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

• The complex failure mechanism dominated by intermetallic compounds of copper/aluminum composite thin strips during tensile deformation was studied. • Al cracks along the grain boundary and cracks through the IMCs layer occur at the Al/CuAl 2 interface at low strain, and the IMCs cracks originate in the CuAl 2 layer and extend into CuAl and Cu 9 Al 4 . • As IMCs cracks widen, the internal orientation of grains near the crack tip undergoes rotation, thereby manifesting as a transition from hard to soft orientations. 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 (CuAl 2 ), η 2 (CuAl), and γ 1 (Cu 9 Al 4 ). The results of uniaxial and in-situ SEM tensile tests revealed that the initial cracks during the low strain stage occur at the Al/CuAl 2 interface (IMCs cracks and Al cracks), with IMCs cracks originating in the CuAl 2 layer and extending into CuAl and Cu 9 Al 4 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.