Quasi-in-situ EBSD study on tensile twinning activity caused by dynamic loading for extrusion-shear ZCW610 alloy

Abstract

In this work, the twinning behavior of extruded ZCW610 alloy at room temperature was investigated during dynamic compression along extrusion direction (ED) by quasi-in-situ electron backscattering diffraction (EBSD). Statistics found that $\left(10\overline{1}2\right)$ tensile twins are mainly formed and the volume fraction of twins tends to increase with increasing strain. The nucleation and growth of twins often occur at 3.5 % and 6.5 % strains in the early stages of deformation. The quasi-in-situ EBSD studies shown that most $\left(10\overline{1}2\right)$ tensile twins formation are comply with Schmid's law. A large number of the “paratactic” and same orientation $\left(10\overline{1}2\right)$ tensile twinning formed in single grain during dynamic compression are initiated by the same twin variants with highest Schmid factor (SF). Meanwhile, multiple “paratactic” or “non-paratactic” twins with different orientation occurred within some grain are general adjacent twin variants with high SF. Especially, the selection of twin variants with low SF is not comply with Schmid's law, which related to the strain compatibility factor (m’) in order to release local stress during dynamic loading. The study also showed that twinning generated by strain compatibility factors is prone to forming twin pairs or twin chains in the neighboring grains to accommodate the plastic deformation.