Reversible twinning in high stacking-fault energy aluminum was reported. Twinning and spontaneous de-twinning at the crack tip were captured in situ during tensile straining under a transmission electron microscope. Both the in situ observation and the molecular dynamics simulations reveal a two-stage de-twinning process. The high propensity for de-twinning was due to the high stacking fault energy and the low frictional forces against the de-twinning partial dislocations in Al. This discovery of reversible twinning has implications for the deformation of other high stacking fault energy materials.

Reversible Twinning in Pure Aluminum. B.Q.Li, M.L.Sui, B.Li, E.Ma, S.X.Mao: Physical Review Letters, 2009, 102[20], 205504