Unveiling the interface fracture mechanism dominated by intermetallic compounds during tensile deformation of copper/aluminum composite thin strips

In the present work, the complex failure mechanism dominated by intermetallic compounds (IMCs) of copper/aluminum (Cu/Al) composite thin strips (CTSs) during tensile deformation was studied. A series of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron back-scattered diffraction (EBSD) tests were employed to analyze the interfacial morphology, crack formation, and microstructural evolution of Cu/Al CTSs during the tensile process. After annealing at 450 °C for 1 h, the IMCs layer reached a total thickness of 18 μm, comprising three sublayers: θ (CuAl₂), η₂ (CuAl), and γ₁ (Cu₉Al₄). The results of uniaxial and in-situ SEM tensile tests revealed that the initial cracks during the low strain stage occur at the Al/CuAl₂ interface (IMCs cracks and Al cracks), with IMCs cracks originating in the CuAl₂ layer and extending into CuAl and Cu₉Al₄ layers. The fluctuating increase in tensile stress can be attributed to the emergence of IMCs cracks, which leads to instantaneous stress reductions, followed by local dislocation strengthening due to the widening of IMCs cracks. In addition, local stress concentrations induced by widening IMCs cracks lead to grain orientation rotation, activating additional slip systems and transitioning from hard to soft orientations.