Microscale deformation of an intermetallic-metal interface in bi-layered film under shear loading

While hetero-interfaces in materials are critical for tuning mechanical properties, they can also act as failure sites, underscoring the importance of determining their strength. This study reports on a novel single-shear micro-geometry, and demonstrates its applicability for testing the strength and deformation of hetero-interface in bi-layered films in a direct manner. The shear tests are applied to a model CaMg₂-Mg bi-layered system grown by magnetron sputtering, comprising of a CaMg₂ film deposited onto a Mg layer. A parametric study was performed using finite element modeling to optimize the specimen dimensions. Subsequently, in situ microshear tests conducted inside a scanning electron microscope revealed interface shear strength of ∼129 $\pm$ 12 MPa, and provided insights into the stages of deformation progression from elastic behavior to interface sliding, accompanied by plasticity in Mg near the interface. Post mortem examination of the sheared interface revealed irregular surface indicating ductile deformation at room temperature.