Adiabatic shearing localisation in high strain rate deformation of Al-Sc alloy

Aluminium-scandium (Al-Sc) alloy is subjected to shear deformation at high strain rates ranging from 3.0×10⁵s^-1 to 6.2×10⁵s^-1 using a compressive-type split-Hopkinson pressure bar (SHPB). The effects of the strain rate on the shear stress, adiabatic shear band characteristics, and fracture features of the Al-Sc alloy are systematically examined. The results show that both the shear stress and the strain rate sensitivity increase with an increasing strain rate. In addition, it is shown that an adiabatic shear band is formed within the deformed specimens for all values of the strain rate. As the strain rate is increased, the width of the shear band decreases, but the microhardness increases. Moreover, the distortion angle and the magnitude of the local shear strain near the shear band both increase with an increasing strain rate. At a strain rate of 3.0×10⁵s^-1 the fracture surface is characterised by multiple transgranular clearage fractures. However, for strain rates greater than 4.4×10⁵s^-1 the fracture surface has a transgranular dimple-like characteristic, and thus it is inferred that the ductility of the Al-Sc alloy improves with an increasing strain rate.