Basal slip in the long-period stacking-ordered (LPSO) phases in the Mg–Zn–Y ternary system

Influences of the stacking sequence and in-plane ordering of Zn₆Y₈ atomic clusters on the basal slip in long-period stacking-ordered (LPSO) phases in the Mg-Zn-Y systems were investigated by micropillar compression of single crystals at room temperature. The critical resolved shear stress (CRSS) values for basal slip do not depend much on the stacking sequence of the LPSO structures and the degree of the in-plane ordering of Zn₆Y₈ atomic clusters. The CRSS values increase with the decrease in the specimen size, following an inverse power-law relationship with a very large power-law exponent of about 0.88. Atomic-resolution scanning transmission electron microscopy (STEM) imaging of core structures of basal edge dislocations in the Mg-Zn-Y LPSO phase with a perfect in-plane ordering of Zn₆Y₈ atomic clusters revealed that the Burgers vector is <b>b</b> = (<i>a</i>/3)[2 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover><mml:mn>1</mml:mn> <mml:mo>-</mml:mo></mml:mover> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover><mml:mn>1</mml:mn> <mml:mo>-</mml:mo></mml:mover> </mml:math> 0] and the basal dislocations glide between the atomic planes which do not cut through Zn₆Y₈ atomic clusters.