Grain Refinement Techniques in Additive Manufacturing of Titanium Alloys

The microstructural control of titanium alloys produced by additive manufacturing (AM) has become a central challenge in achieving components with isotropic mechanical properties and high performance. Owing to steep thermal gradients and rapid solidification rates in processes such as laser powder bed fusion and directed energy deposition, columnar grains tend to form, leading to pronounced anisotropy and reduced fatigue resistance. Grain refinement strategies aim to disrupt epitaxial growth and promote an equiaxed grain structure. Approaches include the design of novel peritectic alloy compositions that alter solidification pathways, the introduction of heterogeneous nucleation agents (such as ceramic particles or intermetallic whiskers), and the optimisation of process parameters to enhance constitutional undercooling and induce a columnar-to-equiaxed transition. These techniques have yielded titanium components with finer prior-β grains, reduced texture intensity and improved strength-ductility combinations, with clear implications for aerospace, biomedical implants and high-value industrial parts.

Research from Nature Portfolio

Recent studies have demonstrated that peritectic titanium alloys, specifically designed for the thermal conditions of layer-by-layer fabrication, can deviate from the traditional β→α orientation relationship. By exploiting a novel solidification and cooling path, the primary α phase forms without inheriting the strong crystallographic alignment of the parent β phase. This results in a more homogeneous, equiaxed microstructure and substantially reduced anisotropy after post-build heat treatment. The development of these alloys marks a shift from retrofitting conventional titanium grades to bespoke compositions optimised for additive processing, laying the groundwork for the next generation of high-performance AM titanium materials.

Grain Refinement Techniques in Additive Manufacturing of Titanium Alloys publication trend

The graph below shows the total number of articles in grain refinement techniques in additive manufacturing of titanium alloys across all publications each year (not limited to Nature Index journals).

Technical terms

Grain refinement: Reduction in the average size of crystalline grains within a metal to enhance mechanical properties.

Additive manufacturing (AM): A family of layer-by-layer fabrication techniques that build parts directly from digital designs.

Heterogeneous nucleation: Initiation of solidification on existing substrates or particles, lowering the energy barrier compared with homogeneous nucleation.

Constitutional undercooling: Local temperature depression ahead of the solidification front caused by solute build-up, which promotes new grain formation.

Columnar-to-equiaxed transition (CET): The change from elongated, directionally grown grains to roughly equiaxed grains during solidification, often induced by increased nucleation.

References

1. Peritectic titanium alloys for 3D printing. Nature Communications (2018).
2. Grain refinement of Ti6Al4V by incorporating in-situ TiB nanowhiskers in laser melting deposition. Journal of Materials Research and Technology (2023).
3. On the Role of ZrN Particles in the Microstructural Development in a Beta Titanium Alloy Processed by Laser Powder Bed Fusion. Micromachines (2024).
4. Effect of Lanthanum Oxide on the Microstructure and Properties of Ti-6Al-4V Alloy during CMT-Additive Manufacturing. Crystals (2023).