Abstract
A study was carried out to determine the deform behavior in a polycrystalline Ni-based superalloy based on micropillar compression tests. Three different heat treatments of this alloy were evaluated by systematically controlling the cooling rate from the supersolvus solutioning step, in order to examine the effect of γ' microstructure on the CRSS (Critical Resolved Shear Stress). It is shown that the γ' precipitates have the marked effect on the deform behavior of micropillar, as the size of the secondary γ' in the general microstructure decreased, the CRSS were increased; SEM and TEM examination show that compressive deformation behavior of [110] oriented micropillars is dominated by dislocation plasticity. Cross slip is occurring in different slip planes, and exhibits away slip lines as well as stacking faults across γ/γ' microstructure. The γ' and carbides in this alloy effectively impeded the motion of dislocations and inhibit the strain burst behavior, caused by the running out of dislocations to the surface of micropillars,which leads to the sustained strain hardening the plastic deformation stage of micropillars.
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