The effects of annealing phenomena on the energy absorption of roll-bonded Al–steel sheets during wedge tearing

The purpose of this paper is to investigate the effects of annealing phenomena on the energy absorption of Al–steel bilayer sheets, bonded by cold rolling, through wedge tearing. Tearing by wedge is a dissipating energy system that includes three components: cutting, friction and plastic deformation due to bending. In order to find the bonding and annealing effects on energy absorption, the non-bonded bilayer sheets are prepared in the same condition of bonded ones. The results show that energy absorption of bonded sheets is larger than that of non-bonded ones. This is due to different plastic bending moment of bonded and non-bonded bilayer sheets. Whenever the bond is improved by heat treatment, the energy absorption during tearing is increased, however the flow stress is decreased. The bonded sheets heat-treated at temperatures higher than 500 °C show the behavior such as non-bonded ones. SEM images from interfaces of layers and EDS analysis show formation of Al–Fe intermetallic phase at these temperatures leading to low bond strength.