Offering a deformation processing route to metal additive manufacturing, additive friction stir deposition is able to produce fully-dense, ultrafine-grained alloys with wrought-like mechanical properties in the as-printed state. Compared to other solid-state metal additive manufacturing technologies, which only involve local deformation, here the plastic deformation is global: the entire feed material undergoes severe plastic deformation at elevated temperatures. This leads to dynamic recrystallization during printing, resulting in a relatively uniform and significantly refined microstructure. In this presentation, I will provide an overview of the process-microstructure linkages for several alloys in additive friction stir deposition, such as Al, Cu, Ti, and steel. We show that the contact state at the tool-material interface and the material intrinsic properties, such as stacking fault energy, govern the recrystallization type (i.e., continuous or discontinuous) and texture development. Ultrafine grained alloys with complex hierarchical microstructures can be printed by engineering the mesostructure of the feed material.