Contribution to the analysis of the α/β interface in some titanium alloys

In (α + β) titanium alloys, the interface between the α and β phases has been widely studied, and many conflicting results have been published concerning the formation of an interface phase having an hcp or fcc crystalline structure. Several authors consider that this phase is an artifact and consists of a titanium hydride formed during thin foil preparation for TEM examination. This paper reports examinations by TEM and STEM of heat-treated Ti–6Al–4V alloy and two titanium molybdenum aluminides. The formation of an α/β interface phase is discussed as a function of composition heat-treatment and thin foil preparations. Particularly, for Ti–6Al–4V in a nonequilibrium state, a strong concentration gradient was revealed in the α/β interface, and a metastable interface phase enriched in beta-stabilizers with an fcc structure has been clearly characterized.