α→β Transformation characteristics revealed by pulsed laser-induced non-equilibrium microstructures in duplex-phase Zr alloy

Abstract

Microstructures of a duplex-phase Zr-2.5Nb alloy treated by pulsed laser were characterized by electron backscatter diffraction (EBSD) and electron channeling contrast (ECC) imaging techniques. Major attention has been paid to non-equilibrium hybrid microstructure consisting of both prior α and β phases, and α plates transformed from new β phases to probe α→β transformation characteristics in the alloy. The origin of the hybrid microstructure is attributed to the specific thermodynamic conditions induced by the pulsed laser treatment. ECC observation shows that newly formed β phases during laser heating prefer to nucleate and grow at the expense of edges of prior α grains rather than their interiors. EBSD analyses further reveal that orientations of the new β phases are not determined by the prior α grains according to the Burgers relationship but maintain those of the prior β phases in an epitaxial growth way.