In situ characterization of lattice structure evolution during phase transformation of Zr-2.5Nb
The α–β phase transformation behavior of Zr-2.5Nb (in mass%) has been characterized in real time during an in situ neutron diffraction experiment. The Zr-2.5Nb material in the current study consists, at room temperature, of α-Zr phase (hcp) and two β phases (bcc), a Nb rich β-Nb phase and retained, Zr rich, β-Zr(Nb) phase. It is suggested that this is related to a quench off the equilibrium solubility of Nb atoms in the Zr bcc unit cells. Vegard's law combined with thermal expansion is applied to calculate the composition of the β-phase, which is compared with the phase diagram, revealing the system's kinetic behavior for approaching equilibrium.