Predicting microstructure evolution for friction stir extrusion using a cellular automaton method

Abstract

Friction stir extrusion (FSE) offers a solid-phase synthesis method consolidating discrete metal chips or powders into bulk material form. In this study, an FSE machine tool with a central hole is driven at high rotational speed into the metal chips contained in a chamber, mechanically stirs and consolidates the work material. The softened consolidated material is extruded through the center hole of the tool, during which material microstructure undergoes significant transformation due to the intensive thermomechanical loadings. Discontinuous dynamic recrystallization is found to have played as the primary mechanism for microstructure evolution of pure magnesium chips during the FSE process. The complex thermomechanical loading during the process drives the microstructure evolution. A three-dimensional finite element process model is developed using commercial software DEFORM 11.0 to predict the thermal field, mechanical deformation and material flow during the FSE process. Using the simulated thermomechanical loadings as input, a cellular automaton model is developed to simulate the dynamic evolution of the material grain microstructure. The predicted grain size is in good agreement with the experimentally measured grain size. This numerical study provides a powerful analysis tool to simulate the microstructure transformation for friction stir-based processes.

Microstructures and properties of copper matrix composite wires reinforced with Ti2SnC particles

“…As shown, at a constant rotation speed of 1000 rev min −1 , the amount of plastic strain and temperature in the surface areas was higher than in the central areas of the wire. Similar findings were reported in other studies [27][28][29][30]. Under influence of plastic strain and temperature during the FSBE process, the microstructure underwent a dynamic recrystallisation phenomenon.…”

Effects of Ti2SnC MAX Phase on Microstructure, Mechanical, Electrical, and Wear Properties of Stir‐Extruded Copper Matrix Composite

“…However, the hardness changes in the central and edge areas of the wire are more pronounced in the sample without the MAX phase. Although noticeable changes in grain size of these two areas are not observed in the samples and the distribution of MAX phase in these areas is almost the same, as reported by other sources, [27,31,32] during the extrusion process, the plastic strain is more significant in the edge regions of the wire than in the central regions. Moreover, the increase in the density of dislocations and residual stress in the edge regions can effectively increase the hardness in the edge regions of the wire compared to the central regions of the wire.…”

“…According to refs. [26,27], dynamic recrystallization conditions were created under the influence of heat and strain applied during the process, and this phenomenon led to the formation of a fine and equiaxed grain microstructure. There was no significant difference in the grain size of the near-surface and central regions of the wires.…”

Thermo-mechanical Analysis of Friction Stir Welding: A Review on Recent Advances

“…Meanwhile, the approaches [74][75][76][77][78] for implementing a more reasonable heat loss model to the back plate were also developed for better predicting the heating and the cooling rate during the FSW. Recently, more research effort is being taken to predict the microstructure and the weld properties based on the thermo-mechanical analysis [73,79,80]. In the CSM-based analysis proposed by Miles et al [73], both the welding tool and the backing plate were considered explicitly in order to obtain a reliable temperature distribution, especially the heating and cooling rates, as shown in Fig.…”