INFLUENCE OF MICROSTRUCTURE OF ALLOY 718 ON HIGH STRAIN RATE DEFORMATION

摘要

There are a number of situations where alloys for aero engines undergo deformation with high strain rates, e.g. during metal cutting. To understand, model and predict the behaviour we need knowledge of high strain rate behaviour, but also understand the influence of the microstructures. The material investigated is Alloy 718, a precipitate heat treatable nickel base alloy, heat treated to generate four microstructures; small and large grain size, aged and solution treated condition. Split Hopkinson was used for high strain rate compression testing; the strain rates tested in tensile and compression ranges 0.001-3000 s~(-1). To describe the deformation, the Johnson Cook material model was optimized for each microstructure. Present microstructure is influencing the stress response more than the strain rate and the different microstructures deform in slightly different manner where small grains tend to deform in primary glide and large grains deform in both primary and secondary glide systems.