One of the critical microstructural attributes affecting the properties of additively manufactured (AM) alloys, including titanium alloys, is the growth of large columnar grains along the build direction, often leading to a growth texture. While most of the work in the reported literature is focused on Ti-6Al-4V and other α/β Ti-base alloys, there are rather limited investigations on the grain growth and texture development in AM processed β-Ti alloys. The present study demonstrates the potential of engineering the size, morphology, and micro-texture of grains in AM processed β-Ti alloys, including two binary model systems, and the commercial Timetal 18 alloy. The addition of trace amounts of solute elements like boron, carbon, and silicon to these AM β-Ti alloys resulted in significant changes in the microstructure. Depending on the solute element added, a grain refinement of the order of 50-100 times was noted. The change in the grain size is attributed to a combined effect of constitutional supercooling, caused by the solute rejection from the growing β grains, and the growth restriction factor (Q) of the grains caused by the solute elements. The addition of these solute elements also changed the morphology of the grains from being columnar to more equiaxed; a much more pronounced change than observed in traditional α/β alloys such as Ti-6Al-4V. A change in texture of the β grains along the build direction was also noted; wherein the addition of solute elements randomized the texture from the typically observed strong (001)β oriented grains in AM Ti alloys.
- Understand the importance of the parameters for AM to control the microstructure and thus the mechanical behavior.
- Gain insight into understanding the role of solute elements in controlling and effecting the grain growth and texture evolution during the AM process.