A pseudo thermo-mechanical model linking process parameters to microstructural evolution in multilayer additive friction stir deposition of magnesium alloy

Additive friction stir deposition has been proposed as a disruptive manufacturing process; involving com-plex thermo-mechanical mechanisms during multilayer material deposition. The current efforts have attempted to develop a FEM based pseudo-mechanical thermal model accounting for heat generation due to friction and plastic dissipation during multilayer additive friction stir deposition. The primary motivation for development of the model was to seek an understanding of thermo-mechanical mecha-nisms and their impact on microstructural evolution during additive friction stir deposition. The pre-dicted temperature-time profiles agreed well with the experimentally derived ones. The computational predictions indicate rise of the peak temperatures up to 0.8 times the melting temperature of Mg-alloy. In addition, the Zener-Holloman parameter, Ze evaluated using the computational model was correlated with the microstructural evolution during the deposition process. The unique thermo-mechanical processing conditions during additive friction stir deposition led to dynamic recrystallization followed by grain coarsening. A significant extent of texture strengthening was observed in the AFSD pro-cessed samples. The already established phenomenological relationship between Ze and grain size was used to predict the grain size in the present work. The computational predictions indicate that the recrys-tallized grain size ranged from 4 to 6 lm, and the post deformation grain coarsening varied in the range of 4-24 lm, thereby providing reasonable agreement with the experimental observations. (c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Additive friction stir deposition is a disruptive manufacturing process that allows for the deposition of multilayer materials. In this study, a finite element method-based pseudo-mechanical thermal model was developed to investigate the thermo-mechanical mechanisms and their impact on microstructural evolution. The computational predictions were in good agreement with the experimental observations, showing consistent temperature-time profiles and grain size changes.