Microstructures of Ni3Al alloys as a function of Cr and Al levels

Abstract

Several alloys based on boron-doped Ni3Al are undergoing alloy development for a wide range of potential uses. The microstructures of several of these alloys were characterized by transmission electron microscopy as a function of the chromium and aluminum levels. The series included alloys with 0 to 10 at. % Cr and with 15.6 to 21% Al, see Table I.In Ni-AI alloys with low aluminum content and in most Ni-Al alloys with chromium additions, a twophase γ’ plus γ structure resulted. The major phase (and matrix) was ordered γ’ and the minor phase disordered γ· Both phases appeared interconnected and were completely epitactic. The ordered phase was aluminum-enriched while the disordered phase was chromium-enriched. Within the disordered phase a reprecipitation of γ’ often occurred, depending on heat treatment, and gave an appearance of a “disordered web”. Typical x-ray energy dispersive spectroscopic (EDS) analyses are listed in Table II.