Arcam AB fka AMAVF

[charlie T colton]

Location specific solidification microstructure control in EBM of Ti-6Al-4V

It sounds like these people have found a way to control localized microstructure in a way that can be performed by machine operators with the basic Arcam Level 1 traning. No PhD required.

The results confirm that the prior beta grain width scales with the effective melt pool width in bulk builds. This greatly simplifies the strategy for controlling the beta grain widths to one of controlling the melt pool size. These results were further used to vary the microstructure methodically in different locations in a single solid part. Further, this integrated melt pool dimension and microstructure control strategy was demonstrated to be achievable by modifying the Arcam-defined control variables that are accessible to any user with the basic (Level 1) operational training. Part qualification is critical for the widespread commercialization of AM and knowledge of the as-built properties is critical for speeding up the qualification process. This study contributes toward understanding and controlling the as-built microstructure in the Arcam EBM process space, which in turn governs the mechanical properties of the as-built part.

At sciencedirect.com -Location specific solidification microstructure control in electron beam melting of Ti-6Al-4V

Microstructure generally controls the mechanical properties of a material. AM microstructures differ from those formed in cast, rolled and other traditional manufacturing methods due to rapid solidification and resulting higher cooling rates. This difference in microstructure results in a difference in part properties [3]. Therefore, there has been great interest in studying AM microstructures and their associated mechanical properties [4–8]. These studies range from understanding the evolution of microstructure to changing the process conditions to control the microstructure and resulting mechanical properties in an additively manufactured part. Many of these studies focus on additively manufactured Ti64. Electron beam melted Ti64 consists of highly textured columnar prior beta grains which are aligned along the build direction and almost completely filled with a laths. Essentially all variants are present which results in a weak texture overall [9–11]. It is also reported that, for nominal build parameters, increasing the preheat temperature degrades the mechanical properties [9]. Microstructure and resulting properties have been observed to be affected by the energy density, part thickness/size, scanning pattern, build orientation, distance from the build plate, location on the build plate, and other process parameters [5,12–15]. Most of this prior research focuses on specific process variable combinations and part geometries. It lacks, however, a framework to quantitatively characterize the combined effects of processing conditions, part geometry and other factors on microstructure.

Using the process mapping approach [16,17], Bontha et al.[18,19] developed solidification maps that predict grain morphology in Ti64 in the Laser Engineered Net Shaping (LENS) process. Building on that, integrated melt pool geometry and microstructure control was demonstrated for Ti64 in both EBM and an electron beam wire feed process (EBF3) [20–22]. These studies focused on controlling prior beta grain size in single bead deposits of Ti64 via melt pool geometry control. This allowed for the prediction of microstructure for different process conditions in single bead geometries and these concepts were extended to solid parts [23]. This in turn opened up the opportunity for location specific control of microstructure in AM, which has not yet been explored in detail. Using the concept of prior beta grain width control in single bead geometries, this work explores variation of the grain width by controlling the melt pool geometry in solid test blocks and at multiple locations within a single part by methodically varying the primary beam parameters in the EBM process. To the knowledge of the authors, the current work is unique and it allows any EBM user with basic (Level 1) operator training on an Arcam machine to control prior beta grain widths in the raster regions of bulky as-built parts.