Intermetallics growth during annealing of three-layered light alloys platters manufactured by explosive welding

In the explosive welding (EXW) technique, classified as a solid-state process, connection is achieved by impelling the flyer plate towards the base plate using energy of explosion. The main advantage of this method is that an almost unlimited variety of metals can be successfully bonded in a single operation. Due to the appearance of the jet a self-cleaning phenomenon can be observed, in which contaminations and impurities are removed from the joined surface making the diffusion phenomena highly efficient. Although EXW goes under rapid conditions of high pressure and also locally temperature (far from the equilibrium state), often as a next step the annealing process is performed, where the diffusion governs the growth of intermetallic phases. Such a procedure can be applied for the development of multilayered materials composed of different metals with continuous intermetallic layers in-between them which thickness can be controlled. A composite obtained using this method can be applied as the ballistic multi-layer shield.

Two sets of light alloys: A1050/Ti gr. 2/A1050 and A1050/AZ31/A1050 were analyzed using scanning electron microscopy and synchrotron radiation measurements directly after EXW as well as after annealing in vacuum atmosphere at various temperatures (550°C, 630°C for A1050/Ti gr. 2/A1050 and 300°C, 350°C, 400°C for A1050/AZ31/A1050) for time periods (up to 100h).

Location of the interface with respect to the explosive material strongly determines its shape, chemical composition and phase evolution during further annealing. Differences between both interfaces were distinguished in aluminum-titanium samples in the state after EXW. Furthermore, they were also observed in aluminum-magnesium samples after heat treatment. The growth of the intermediate phases was governed by various mechanisms with respect to the annealing temperature and system of study.