Homogenization treatment-induced reduction of brittle intermetallic compounds in Ti2AlNb/Ti60 brazed joints: Effect on microstructure and mechanical properties

The microstructure evolution and mechanical properties of Ti2AlNb/Ti-36.5Zr-10Ni-15Cu-0.5Co-0.5Nb/Ti60 brazed joints before and after homogenization treatment were comprehensively evaluated. Initially, the joints brazed at 900 degrees C for 15 min exhibited a continuous coarse strip network of Ti2Cu, Ti2Ni, Zr2Cu and Zr2Ni brittle intermetallic compounds in the central region of the braze seam, which detrimentally affecting the mechanical properties. Subsequent homogenization at 600 degrees C for 1 h, the amount of continuous brittle intermetallic compounds significantly decreased through sufficient atomic diffusion. Concurrently, the inadequately transformed eutectic beta-Ti within the intermetallic compounds underwent an active eutectoid reaction. This structural transformation established a coherent interface with elastic distortion between the alpha-Ti and intermetallic compounds, effectively minimizing the lattice mismatch. Thus, a widmanstatten structure (i.e., acicular intermetallic compounds within a eutectoid microstructure matrix) with improved mechanical properties was formed. Consequently, a mean shear strength of 350.3 MPa was attained after treatment at 600 degrees C for 1 h, marking a substantial 206 % increase compared to that before homogenization treatment. This finding underlines the pivotal role of homogenization treatment in optimizing the performance of aeroengine components.