Grain Growth Kinetics of a Nickel-Based Superalloy Under Electric Pulse Treatment

Grain boundaries play a vital role in determining the mechanical and physical properties of metallic materials. Heat treatment (HT) is widely employed to modify the content and distribution of grain boundaries. However, achieving precise control by HT remains challenging due to the scale mismatch between heat transfer and microstructure evolution. Electric pulse treatment (EPT) offers a breakthrough in microstructure control, by unifying the scales of microstructure and heat generation through a local Joule heating effect, with significant acceleration to microstructure evolution through athermal effects. Those two aspects establish EPT as an effective approach to grain boundary regulation. Despite its advantages, the mechanisms underlying the thermal and athermal effects of EPT remain unclear. To this end, a study of the grain growth kinetics of a nickel-based superalloy with an inhomogeneous microstructure under EPT was carried out through experimental and theoretical approaches. Grain boundary migration behaviors in both coarse- and fine-grained regions were investigated, corresponding grain growth kinetics were established, and effects were validated via annealing twin evolution. The results reveal that EPT accelerates grain boundary migration more than HT, exhibiting a "target effect" where growth rates correlate with grain boundary density. The efficacy of EPT depends on the balance between enhanced grain boundary migration and a reduced treatment time.