Development of adiabatic shearing bands in 7003-T4 aluminum alloy under high strain rate impacting

This study details an investigation about the formation and development of adiabatic shearing bands (ASB) in 7003-T4 aluminum alloy under high strain rate impacting. The influence of the strain and strain rate on the evolution of the ASB were investigated through dynamic impact tests performed on a split Hopkinson pressure bar (SHPB) system. The results show that, during high strain rate impacting, the local temperature rising of the sample, which results in the thermal softening overcomes the strain rate hardening and strain hardening, is the key factor for the formation of ASB. The threshold of the strain rate and strain for the formation of the ASB is 1353 s−1 and 0.17 respectively. The microstructure of the ASB is mainly comprised of elongated grains and incomplete dislocation cells. As the strain increased further, the temperature of the ASB exceeded the recrystallization temperature. It caused the microstructure of the ASB changed into equiaxed recrystallization grains, when the strain rate and strain was increased to 2535 s−1 and 0.32 respectively. This study also reveals that the strain is an important parameter for the shape development of the ASB. When impacted with strain rate of 2535 s−1, the ASB appeared as the strain reached 0.17 with an appearance of straight line in the 45° direction of the samples. As the strain further increased upon 0.28, it changed into a parabolic shearing band in shape.