Layer-preheating process governs defect suppression, β′ precipitation, and specific energy absorption in electron-beam powder bed fused commercially pure titanium lattice structures

Commercially pure titanium (CP-Ti) lattice structures fabricated via electron-beam powder bed fusion (EB-PBF) are promising candidates for load-bearing biomedical implants. However, process-induced defects and the poorly understood effects of in-situ thermal evolution limit their mechanical reliability. The present study systematically examines the influence of repeated layer preheating (LP) cycles ( n ) on the microstructure, compressive deformation behavior, and specific energy absorption (SEA) of EB-PBF-processed CP-Ti lattice structures. Substrate temperature measurements confirm that increasing n progressively elevates the cumulative thermal exposure of the powder bed. At the process level, this cumulative exposure serves as an LP-controlled thermal descriptor that consistently correlates with suppression of lack-of-fusion (LoF) defects, moderate sharpening of the ⟨0001⟩α fiber texture, and the gradual formation of a grain boundary Fe-enriched β′ precipitate network along α-grain boundaries. Among these factors, LoF defect suppression and β′ precipitation primarily contribute to mechanical performance, while texture sharpening exerts a secondary influence. Quasi-static compression testing demonstrates a transition in deformation morphology from defect-mediated, shear-band-like collapse at n = 2 to progressive, layer-by-layer collapse at n ≥ 8, accompanied by monotonic increases in peak stress, elastic modulus, and SEA. The evolution of SEA occurs through two mechanistically distinct regimes: a defect-dominated regime ( n = 2–8) characterized by plateau extension via LoF suppression, and a microstructure- and precipitate-dominated regime ( n = 8–20) characterized by plateau elevation through β′ precipitation strengthening, with the crossover occurring at approximately n = 8–10. These findings suggest that the LP cycle can serve as an in-situ thermal control parameter in EB-PBF, offering a process-design strategy to simultaneously reduce defects and enhance microstructural strengthening in CP-Ti lattice structures for biomedical applications.