Adiabatic shearing behaviour of unweldable Al–Sc alloy under extremely high shear loading

Abstract

The present study applies a compressive type split Hopkinson pressure bar to investigate the adiabatic shear behaviour of unweldable Al–Sc alloy under high strain rates ranging from 3·0 × 10⁵ to 6·3 × 10⁵ s^–1. The effects of the strain rate on the shear stress, adiabatic shear band characteristics, and fracture features of the unweldable Al–Sc alloy are systematically examined. The results show that both the shear stress and the strain rate sensitivity increase with increasing the 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 increasing the strain rate. At a strain rate of 3·0 × 10⁵ s^–1, the fracture surface is characterised by multiple transgranular clearage fractures. However, for strain rates greater than 4·5 × 10⁵ s^–1, the fracture surface has a transgranular dimple-like characteristic, and thus it is inferred that the ductility of the unweldable Al–Sc alloy improves with increasing the strain rate.