Nucleation and growth analysis of [formula omitted] extension twins in AZ31 magnesium alloy during in-situ tension

Abstract

The in-situ tensile test combined with electron back-scattering diffraction (EBSD) method is carried out to observe the nucleation and growth of {101‾2} extension twins in AZ31 magnesium alloy. The dynamic process of twinning can be clearly revealed by tracing the same position in the process of increasing of cumulative strain. According to the statistical analysis results, which are based on a large number of data set, Schmid Factor (SF) plays an important role in the nucleation and growth of twins. The twin variants with high SF are easier to activate and have a relatively high growth rate. However, not all the twins follow the SF rule. About 60% of the nucleated twins during the in-situ tensile test satisfy the SF rule, while for the twin growth this number is decreased to 50%. In addition, the strain accommodation factors between the deformation modes in neighboring grains and extension twins are analyzed. The shear accommodation for extension twins nucleation and growth in neighboring grains plays an important role. The shear accommodation imposed by pyramidal slip in the neighboring grains is beneficial to the twin nucleation, however, is unfavorable for the twin growing.