Abstract:

Friction stir additive manufacturing is a newly developed solid-state additive manufacturing technology. The material in the stirring zone can be re-stirred and reheated, and mechanical properties can be changed along the building direction. An integrated model is developed to investigate the internal relations of process, microstructure and mechanical properties. Moving heat source model is used to simulate the friction stir additive manufacturing process to obtain the temperature histories, which are used in the following microstructural simulations. Monte Carlo method is used for simulation of recrystallization and grain growth. Precipitate evolution model is used for calculation of precipitate size distributions. Mechanical property is then predicted. Experiments are used for validation of the predicted grains and hardness. Results indicate that the average grain sizes on different layers depend on the temperature in stirring and re-stirring processes. With the increase in building height, average grain size is decreased and hardness is increased. The increase in layer thickness can lead to temperature decrease in reheating and re-stirring processes and then lead to the decrease in average grain size and increase of hardness in stir zone.

Key words: Additive manufacturing, Friction stir welding, Integrated model, Precipitate, Re-stirring, Reheating