Study on interfacial microstructure and shear strength of hot-compression bonded Ti386/TC4

The hot-compression bonding of Ti386 and TC4 titanium alloys takes place within a temperature range of 800 to 900 °C and under strains of 10–30% in this study. The analysis of Ti386/TC4 joints involves the interfacial microstructure and compression shear strength are conducted. Quantitative analysis reveals that the interfacial voids, as a consequence of surface roughness, notably decrease as deformation strains and temperatures increase, which leads to the highest shear strength 673.26 MPa at 900 °C/30%. The Ti386/TC4 interface exhibits distinct characteristics and presents two zones: α_p(TC4)/β_(Ti386) and α_s + β_(TC4)/β_(Ti386). The α_p(TC4) phase protrudes into the β_(Ti386) side at the α_p(TC4)/β_(Ti386) interface due to the higher hardness of the stable primary α_p(TC4). During the process of deformation bonding, dynamic recrystallization occurs within the interfacial region. On the TC4 side, dynamic recrystallization is primarily discontinuous dynamic recrystallization, initially observed in the lamellar α_s + β areas before extending to the equiaxed α_p areas. Conversely, on the Ti386 side, continuous dynamic recrystallization prevails, characterized by the transformation of low-angle grain boundaries to high-angle grain boundaries.