PHASE AND STRUCTURAL TRANSFORMATIONS IN Ti-Ta ALLOYS IN WIDE REGION OF COMPOSITIONS

摘要

Optical microscopy, X-ray diffraction, transmission electron microscopy, and hardness measurements were used to study the structure of quenched Ti-Ta alloys containing 1-40 at. percent tantalum. Two martensitic phases, alpha' and alpha", are formed in quenched Ti-Ta alloys. The type of mariensite crystal structure is determined by the composition of the alloy. The alpha'-phase is formed in the alloys containing up to 10 at. percent tantalum. The orthorhombic alpha"-phase was found in the alloys containing 15-30 at. percent Ta. The concentration dependence of the lattice parameters of the alpha"-phase is given. Omega-phase precipitation were not found in quenched alloys. The alloys of 35-40 at. percent Ta consist of metastable beta-phase only upon quenching. The electron diffractions patterns of the Ti-Ta alloys containing from 25 to 35 at. percent tantalum exhibit diffuse scattering. It was established that stress-induced {110}_beta and {332}_beta twinning appeared in metastable beta-phase.