Kink-band formation in directionally solidified Mg/Mg2Yb and Mg/Mg2Ca eutectic alloys with Mg/Laves-phase lamellar microstructure

For the development of high-strength Mg alloys, active use of Laves phases such as C14-type Mg2Yb and Mg2Ca is strongly expected. However, the brittleness of the Laves phases is the biggest obstacle to it. We first found that kink-band formation can be induced in directionally solidified Mg/Mg2Yb and Mg/Mg2Ca eutectic lamellar alloys when a stress is applied parallel to the lamellar interface, leading to a high yield stress accompanied with ductility. That is, microstructural control can induce a new deformation mode that is not activated in the constituent phases, thereby inducing ductility. It was clarified that the geometric relationship between the operative slip plane in the constituent phases and the lamellar interface, and the microstructural features that provide kink-band nucleation sites are important factors for controlling kink-band formation. The obtained results show a possibility to open the new door for the development of novel high-strength structural material using the kink bands.