Recrystallization mechanisms of Zircaloy-4 alloy annealed by electric current

Abstract

In this paper we present recrystallization mechanisms in Zircaloy-4 alloy subjected to electric current annealing while maintaining the surface temperature below 135 °C. Electron backscatter diffraction (EBSD) was used to characterize and study the evolution of the microstructure and microtexture. We observed a continuous dynamic recrystallization (cDRX), and full recrystallization was achieved at a current density of 5x106 A/mm2. This was attributed to the synergistic effects of athermal (electron-wind force) and thermal (Joule heating) analogous to the effects of deformation strain and temperature during warm/hot working process. While the boundary density and fraction of low-angle grain boundaries decreased with current density, a gradual increase in the fraction of high-angle boundaries was noted. The dominant recrystallization mechanism was volumetric rotation-coalescence-induced grain growth. The <0001>//z microtexture of electric current annealed Zr-4 alloy remained virtually the same before and after recrystallization and was attributed to the grain rotational mechanism. These results show the potential of using this process for tailoring the microstructure and grain boundary engineering while retaining the desired texture.