Integrated modeling of microstructure-property-distortion relationship in friction stir additive manufacturing

A Monte Carlo model is established to simulate grain morphologies and combined with a precipitate evolution model to predict the mechanical properties of different zones in different layers of friction stir additive manufacturing (FSAM). Subsequently, a subregion model is established by considering the different mechanical properties at different locations to predict the residual states in FSAM. Results indicate that equiaxed grains are formed in the stirring zone and that the average grain size can be decreased by increasing the build height. The yield strengths in the stirring and heat-affected zones increase along the build direction and decrease with increasing temperature. The error between the predicted and experimental yield strengths is 3.3%. By considering changes in the mechanical properties in the stirring and heat-affected zones, the distortion error between the experimental test and numerical model can be reduced by 25% compared with that between the experimental test and the conventional model. The predicted residual stresses can be reduced by considering the strength reduction caused by the friction stirring effect. As the number of built layers increases, the maximum distortion in FSAM increases.