Programming Crystallographic Orientation in Additive-Manufactured Beta-Type Titanium Alloy.

Additive manufacturing processes often result in predictable crystallographic orientations in metallic materials. These orientations typically align with the build direction, such as <001> or <110>. Prior research has shown that such orientations influence mechanical properties like elastic modulus. However, a gap remains in the ability to program crystallographic orientation along arbitrary 3D directions. This uncertainty drives the need for new methods to control crystal growth during solidification. Existing approaches lack precision in tailoring orientations beyond the build axis. No prior work has resolved how to achieve this in biomedical alloys. The challenge is to develop a technique that allows for such control. This paper addresses that specific limitation in LPBF processes.

The aim of this study is to develop a method for programming crystallographic orientation in additive-manufactured materials along arbitrary 3D directions. The focus is on biomedical beta-type Ti-Nb-Zr-Ta alloys, which are known for their low elastic modulus. The motivation is to enable the customization of mechanical properties through controlled crystal growth. The study seeks to overcome the limitations of conventional directional solidification techniques. It also aims to demonstrate how this can be achieved using laser powder bed fusion. The goal is to establish a reproducible and generalizable method for orientation programming. This approach could expand the application of additive manufacturing in biomedical contexts. The study is driven by the need for precise material property control.

The study introduces a technique called multitrack coupled directional solidification (MTCDS). This method involves directional solidification of coupled multi-track melt pools. The process is guided by a specific temperature gradient direction. The technique is applied to beta-type Ti-Nb-Zr-Ta alloys using laser powder bed fusion. The orientation of the melt pools is carefully controlled to influence crystal growth. The β-Ti phase is observed to undergo continuous epitaxial growth. This results in the desired <001> orientation along arbitrary 3D directions. The method is tested and validated through material characterization and crystallographic analysis.

The MTCDS technique successfully programs the <001> crystallographic orientation along arbitrary 3D directions. This is achieved through controlled directional solidification of multi-track melt pools. The β-Ti phase exhibits continuous epitaxial growth under the specific temperature gradient. Elastic modulus values of approximately 60 ± 1.2 GPa are customized along the chosen direction. The method allows for precise orientation control in biomedical beta-type Ti alloys. The results demonstrate the feasibility of programming crystallographic orientation in 3D. The technique is shown to be effective in tailoring material properties. These findings suggest potential for broader application in additive manufacturing.

The authors propose that MTCDS is a viable method for programming crystallographic orientation in additive-manufactured materials. The technique allows for the customization of <001> orientation along arbitrary 3D directions. This is achieved through directional solidification of multi-track melt pools. The β-Ti phase undergoes continuous epitaxial growth as a result. Elastic modulus values are successfully tailored to approximately 60 ± 1.2 GPa. The method is demonstrated to be effective in biomedical beta-type Ti-Nb-Zr-Ta alloys. The authors suggest that MTCDS can be generalized to other metallic materials. The findings indicate potential for tailoring properties in a wide range of applications.