Structure of orthorhombic martensitic phase in binary Ti–Nb alloys

Abstract

The structure of orthorhombic (α″) martensitic phase of Ti–8Nb, Ti–12Nb, and Ti–16Nb alloys has been investigated using Rietveld refinement of x-ray diffraction data. The chemical analysis data have been used to determine the site occupancy of initial models. A limit of the Wyckoff positions has been proposed based on the symmetry of the Cmcm space group, which allows the movement of atoms without breaking the space group symmetry. This has also been incorporated in the initial models of experimental alloys, and accordingly Wyckoff positions have been refined. It has been observed that the atoms move along the Y-axis (parallel to the b-axis) and the movement of atoms increases with increase in Nb concentration. The formation of orthorhombic (α″) phase has been explained based on the movement of atoms along the Y-axis. This in turn breaks the hexagonal symmetry and forms an orthorhombic phase.

Influence of phase transformation kinetics on the formation of α in a β-quenched Ti–5Al–5Mo–5V–3Cr–1Zr alloy

“…10(b)). In parallel to these variations, Rietveld analysis revealed an increase in the atomic y-coordinate of the crystal structure of a 00 from 0.180 to 0.196 (see Table 3), denoting a continuous increase in the solute content of this phase [21,66]. These effects together with the fact that at this stage of the heating the volume fraction of a 00 iso + a increases while that of b decreases (Fig.…”

Effect of the substitutional elements on the microstructure of the Ti-15Mo-Zr and Ti-15Zr-Mo systems alloys

“…Corrosion of this type occurs in chemical etching of polished surfaces, being favored by internal tensions on the surface, creating regions where chemical kinetics of the reaction is accelerated. The predominance of grains of the ␤ phase, with the absence of acicular structures concerning ␣ and ␣ phases, can also be seen [22]. In Fig.…”

Design and tensile properties of a bcc Ti-rich high-entropy alloy with transformation-induced plasticity

“…Considering the close relationship between the orthorhombic lattice and a hexagonal one, [28] this relation described in the latter structure would be a rotation of 80°along −1101 , which corresponds to a 10-1-2 {10-11} twin. Smaller magnifications indicate that up to three different orientations of martensite can be observed in each former β grain.…”