Microstructural evolution in wire-drawn Ti-22Al-26Nb powder

Abstract

The microstructural evolution in Ti-22Al-26Nb, as it was drawn from hot isostatically pressed powder to a 0.13 mm wire, is followed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The primary α2 particles present in the starting powder persist throughout the drawing process, although they undergo both morphological and crystallographic changes. They are altered from 4 to 5-µm-diameter, equiaxed particles to 1 to 2-µm-diameter, highly elongated particles by the drawing process. In addition, these primary particles transform in situ to α2 + O phases. There is considerable oxygen pickup during the intermediate annealing cycles, but the increased oxygen has not deleteriously affected room-temperature tensile ductility.