Microstructure Dependence of Dynamic Impact Behaviour of ATI 718plus® Superalloy

ATI 718Plus®ATI 718Plus® is a γ′-strengthened nickel-based superalloyNickel-based superalloy developed to substitute the widely used Alloy 718Alloy 718 in aero-engine applicationsApplications. This newer superalloySuperalloy is a candidate materialMaterial for aero-engine turbine structures, with the requirement to withstand impact loading occurring at high strain rates during turbine blade out events. Furthermore, the understanding of the high strain rateStrain rate response of ATI 718Plus® is important in optimising its machinabilityMachinability during cuttingCutting operations. To predict and model the behaviour of ATI 718Plus® during these events and in other dynamic impact applicationsApplications, proper understanding of the high strain rateStrain rate behaviour of the alloy is important, but not presently available. Therefore, in this work, the influence of microstructural condition and strain rates on dynamic impact behaviour of ATI 718Plus®, using a modified version of direct impact Hopkinson bar, is investigated. It is observed that the age-hardened alloy exhibits a significantly reduced strain hardening and strain rateStrain rate hardening capabilities compared to the solution heat treated microstructureMicrostructure. Furthermore, microstructural examination of the deformed samples shows that the formation of adiabatic shear bands, which usually serve as damage nucleation site, is substantially suppressed in the solution heat treated microstructureMicrostructure, while the aged microstructureMicrostructure exhibits high propensity to form localised shear bands.