Effect of temperature on the tensile deformation behavior and fracture mechanism of a transient liquid-phase bonding joint of gamma'-strengthened Co-based single-crystal superalloy

摘要

Tensile behavior at different deformation temperature of a transient liquidphase (TLP) bonded joint of gamma'-strengthened Co-based superalloy was investigated. A temperature dependence phenomenon of the joint's fracture position was found, which transferred from the base metal to the bonding area with increase in the temperature, and this is related to the deformation mechanism. At room temperature, dislocation shearing the gamma' phases in different areas of the joint domains the deformation and makes it heterogeneous, and more deformation has occurred at the BM because of lower content of gamma' phase, which makes the failure occurred at the BM. The deformation mechanism gradually transferred from dislocation shearing to bypassing the gamma' with increasing the temperature, making the deformation become diffused, and this can lead to the fracture of the joint's brittle borides, and the coalescence of the boride-induced cracks makes the fracture occur at the diffusion affect zone at 600 degrees C similar to 900 degrees C. As the secondary-gamma' in the joint's isothermal solidification zone dissolves at 1000 degrees C, more deformation occurs there and the accumulation of micro-voids induced by the dislocation climbing leads to the fracture.