Deformation Behavior of Long-Period Stacking Ordered Structured Single Crystals in Mg85Zn6Y9 Alloy

Microtension tests were performed on single crystals with different crystallographic orientations, which were prepared using an 18R-type long-period stacking ordered (LPSO) structure in a directionally solidified Mg85Zn6Y9 alloy. Anisotropic plasticity was observed for the LPSO phase specimens. Cleavage cracking occurred on the prismatic planes in a crystal with its loading direction parallel to the basal plane. The cleavage stress for the prismatic plane was determined to be approximately 460 MPa. A crystal that was oriented favorably for gliding on the basal plane exhibited a critical resolved shear stress of approximately 9.4 MPa. When a crystal was loaded along [0001], a sudden load drop was observed at a stress of approximately 250 MPa in the initial linear region of the stress-strain relation. Transmission electron microscopy results after the load drop showed that the deformation microstructure contained a twin-like boundary with a rotation axis along [11 (2) over bar0].