Ternary eutectic growth and associated tensile properties of directionally solidified Al 87 Si 11 Ni 2 alloy

The directional growth mechanism and associated tensile properties of ternary Al 87 Si 11 Ni 2 eutectic alloy were investigated within a wide growth velocity range from 1 to 120 mu m s - 1 at a constant temperature gradient of 380 K cm -1 . If eutectic growth velocity was below 40 mu m s - 1 , this alloy exhibited a ternary lamellar eutectic structure composed of Si plates, Al 3 Ni chips and alpha Al matrix. As growth velocity increased to faster regime, the microstructure evolved into a complex structure characterized by primary alpha Al dendrites plus ternary eutectics. Correspondingly, the preferred crystalline orientation along solidification direction transformed from (101) alpha Al // (010) Al 3 Ni // (101) S i to (001) alpha Al // (010) Al 3 Ni //(113) S i . The tensile strength initially increased with the rise of growth velocity until 40 mu m s - 1 , primarily due to the refinement of eutectic structure, and then decreased beyond this threshold, mainly resulting from the coarsening of primary alpha Al phase.