Interfacial microstructure evolution and bonding mechanisms of 14YWT alloys produced by hot compression bonding

Abstract

Hot compression bonding was first used to join oxide-dispersion-strengthened ferrite steels (14YWT) under temperatures of 750–1100°C with a true strain range of 0.11–0.51. Subsequently, the microstructure evolution and mechanical properties of the joints were characterized, revealing that the 14YWT steels could be successfully bonded at a temperature of at least 950 °C with a true strain of 0.22, without degrading the fine grain and nanoparticle distribution, and the presence of inclusions or micro-voids along the bonding interface. Moreover, the joints had nearly the same tensile properties at room temperature and exhibited a similar fracture morphology with sufficient dimples compared to that of the base material. An electron backscattered diffraction technique and transmission electron microscopy were systematically employed to study the evolution of hot deformed microstructures. The results showed that continuous dynamic recrystallization characterized by progressive subgrain rotation occurred in this alloy, but discontinuous dynamic recrystallization characterized by strain-induced grain boundary bulging and subsequent bridging sub-boundary rotation was the dominant nucleation mechanism. The nuclei will grow with ongoing deformation, which will contribute to the healing of the original bonding interface.