Crystal orientation and morphology in Al-Ag-Cu ternary eutectic

Ternary eutectics provide a unique opportunity for studying the effects of complex microstructure formation, as three distinct phases must be formed simultaneously from the melt. In order to produce fully coupled three-phase growth, Al-Ag-Cu at the ternary eutectic composition was directionally solidified in a constant temperature gradient of 3 K/mm at velocities between 0.2 and 5.0 μm/sec. Under these conditions, the two intermetallic phases appear to grow as closely coupled rods in an α(Al) matrix, with the solidification velocity affecting the specific morphologies chosen by the rods and the general degree of alignment of the structure. Crystal orientations were examined by EBSD to determine if variations in morphology within a single sample are due to specific orientation relationships. Although no conclusive connection to morphology has yet been found, two different sets of orientation relationships between the three phases have thus far been identified.