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

Abstract

Ternary eutectics provide a unique opportunity for studying the eects 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 solidied in a constant temperature gradient of 3 K/mm at velocities between 0.2 and 5.0 m/sec. Under these conditions, the two intermetallic phases appear to grow as closely coupled rods in an (Al) matrix, with the solidication velocity aecting the specic 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 specic orientation relationships. Although no conclusive connection to morphology has yet been found, two dierent sets of orientation relationships between the three phases have thus far been identied.