Synergistic co-segregation of carbon and titanium enhancing thermal stability and mechanical performance of nanocrystalline tungsten

Bulk nanocrystalline tungsten alloys demonstrate exceptional potential for advanced structural applications due to their superior radiation tolerance and high strength, but are often limited by microstructural instability and manufacturing challenges. In this study, a bulk nanocrystalline W-19.4 at%Ti-3 at%C [(W 80 Ti 20 )C 3 ] alloy with a mean grain size of 21 ± 4 nm was successfully synthesized via mechanical alloying and high-temperature high-pressure (HTHP) consolidation. The material exhibits an outstanding vickers hardness of 21.7 ± 0.5 GPa, representing a 28.4 % improvement over its W 80 Ti 20 counterpart. Remarkably, it maintains a hardness of 18.2 ± 0.2 GPa after prolonged annealing at 1100 °C for 50 h, with grain growth limited to 35 ± 7 nm. Carbon addition further promotes microstructural refinement, reducing the average grain size from 39 ± 9 nm to 21 ± 4 nm under identical processing conditions. The alloy also demonstrates significantly enhanced high-temperature compressive strength, reaching 1493 ± 108 MPa, 708 ± 61 MPa, and 494 ± 99 MPa at 900 °C, 1000 °C, and 1100 °C, respectively, corresponding to strength improvements of 57 %, 24 %, and 23 % compared to carbon-free NC W 80 Ti 20 . Theoretical and experimental analyses reveal that carbon doping increases grain boundary diffusion activation energy and suppresses boundary sliding, thereby enhancing high-temperature mechanical performance. The synergistic segregation of carbon and titanium at grain boundaries effectively reduces interfacial energy, contributing to the exceptional thermal stability observed. These findings provide valuable insights into the design and fabrication of high-performance nanocrystalline tungsten alloys for extreme environment applications.