, and the eutectic spacing of the alloy is obviously refined. The pulling rate is changed from 3 to 6 mm min−1, 6 to 9 mm min−1, and 9 to 15 mm min−1, respectively, in directional solidification for transition acceleration. The increase of the pulling rate will change the morphology of the primary Al2Cu phase and produce a partial rod eutectic structure. The lamellar eutectic spacing obtained by transition acceleration is smaller than that obtained by the same constant growth rate.