On the twinning shear of [formula omitted] twins in magnesium – Experimental determination and formal description.

Specifically oriented Mg single crystals, aligned for c -axis extension, were deformed in channel-die plane strain compression in order to form { 10 1 ¯ 2 } extension twins. The amount of twinning shear for { 10 1 ¯ 2 } twins was determined directly from the deflection of marker lines to be s = 0.126 , in excellent agreement with the theoretical value. The twinning shear was discussed with respect to the shear-coupled grain boundary migration by analyzing the formal dislocation content of { 10 1 ¯ 2 } twin boundaries. The respective boundary migration – shear coupling factor is proposed to result from a combination of two elementary coupling modes, 〈 10 1 ¯ 0 〉 and [ 0001 ] . [ABSTRACT FROM AUTHOR]