Homogenization Treatment-Induced Reduction of Brittle Intermetallic Compounds in Ti2alnb/Ti60 Brazed Joints: Effect on Microstructure and Mechanical Properties

Abstract

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. Before homogenization treatment, joints brazed at 900 °C for 15 min displayed a continuous coarse strip network of (Ti, Zr)2(Cu, Ni) brittle intermetallic compounds in the central region of the braze seam, negatively impacting mechanical properties. After homogenization treatment at 600 °C for 1 h, the continuous brittle intermetallic compounds decreased significantly. Concurrently, the inadequately transformed eutectic β-Ti within the intermetallic compounds underwent active eutectoid reaction. This structural transformation established a coherent interface with elastic distortion between the α-Ti phase and intermetallic compounds phase, effectively minimizing the lattice mismatch. A widmanstatten structure (i.e., acicular intermetallic compounds within a eutectoid microstructure matrix) with improved mechanical properties was thus formed. Consequently, an average shear strength of 350.28 MPa was achieved after treatment at 600 °C for 1 h, marking a substantial 206% increase compared to the shear strength of the brazed joints before homogenization treatment. This underscores the critical role of homogenization treatment in improving the performance of the components in aero-engines.

Keywords: Brazed joint, Homogenization treatment, Active eutectoid, coherent interface, Mechanical properties