Oxygen induced chemical ordering and ultrafine lamellar structure formation in a Ti-48 at. % Al alloy

Abstract

ABSTRACTInfluence of oxygen on the microstructure development of a Ti-48 at. % Al alloy has been investigated by means of transmission electron microscopy and 1D atom probe. Oxygen is found to significantly increase the temperature of the α → α2 chemical ordering reaction. As a consequence, above a critical oxygen content, the α → α2 transformation is substituted to the α → γm massive transformation when the Ti-48 Al alloy is quenched from the single a-phase field. In such a case, our pervious work has shown that the alloy exhibits a fully (α2 + γ) ultrafine lamellar structure. The present work gives a complete description of the ultrafine lamellar structure formation which, in opposition to the classical lamellar structure formation, involves an intragranular nucleation and growth of the γ phase within the α2 matrix.