Wenjun Lu

TiAl alloys are attractive for lightweight high-temperature components, but their brittleness and poor printability strongly limit additive manufacturing. Here we develop electric-pulse-assisted selective laser melting to fabricate crack-free Ti-43.5Al-4Nb-1Mo-0.1B alloy with ultrafine α2/γ nanolamellae of~25 nm. The obtained alloy achieves a compressive strength of ~2.5 GPa with >10% plastic strain and retains a strength above 1.4 GPa at 750 ℃. Multiscale experiments and molecular dynamics simulations reveal that the dense α2/γ interfaces are not merely governs the strength enhancement, but active sites for interface-mediated plasticity. These interfaces promote stacking-fault emission in γ, enhance back-stress hardening, coordinate strain partitioning between α2 and γ, and suppress severe strain localization. At elevated temperature, the same interface-dominated mechanism limits extensive α2→γ transformation and delays widespread recrystallization, thereby stabilizing the nanolamellar structure. These findings demonstrate an effective route to interface-engineered TiAl alloys with simultaneous improvements in strength, plasticity, and high-temperature robustness.

Recent advancements in dislocation engineering are reshaping the traditional view towards ceramics being brittle. Here, we use KTaO ₃ (KTO), a perovskite oxide that is newly discovered with room-temperature bulk plasticity, and demonstrate that the seeded dislocations can effectively tune both mechanical and functional properties. We uncover a brittle-ductile-brittle (BDB) transition: low dislocation densities lead to brittle failure, intermediate densities (∼10 ¹⁴ m ⁻² ) enable superior compression plastic deformation capacity with strains over 20%, and high dislocation densities (∼10 ¹⁵ m ⁻² ) induce brittle fracture again. This dislocation density-dependent non-monotonic mechanical response challenges the traditional behavior of ceramics and offers design opportunities. Furthermore, dislocation densities can monotonically decrease thermal conductivity, revealing a tradeoff between mechanical strength and functionality. The findings reveal a critical threshold of dislocation density in optimizing the performance of functional oxides, and provide a framework for using dislocations to design advanced materials where mechanical durability and enhanced functionality are intertwined.