Microstructural and Mechanical Characterization of TiAl/Ti6242 Diffusion Bonds

Abstract

Ti-6242 alloys have been widely used in aero-engine applications due to high temperature strength and creep resistance. The γ-TiAl based intermetallics are considered as candidate materials to replace the current materials weed at high temperatures. The present paper reports on the microstructural and mechanical characterization of γ-TiA/Ti6242 diffusion bonds. The emphasis is put on the better understanding of microstructural development during diffusion process and mechanical properties of diffusion bonds. The process variables of temperature, pressure and time were optimized to produce joints with sound microstructure and bond quality for mechanical characterization. The micro and standard tensile tests were applied to determine bonding strength of joints. Metallographic and fractographic examinations on diffusion joints and tested specimens were carried out using SEM coupled with EDX. The concentration profiles of elements from EDX analysis combined with SEM/BSE investigation demonstrated that the strong inter-diffusion of main elements Al and Ti across the bonding interface occurred during DB process leading to the formation of a noticeable diffusion zone consisting of fine* α2/α grains. The micro tensile tests showed that the preference of fracture on base materials far from the bonding line, but a more marked tendency to brittle failure along bonding interface shown by the standard tensile test results, indicating a significant sample size effect on mechanical property measurements.