Ultrastrong and ductile transient liquid phase (TLP) bonding joints reinforced by ordered multi-precipitates

Transient liquid phase (TLP) bonding of is one of the most important welding technique to be applied to manufacture core components of aero-engine turbines. Homogeneous microstructure in a TLP joint with no defects and brittle products has always been the goal we pursued. But actually, this is far from the requirements for a superior-performance, long-life and excellent-reliability turbine as the joints need to be serviced with comprehensive properties such as high strength and toughness, outstanding creep resistance and so on. In this work, an ultrastrong and ductile TLP joint of high entropy alloy (HEA) of FeCoNiTiAl and FGH98 superalloy has been achieved by controlling ordered multi-precipitates, L1₂-Ni₃Al, TiB₂ and M₃B₂ borides, produced in the welded zone. Formation and growth kinetics of the precipitates were characterized by atom probe tomography (APT), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). Furthermore, a microstructure-based finite element model (FEM) combined with the TEM analysis were applied to study plastic deformation mechanisms of TLP joint with maximum shear stress of 1156 MPa and excellent ductility (an abundance of dimples in fracture surface). As a result, the superb joint performance was due to competition and coordination of multi-precipitates. This work offers a new technological paradigm to develop the aero-engine manufacturing industry for engineers and designers.