Enhancing interface bonding strength of Ti/Al laminated composites via periodic surface nano-crystallization pretreatment

Ti/Al laminated composites have high strength and excellent corrosion resistance, while the relatively low interface bonding strength has still restricted its wide usage. This paper proposes a new method to improve the interface bonding strength of Ti/Al laminated composites through surface nano-crystallization pretreatment using ultrasonic rolling technique. The mechanical property, interface characteristics and interface bonding mechanism are thoroughly studied. The results show that ultrasonic rolling surface pretreatment enables the strong interface bonding of Ti/Al laminated composites and greatly reduces the rolling reduction threshold. It is revealed that ultrasonic rolling surface pretreatment can generate periodic grooves and nanocrystalline layer with low ductility on the Ti surface, which can effectively promote cracking of the Ti hardening layer and increase the contact area of virginal Ti and Al metals during rolling process. Besides, ultrasonic rolling forms nanocrystals and high-density defects on the top surface of the titanium layer, which promote the migration, exchange and rearrangement of atoms under severe plastic deformation and eventually lead to the formation of amorphous structures in the transition layer of the Ti/Al interface. Therefore, the Ti/Al laminated composites pretreated using ultrasonic rolling technique exhibit outstanding interface bonding strength, especially at relatively low rolling reduction conditions.