Crystallographic texture control in electron beam additive manufacturing via conductive manipulation

Additive manufacturing processes supplement traditional material processing routes with unique capabilities which can have profound impacts on component production. Physical prototyping is accelerated and the fabrication of complex components, difficult or impossible to produce conventionally, is realized. Metals research is often focused on identifying process windows to avoid defects which thereby yield desirable properties. In electron beam melting fusion processes, however, precise spatial control of the heat source allows for detailed microstructure manipulation. Design is therefore extended to the microstructure scale offering greater overall flexibility towards engineering high performance components. In this work the role of geometry and beam path sequencing in a powder bed electron beam melting process is investigated. It is observed that by carefully engineering the melting sequence the morphology and texture at the mesoscale can be controlled. Solidification in the build direction, which usually prefers [001] directions, is tilted by control of the heat flux vector which yields large columnar crystals with a strong [011] build direction preference. This newly developed conduction control strategy is demonstrated for producing alternating mesoscale structures in bulk samples. Furthermore, a new scanning strategy is demonstrated which may be suitable for promoting a randomized crystallographic texture during the additive manufacturing process. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).