Unusual shear induced unconventional [formula omitted] twinning in Mg

Abstract

Conventional (1¯011) twinning in hexagonal metals has the twin plane K1 = (1¯011) and the corresponding twinning direction η1=[1¯012¯]. Twinning shear is generally accomplished through the gliding of two-layer and/or four-layer twinning dislocations (TDs) along η1 associated with atomic shuffles. Using molecular dynamics simulations, we reveal that an unusual shear along −η1 associated with atomic shuffles on the twin plane K1 is resulted by gliding of a one-layer TD. Correspondingly, an unconventional {1¯011} twinning occurs through successive gliding of one-layer TDs. Such a twinning mechanism is found to be correlated to high stress/strain concentration, such as at crack tip.