Additive manufacturing of Ti-6Al-4V parts : from microstructural control to architectured materials

Researcher : Charlotte de FORMANOIR Diapositive18                         Additive manufacturing can produce three-dimensional objects of virtually any shape, from a digital model, by laying down successive layers of material. This “bottom-up” manufacturing technology stands in opposition with the more constraining “top-down” approach conventionally adopted in the machining of a part and based on the removal of material. Electron Beam Melting (EBM) is a recently commercialized powder bed additive manufacturing process for metal parts. Thin layers of metal powder are successively deposited on top of one another and melted by an electron beam to the exact geometry defined by the designer, until a complete part is produced. EBM is well suited for the production of complex Ti-6Al-4V parts, which can be used in the medical implant market as well as in the aerospace industry. Electron beam melted Ti-6Al-4V parts undergo a complex process, characterized by a succession of melting, rapid cooling, and partial re-melting of each layer, with many parameters being involved in the process. Therefore, in order to produce defect-free parts for critical applications in a reproducible way, a better understanding of the links between process parameters, microstructure of the material and resulting mechanical properties is required. Besides, evaluating the influence of post-EBM treatments is a key for understanding and eventually improving the mechanical properties of electron beam melted parts. Once a deeper comprehension of the process is acquired, a better control of the microstructure, up to a local scale in the material, could be achieved. This could be applied to the production of architectured materials. More specifically, the EBM technology could be used to build complex structures containing a functionally graded microstructure. In other words, such parts would combine geometric architecturation at a macroscopic scale, and local heterogeneity of the microstructure.   Ti-6Al-4V-1                 Ti-6Al-4V-2