Laminated/bimetal composites can offer the advantage of combining constituent metals, but their heterogeneous microstructures exhibit different mechanical properties during subsequent remanufacturing process than those of the homogeneous counterparts. This study investigated the tensile properties, microstructural evolution and deformation behaviours of a new explosive welded TA1/5083 composite sheet using the in-situ characterisation. It is found that a wavy transition zone forms in the composite sheet, showing gradients in the element diffusion and micro-hardness adjacent to the interface. The slip bands with the tensile direction of 45�� primarily occur in the 5083 side (rather than the TA1 side) with an increase in deformation. Although the dislocation density of the grains in the 5083 layer increases significantly, these grains are slightly elongated along the tensile direction without a significant orientation change. Three deformation stages and a subsequent crack initiation stage appear during the in-situ tensile process. The initiation of micro-cracks in the interfacial zone results from the internal stress concentration occurring at the bottom of interfacial wave structure. Once initial micro-cracks evolve into the intermetallic compounds (IMCs) of the interfacial zone, the high magnitude of stress concentrations of the TA1 and 5083 layers leads to necking and sequential fractures. This study can provide a reference for the design of high-quality Ti/Al composite components for industry.