ESBD Analysis of the Structure of Cast and Quenched Hafnium–Titanium Alloys

详细

This paper presents the results of investigation of alloys Hf–45% Ti and Hf–70% Ti structures which were formed under different kinetic conditions of the β → α (bcc → hcp) polymorphic transformation occurence. We used methods of metallography and EBSD analysis during our investigation. We have shown that the Hf–Ti alloys in the cast state exhibit a mixed structure consisting of α-phase crystals of several morphological types: large plates, groups of small parallel plates, and fine crystallites of the shape close to polyhedral. The α-phase structure of the Hf–Ti alloys after quenching consists of martensite crystals grouped into packets. In each packet, there are several crystallographic orientations of 12 possible orientations corresponding to Burgers orientation relationships, and no regular alternation of different orientations of the α phase were revealed in the packet. Irrespective of the cooling rate of the Hf–Ti alloys upon the β → α polymorphic transformation, within the initial β-phase grain, the same set of orientations of the α phase occurs. In the studied Hf–Ti alloys, the misorientation of substructure elements within the α-phase crystal reaches ~5.0° for the as-cast state and ~2.2° after quenching.