Laser-Induced Solid-State Foaming of HIPed Ti6Al4V-ELI Alloy

Abstract:

The present work proposes a novel strategy that significantly shortens Solid-State Foaming (SSF) times, delivering a substantial improvement in process efficiency and paving the way for faster production of customized and functionalized prosthetic components. In particular, the evolution of porosity was evaluated in terms of both volume fraction and mean pore diameter and its subsequent effect on microhardness in a Ti6Al4V-ELI alloy that was initially densified via Hot Isostatic Pressing (HIP) and then subjected to Laser-Induced Solid-State Foaming (LISSF). This acronym was introduced by the authors to underline the originality of this approach, which is not reported in the existing literature. Localized heat treatments were performed using a CO₂ laser source at a target temperature of 1020°C, with three distinct dwell times (120, 240, and 360 seconds). To predict density variations and the resulting mechanical properties, two analytical models were implemented and validated: (i) the Johnson–Mehl–Avrami–Kolmogorov (JMAK) kinetic model, which effectively described the time-dependent evolution of porosity and pore growth under different thermal regimes (based on conduction phenomena vs. direct laser exposure) and (ii) the Ryshkewitch-Duckworth (RD) model, which was used to correlate the exponential decay of microhardness with increasing porosity. The experimental results and regression analyses confirm the high predictive accuracy of both models (R² greater than 0.95), demonstrating the feasibility of the LISSF process for fabricating titanium components with locally controlled porosity for biomedical applications with reference to the manufacturing of customized and functionalized prosthetic components, ensuring both structural reliability and enhanced performance. On the other side, experimental results demonstrated that process parameters play a critical role in the microstructural evolution: specifically, increasing the dwell time to 360 s under direct laser exposure (1020°C) led to a maximum porosity fraction of approximately 30% and a growth in mean pore diameter up to about 35 µm.

• Periodical: Solid State Phenomena (Volume 390)
• Pages: 39-50
• DOI: https://doi.org/10.4028/p-qK6j3v
• Online since: April 2026
• Authors: Pasquale Guglielmi*, Angela Cusanno, Antonio Piccininni, Emanuele Fulco, Donato Sorgente, Gianfranco Palumbo
• Keywords: Hot Isostatic Pressing, Laser-Induced Solid-State Foaming, Material Modeling, Porosity Evolution, Ti6Al4V-ELI Alloy

References

[1] Miko T, Petho D, Gergely G, et al. A Novel Process to Produce Ti Parts from Powder Metallurgy with Advanced Properties for Aeronautical Applications. Aerospace. 2023;10(4).

DOI: 10.3390/aerospace10040332

[2] Yang XL, Du XF, Xu ZL, et al. Progress in processing of porous titanium: a review. Rare Metals. Springer; 2024. p.1932–1955.

[3] Yadav MK, Yarlapati A, Aditya YN, et al. Processing and Development of Porous Titanium for Biomedical Applications: A Comprehensive Review. Journal of Manufacturing and Materials Processing [Internet]. 2025;9(12):401.

DOI: 10.3390/jmmp9120401

[4] Wu D, Li Y, Zhu W, et al. Fabrication and biocompatibility of a 3D-printed porous Ti-25Ta alloy scaffold. Discover Applied Sciences. 2025;7(7).

DOI: 10.1007/s42452-025-07367-6

[5] Tian JH, Li YH, Wu XJ. Research Progress on Biocompatible Sintered Porous Titanium Alloys for Hard Tissue Implants. Transactions of the Indian Institute of Metals. Springer; 2025.

DOI: 10.1007/s12666-025-03649-0

[6] Guglielmi P, Piccininni A, Cusanno A, et al. Manufacturing of a hybrid component in Ti6Al4V-ELI alloy by combining diffusion bonding and superplastic forming. Materials Research Proceedings. Association of American Publishers; 2023. p.37–44.

DOI: 10.21741/9781644902714-5

[7] Oppenheimer S, Dunand DC. Solid-state foaming of Ti-6A1-4V by creep or superplastic expansion of argon-filled pores. Acta Mater. 2010;58(13):4387–4397.

DOI: 10.1016/j.actamat.2010.04.034

[8] Murray NGD, Dunand DC. Effect of initial preform porosity on solid-state foaming of titanium. J Mater Res. 2006;21(5):1175–1188.

DOI: 10.1557/jmr.2006.0140

[9] Duckworth W. Discussion of Ryshkewitch Paper by Winston Duckworth. Journal of The American Ceramic Society-Ryshkewitch. Vol. 36, No. 2.

DOI: 10.1111/j.1151-2916.1953.tb12838.x

[10] Ryshkewitch E. Compression Strength of Porous Sintered Alumina and Zirconia. 1953.

[11] Fanfoni M, Tomellini M. The Johnson-Mehl- Avrami-Kohnogorov model: A brief review. Il Nuovo Cimento D [Internet]. 1998;20(7):1171–1182.

DOI: 10.1007/bf03185527

[12] Guglielmi P, Palumbo G. Production of porous titanium structures by combining hot isostatic pressing and solid-state foaming. CIRP J Manuf Sci Technol. 2024;52:58–72.

DOI: 10.1016/j.cirpj.2024.05.019

[13] Gibson LJ, Ashby MF. Cellular Solids: Structure and Properties [Internet]. 2nd ed. Cambridge Solid State Science Series. Cambridge: Cambridge University Press; 1997. Available from: https://www.cambridge.org/core/product/BC25789552BAA8E3CAD5E1D105612AB5.

[14] Lee MH, Kim KB, Han JH, et al. High strength porous Ti–6Al–4V foams synthesized by solid state powder processing. J Phys D Appl Phys [Internet]. 2008;41(10):105404.

DOI: 10.1088/0022-3727/41/10/105404

[15] Yu W, Zhou X, Kanj MY. Microfluidic Investigation of Foam Coarsening Dynamics in Porous Media at High-Pressure and High-Temperature Conditions. Langmuir. 2022;38(9):2895–2905.

DOI: 10.1021/acs.langmuir.1c03301

[16] de Freitas FE, da Silva RAL, Takahashi RJ, et al. Influence of Laser Remelting on Creep Resistance in Ti-6Al-4V Alloy with Thermal Barrier Coating. Coatings. 2025;15(2).

DOI: 10.3390/coatings15020220

[17] Cerri E, Ghio E. On Strain-Hardening Behavior and Ductility of Laser Powder Bed-Fused Ti6Al4V Alloy Heat-Treated above and below the β-Transus. Materials. 2024;17(14).

DOI: 10.3390/ma17143401