Abstract
A C15 Laves phase Ir2Y that forms in the Ir-Y binary system develops off-stoichiometry toward the Ir-rich composition at high temperatures, and its range of homogeneity becomes narrow with decreasing temperatures. One consequence of this solubility behavior is the formation of Ir3Y precipitates within the Ir2Y matrix of an Ir-30 mol%Y alloy. The orientation relationship between Ir3Y and Ir2Y has been identified as: (0001)Ir3Y||(111)Ir2Y and [2\\bar1\\bar10]Ir3Y||[\\bar110]Ir2Y. The similarity in the crystal structures of the two phases yields a plate-like Ir3Y precipitate showing a typical Widmanstätten structure. The growth of the precipitates has been suggested to follow the ledge mechanism. The interfacial character between the two phases has been identified in this study.
