Plastic deformation behavior of Mg89Zn4Y7 extruded alloy composed of long-period stacking ordered phase

The deformation behavior of an Mg89Zn4Y7 (at.%) extruded alloy composed mostly of the long-period stacking ordered (LPSO) phases, was investigated at room temperature. Several heat-treatments were conducted for the extruded alloy in the temperature range between 400 and 525 degrees C, and the correlation between the microstructure and the mechanical properties were quantitatively examined. The yield stress of the as-extruded alloy showed extremely high value of similar to 480 MPa. The deformation of the as-extruded alloy proceeded accompanied by the formation of deformation kinks and small amounts of non-basal slips. The microstructure of the extruded alloy was highly thermally stable and the yield stress showed little change by heat-treatments below 400 degrees C. However, the yield stress was gradually decreased by annealing above 400 degrees C. The yield stress of the alloys annealed at and above 475 degrees C showed discontinuous decreases with increasing annealing temperature. The yield stress of the annealed specimens could be estimated by the Hall-Petch relationship by regarding the length of the long-axis of plate-like grains as the grain size. This suggests that the basal (0001) slip governed the plastic behavior of the LPSO-phase alloy composed of randomly oriented grains. (C) 2010 Elsevier Ltd. All rights reserved.