Influence of bonding time during diffusion bonding of Ti–6Al–4V to AISI 321 stainless steel on metallurgical and mechanical properties

Abstract

Diffusion bonding was employed to join AISI 321 stainless steel to Ti–6Al–4V titanium alloy via Cu–Zn foil as the interlayer. The influence of bonding time (30, 45 and 60 min) at 900 °C temperature with the pressure of 2 MPa on the microstructural and mechanical behaviors of the joints is evaluated. The optical and scanning electron microscopes were utilized to examine the microstructural characteristics of the Ti–6Al–4V/Cu–Zn/AISI 321 stainless steel joints. Results displayed that three distinct reaction layers have been created as a result of the brazing process at all joints. It was also found that a longer bonding time led to the widening/expanding of the reaction/diffusion layers. The attained data also showed that bonding time affected the formation of brittle IMCs including CuTi2, CuTi, FeTi, Fe22Zn78 and TiZn3 phases within the interface as a result of the increased diffusivity of reaction elements and subsequently resulted in the reduction of the shear strength of the diffusion bonded joints from 281 MPa for bond made at 30 min to about 174 MPa for bond made at 60 min. Decreasing the shear strength by rising the bonding time can be a sign of expanding the level of interfacial reaction at the joints.