Effect of directional solidification rate on microstructure and orientation of hypereutectic Al-Al2Cu alloy

The microstructure and orientation of directionally solidified Al-40%Cu hypereutectic alloy were investigated, and the different microstructures were formed because of the growth competition between eutectic phase and the primary Al2Cu phase. By X-ray diffraction techniques, the pole figures of Al2Cu phase were tested within the macro-orientations and the orientation distribution function (ODF) was calculated. Meanwhile the micro-orientations of directional solidification samples were determined by EBSD. At the directional solidification rate 2 μm/s, the microstructure is all eutectic (Al/Al2Cu) phase, in which Al2Cu phase has the orientation of (001) direction; however, at 10 μm/s the primary Al2Cu phase dendrite with faceted characteristic grows ahead of eutectic phase, which has mainly (001) orientation. When the solidification rate reaches 100 μm/s, Al2Cu phase with non-faceted characteristic grow into complex morphology, and its orientation focuses on the (100), (110) and (001) directions. Al2Cu phase grows along with the direction of heat flux. The results of XRD analysis show that dendritic morphology and orientation can be well controlled under directional solidification with relatively lower rate. © 2015, Science Press. All right reserved.