Effect of pre-annealing deformation on thermally activated twin boundary migration in a zirconium alloy

Uniaxial compression along the rolling direction was conducted in a Zr-4 alloy sheet to induce twinning followed by annealing at various temperatures. The microstructure and texture before and after static annealing were investigated by electron backscatter diffraction (EBSD) to evaluate the possibility to tailor the recrystallized microstructure and texture of Zr alloys by pre-twinning and annealing. It is worth to note that microstructure and texture affect the performance of Zr alloys, for instance corrosion resistance, creep and delayed hydride cracking. During annealing, the twins show relative thermostability in the sample with a low pre-annealing deformation (5%), whereas obvious thermally activated twin boundary migrations start at a relative low temperature (650 °C) in the sample with a large pre-annealing deformation (20%). The texture induced by twinning was further strengthened during recrystallization annealing as a result of the increase in the twin area fractions. More coherency losses and a higher diving force in the sample with a larger pre-annealing deformation may help to induce twin boundary migration at lower annealing temperatures.