Multiple self-exothermic reactions for room-temperature aluminum bonding via instantaneous melting

Abstract We propose a room-temperature multiple-reaction bonding method for aluminum, by combining the thermite reaction of Al-CuO powder and self-propagating formation reaction of Ti-B powder with no external heat source. The joint microstructure consists in various composites (Al 2 O 3 , TiB 2 and Al-Cu intermetallic), and their distribution affects the joint bonding properties. The multiple reaction leads to a compact joint layer with a very low porosity, in contrast to joints formed only by a formation reaction. This observation is explained by the inflow of molten aluminum metal into the joint layer during the joint formation, a process which is central in the formation of a sound joint. Furthermore, bonding between different composites in the joint is achieved by lattice defects at their interface. Analysis of shear tests show that fracture occurs in regions at the metal base/joint interface where Al 2 O 3 particles were segregated. It is concluded that appropriate reactant design plays a significant role in controlling the microstructure, and thus, the bonding properties of the joint.