Interface microstructure and strength properties of Ti-6Al-4V and microduplex stainless steel diffusion bonded joints

The diffusion bonding of Ti-6Al-4V alloy and micro-duplex stainless steel was carried out in the temperature range of 850-1000 degrees C for 45 min in vacuum. The influence of bonding temperature on the microstructural development, micro-hardness and strength properties across the joint region was determined. The layer wise sigma phase, lambda + FeTi and lambda + FeTi + beta-Ti phase mixtures were observed at the bond interface when the joint was processed at 900 degrees C and above temperature. The maximum tensile strength of similar to 520.1 MPa and shear strength of similar to 405.5 MPa along with 6.8% elongation were obtained for the diffusion couple processed at 900 degrees C. Fracture surface observation in scanning electron microscopy (SEM) using energy dispersive X-ray spectroscope (EDS) demonstrates that, failure takes place through lambda + FeTi phase when bonding was processed at 900 degrees C, however, failure takes place through sigma phase for the diffusion joints processed at and above 950 degrees C. (C) 2011 Published by Elsevier Ltd.