There had been much recent interest in the possibility of combining grain size strengthening (Hall–Petch effect) with the transformation-induced plasticity effect (strengthening due to a martensitic transformation). The present work was concerned with the analysis of the combination of these two effects using a discrete dislocation–transformation model. The transformation-induced plasticity mechanism was studied for aggregates of grains of ferrite and austenite of different sizes. The discrete model permitted simulating the behavior at sub-grain length scales, capturing the complex interaction between pile-ups at grain boundaries and the evolution of the microstructure due to transformation. This indicated that, as the average grain size decreased, the relative strengthening due to the formation of martensite was significantly reduced and that the overall strengthening was mostly due to a Hall-Petch effect. This suggested that strengthening via transformation-induced plasticity was ineffective in fine-grained microstructures.

Analysis of Grain Size Effects on Transformation-Induced Plasticity Based on a Discrete Dislocation–Transformation Model. J.Shi, S.Turteltaub, E.Van der Giessen: Journal of the Mechanics and Physics of Solids, 2010, 58[11], 1863-78