Achieving strong interface bonding in CuAl/Fe bimetal laminated composites via tailoring an ordered large-scale interlocking structure

Tailoring large-scale interlocking structures is one of the most reliable methodologies for enhancing the bonding strength of heterogeneous interface. In this investigation, the continuous solid-liquid bonding method was employed to prepare Cu-7Al/DT4 bimetal laminated composites featuring an interlocking structure interface. Furthermore, the formation mechanism of interfacial intergranular penetrations was also elucidated using microstructure observation, mechanical property tests, thermodynamics, molecular dynamics and density functional theory calculation. It is found that an interlocking structure layer with a thickness of about 20 μm is formed between Cu-7Al and DT4, with a bonding strength exceeding the shear strength of Cu-7Al (about 250 MPa) alone. The type and concentration of solute atoms, and insulation period are proposed to be the key factors influencing the formation of intergranular penetrations. Besides, the formation of the ordered large-scale interlocking structure is primarily attributed to the structural transformation of Fe, surface diffusion, grain boundary/volume diffusion, Marangoni effect and interface/grain boundary migration. Tailoring intergranular penetrations can counteract the barrier of interfacial oxides, enabling a strong bonding of the interface. More importantly, apart from Cu-7Al/DT4, such a type of large-scale intergranular penetrations has also been achieved in Cu-Sn and Cu-Zn systems, strongly indicating that it is indeed a reliable approach for bimetal laminated composites. This investigation provides a streamlined approach for preparing various bimetal laminated composites with a strong interface and develops the foundation for designing novel bimetal laminated composites.