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The laser powder bed fusion (LPBF) was applied for near α and near β - Ti alloys to investigate microstructure evolution depending on scanning conditions and creep deformation behavior related with microstructure. The melting pool boundaries that are formed by cyclic heating due to cyclic scanning of the laser beam were clearly observed in the as-built state in both alloys. The crystallographic orientation of the β phase was random in near α -Ti alloys, while columnar microstructures with crystallographic lamellar-like microstructure, a near single crystal-like microstructure, and polycrystalline structures were observed under the specific scanning condition in near β -Ti alloys. The martensite transformation from the β to α phase occurred during rapid cooling during LPBF. The fine martensitic a phase was formed inside the melting pool. In near α Ti-Alloy, a fine α phase formed with decrease of energy density, VED, while in near β -Ti alloy, the opposite behavior was observed; that is, a fine α phase formed at higher VED.
The creep deformation mechanism is dislocation creep, which depends on mainly the microstructure in the molten pool rather than the grain size in both alloys. Creep lives of LPBFed near α -Ti alloy were between those of the forged sample with bimodal structure and with lamellar structure. It was also found that the Hot Isostatic Press is helpful for improving creep life by eliminating micro-defects. In near β -Ti alloy, the creep strain was larger at low stress in the LPBFed samples compared with the forged sample, but the creep life was slightly longer in the LPBFed samples than in the forged sample. In addition, a creep rupture surface was observed at the melt-pool boundary, suggesting that the α phase, which continuously forms on the melt-pool boundary in near β -Ti alloy, is the crack formation site.

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Keyword: Ti-6Al-4Nb-4Zr, Ti-6Al-2Sn-4Zr-6Mo, Laser powder bed fusion, Alpha formation, Creep strength, Volume energy density, Crystallographic orientation

Conference: 2026 Materials Research Society Spring Meeting & Exhibit (2026-04-26 - 2026-05-01)

Funding:

• JSPS JP21H05198 (Science for Creation of Super-Titanium by Super Thermal Field)

Manuscript type: Author's version (Submitted manuscript)

MDR DOI: https://doi.org/10.48505/nims.6289

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Updated at: 2026-05-13 11:42:27 +0900

Published on MDR: 2026-05-13 14:27:30 +0900