Microstructure and fractography of Ti/Al laminated composite processed by solid state diffusion bonding and annealing treatment

Amir Hossein Assari¹ Beitallah Eghbali²

1) Department of Materials Science and Engineering, Sahand University of Technology, Tabriz, Iran
2) Department of Materials Science and Engineering, Sahand University of Technology, Tabriz, Iran

IOI Code : XDHC-FEZAH
Publication : 3rd International Congress On Engineering, Technology and Innovation(eticong.com/3rd)
Abstract :
    Recently, there has been a remarkable interest in Ti/Al laminated composites because of their high strength and low weight structures. This article explores the synthesis of Ti/Al laminated composites through diffusion bonding including hot pressing (applied under the compression stress of 40 MPa at 570 °C for 1 hour) and hot rolling (applied at about 450 °C to 30% and 57% thickness reduction). The effects of annealing temperatures (550, 600 and 650 °C) and times (2, 4 and 6 hours) on microstructures and fracture surfaces have been studied. The results of X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS) confirmed that TiAl3 is the only intermetallic compound detected at the interface of Ti/Al layers. In addition, based on the results of the scanning electron microscope (SEM), the thickness of TiAl3 layer increased with the increase in both annealing temperature and time. Also, it is interesting to note that the thickness of TiAl3 compound increased when strain hardening increased, and then the growth behavior of the intermetallic compound changed from linear to parabolic. The characterization of Al and Ti sides of fracture surfaces indicated that a high amount of dimples was concentrated at the center of necked regions and the ductile fracture occurred in original patterns of Ti and Al layers. Furthermore, the TiAl3 compound grew and original patterns of Al and Ti disappeared when annealing temperatures and times increased. The results showed that intergranular fracture took place in TiAl3 compound with rock-candy appearance.

Keywords : diffusion bonding annealing fracture intermetallic compound microstructure