Evaluation of Hall-Petch Coefficient at Grain Boundaries of Fe-based Alloys by Nanoindentation Method

Abstract

Hall-Petch slopes for each grain boundary of Fe-based alloys were measured by nanoindentation tests. Pop-in phenomenon was observed in a load-displacement curve during nanoindentation near a grain boundary, associated with a slip transfer across the boundary. A critical stress at which pop-in phenomenon takes place and a distance between the grain boundary and the indentations satisfied the Hall-Petch relationship. The Hall-Petch slope depended on alloying element and its amount, which is closely related to a segregation of the element at grain boundaries. The slope also varied with the type of grain boundary. The combination of activated slip systems in neighboring grains strongly influenced the slope.