Dynamic shear properties of alloy 718 over wide temperature range

In this study, a split Hopkinson torsional bar was utilised to study the dynamic shear deformation behaviour of Alloy 718 at shear strain rates of 1000, 1500 and 3200 s ^-1 and temperatures of -150, 25 and 300°C. It was found that the mechanical behaviour of Alloy 718 is sensitive to both the strain rate and the temperature. The yield shear stress and work hardening coefficient increased with increasing strain rate, but decreased with increasing temperature. In addition, the fracture shear strain increased with increasing strain rate and temperature. The strain rate sensitivity and temperature sensitivity increased with increasing strain and strain rate, but decreased with increasing temperature. It was found that the high strain rate plastic deformation of Alloy 718 alloy can be adequately described using the Kobayashi and Dodd constitutive equation. Finally, the fracture surfaces were found to contain multiple dimple-like features. The dimple density increased with increasing strain rate and temperature. Thus, it was inferred that the ductility of Alloy 718 increases at higher strain rates and temperatures.