Deformation structure in rapidly solidified Mg97Zn 1y2 alloy with long period stacking order phase

Deformation structure in rapidly solidified Mg₉₇Zn ₁Y₂ ribbon with the long period stacking order (LPSO) phase is investigated by conventional transmission electron microscopy to understand the interaction between the LPSO phase and lattice defects. In the grain with the LPSO phase there are no a dislocations lying on the basal plane, and a number of c + a dislocations are visible. On the other hand, in the grain without the LPSO phase there are many straight a dislocations lying on the basal plane. These facts indicate that the critical resolved shear stress of the basal plane increases by the formation of the LPSO phase and the non-basal slip is activated by the prevention of the basal slip. In other words, the former directly contributes to the strengthening and the latter relates to the improvement of ductility with the increment of the slip system. Therefore, it is concluded that the LPSO phase plays a unique role which enhances the conflicting properties of strength and ductility in the mechanical property of the present alloy. The densely developed LPSO phase prevents the growth of {101̄2} deformation twin in Mg matrix. This indicates that the LPSO phase contributes to the strengthening of this alloy. On the other hand, the LPSO phase with low density cannot be the resistance of the twinning. The trace of basal plane in such LPSO phase deviates with constant angle of about 3.8 degrees at the twin boundary. This angle is well explained by the atomic movement with shuffling in the formation of {101̄2} twin.