Grain size evolution in pure iron: effects of build layout and preheating in PBF-EB manufacturing

Additive manufacturing (AM) relies particularly on the precise control of thermal paths to achieve desired microstructural and mechanical properties of the processed material. Complex geometrical shapes often associated with AM result in varying cross sections and consequently differing energy inputs, which can lead to localized variations in thermal history that influence material response. The present work explores the impact of different thermal histories during the AM process on the final properties of built components. In the present study the influence of scan area and preheat on the material properties is investigated. The number of specimens on the build plate was altered without changing the process parameters to examine how build plate affects overall process temperature and microstructure. Additionally, using the same build layout and melt parameters, the preheat step was varied to explore its impact on final microstructure. The results show that changes in the number of specimens significantly impact the energy input, build chamber temperature, grain size, and eventually strength. Although adjusting the preheat also led to changes, the effects were less pronounced. These findings highlight the importance of understanding and controlling thermal conditions in AM processes to ensure consistent material properties and prevent unexpected component failures.