The coordinated evolution behavior of interface microstructure regulation and bonding strength of hot-spinning Mg/Al composite tubes under annealing

• The evolution behavior of the interface diffusion layer of Mg/Al composite tube was clarified. • The coordinated evolution mechanism of interface microstructure and shear strength of Mg/Al composite tube was clarified. • The evolution of microstructure and texture of Mg/Al composite tube under annealing process was clarified. • The twin-induced recrystallization mechanism of Mg alloy during annealing was revealed. • The growth and proliferation behavior of the grain structure of the IMCs layer is driven by the element migration to complete its directional growth process. In this study, Mg/Al bimetallic composite tubes (BCTs) were successfully fabricated using the hot power spinning (HPS) process, and the width of the interface diffusion zone was effectively controlled by adjusting the annealing time and temperature. The shear fracture mechanism and microstructure evolution of the Mg/Al BCTs were investigated using various microscopic characterization techniques and mechanical tests. The results showed that as the diffusion zone length increased from 6.27 µm to 18 µm, the shear strength improved from 14.21 MPa to 26.89 MPa. However, when the diffusion band was further expanded, a brittle intermetallic compound (IMC) layer, composed of Mg 17 Al 12 and Al 3 Mg 2 , formed, which reduced the interfacial bonding strength. When the annealing temperature was raised to 400 °C, a Kirkendall void layer developed at the interface, decreasing the shear strength to 4.32 MPa. On the Al side, static recrystallization significantly reduced the grain size, and a more pronounced Goss texture appeared. On the Mg side, a large number of abnormally grown grains were continuously broken down into finer grains under the influence of annealing twins, and the c-axis of the grains showed significant alignment in the rolling direction (RD). When the diffusion layer formed Mg 17 Al 12 and Al 3 Mg 2 , the interface exhibited a distinct equiaxed crystal morphology, and the grains grew radially along with the expansion of the IMCs. These findings enhance the understanding of the manufacturing process of Mg/Al BCTs and provide valuable insights for regulating the interface structure and bonding strength of Mg/Al BCTs.