Experimental studies on detwinning of face-centered cubic deformation twins

An experimental proof of the existence of three different detwinning modes of face-centered cubic deformation twins was performed. This proof was achieved through specially designed tests of primary and secondary deformation of copper-aluminum alloy single crystals that were pre-twinned and then consecutively de-twinned in a strictly controlled manner. The different detwinning modes were found as the main plastic strain mechanisms operating during different deformation paths of secondary tension or compression. One of the modes was associated with reverse twinning that is able to cancel both of the effects induced by primary deformation twinning, which means a change of crystal shape and crystal orientation. The two other modes were capable of canceling the effect of crystal orientation only; therefore, they were recognized as pseudo-reverse twinning modes. It was also found that the critical stress of the detwinning mode consisting of the reverse twin shear was lower than those of the pseudo-reverse twinning modes by a factor of two, and even lower compared to the value of the critical stress of primary deformation twinning. Two alternative suggestions have been made to explain the observed differences in the critical stresses of the detwinning modes associated with the reverse and pseudo-reverse modes of deformation twinning.

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