Microstructure Analysis of The Channel Regions in Dual Two-phase Intermetallic Alloy Based on The Ni₃Al-Ni₃V Pseudo-binary Alloy System

<jats:title>ABSTRACT</jats:title><jats:p>Dual two-phase intermetallic alloys based on the Ni<jats:sub>3</jats:sub>Al-Ni<jats:sub>3</jats:sub>V pseudo-binary alloy system have been reported to display high phase and microstructure stabilities and good mechanical properties at high temperature and are therefore considered to be used as a next generation type of high temperature structural materials. The microstructure of the dual two-phase intermetallic alloys is composed of primary Ni<jats:sub>3</jats:sub>Al and the channel (eutectoid) regions consisting of Ni<jats:sub>3</jats:sub>Al+Ni<jats:sub>3</jats:sub>V. In this study, the microstructure of the channel regions was investigated by a transmission electron microscope (TEM). The contrasts of the channel regions showed a complicated microstructure in bright-field images. However, the electron beam diffraction consisted of a single set of patterns and the spots did not accompany streaks, indicating that crystallographic coherency among the constituent phases or the domains is very high. It was also shown that the lattice misfit between the a-axis of Ni<jats:sub>3</jats:sub>Al and the c-axis of Ni<jats:sub>3</jats:sub>V is larger than that between the a-axis of Ni<jats:sub>3</jats:sub>Al and the a-axis of Ni<jats:sub>3</jats:sub>V. From the dark-field observation, it was found that the c-axis of Ni<jats:sub>3</jats:sub>V domains in the channel regions is oriented perpendicular to the interface between primary Ni<jats:sub>3</jats:sub>Al and Ni<jats:sub>3</jats:sub>V. Therefore, it is suggested that the crystallographic orientation of Ni<jats:sub>3</jats:sub>V in the channel regions is aligned in the manner of lowering an internal stress caused by the lattice misfit between primary Ni<jats:sub>3</jats:sub>Al precipitates and Ni<jats:sub>3</jats:sub>V domains.</jats:p>