The local grain boundary curvature in a model Ni-based superalloy was measured experimentally using Dehoff s tangent count method. The results show that the curvature parameter, K, which relates the grain size to the mean boundary curvature, varies both with the volume fraction of the second-phase particles and the holding time during high-temperature annealing. The values of K obtained from the specimens with high particle volume fractions (up to 24% by volume) are much lower than those reported previously for pure or dilute alloy systems. In addition, K decreases gradually as a result of Zener's pinning when grain growth stagnates. Since the local boundary curvature constitutes the driving force for grain growth, these observations could help to explain grain growth phenomena in heavily pinned systems.
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