In-situ observation on the twinning boundary movement of pure zirconium during three-point bending tests

The movements in two directions of the boundary between twinning variants and matrix were firstly reported using in-situ electron backscatter diffraction (EBSD) during continuous three-point bending tests in nuclear grade pure zirconium. With the combination of schmid factors and the three dimensional model of identified twinning variants, the mechanism of the twinning boundary movement was proposed by follows: twinning {10–12} variants and tensile twinning {11–21} were formed during the first three-point bending test. After that, the matrix moves along the twin boundary through activated PR (prismatic {10-10}) with the further growth of twinning {10–12} variants and tensile twinning {11–21} in the next bending test, resulting in the movements in two directions of the boundary between twinning variants and matrix. Moreover, a new atomic model showing the movement of the twinning boundary was proposed.