Bulk nanocrystalline W-Ti alloys with exceptional mechanical properties and thermal stability

Nanocrystalline (NC) W metals and alloys often exhibit higher radiation tolerance and strength than their coarse-grained counterparts. However, their thermal stability is low, making it difficult to achieve bulk NC W metals and alloys by consolidation using conventional techniques such as pressure-less sintering, hot-explosive-compaction sintering, and spark plasma sintering. Here we report the synthesis and mechanical properties of bulk NC W100-xTix (x = 10 at.%-30 at.%) alloys prepared by consolidating mechanically alloyed NC powders under a high-temperature/high-pressure condition. Adding 20 at.%-30 at.% Ti largely improves the sinterability of NC W-Ti alloy powders. The room-temperature microhardness and compressive yield strength of consolidated bulk NC W80Ti20 alloy are similar to 16.9 and 6.0 GPa, respectively, which are mainly caused by grain boundary strengthening and significantly higher than those of previously reported W and W alloys. The ultimate compressive strength of bulk NC W80Ti20 measured between 900 and 1100 degrees C deceases with increasing temperature. This behavior can be explained by the activation of Rachinger grain boundary sliding. No grain growth is observed in bulk NC W80Ti20 after compression at 1000 degrees C. Theoretical calculation suggests that it is the segregation of Ti at grain boundaries that decreases the specific grain boundary free energy and makes the NC W80Ti20 alloy thermodynamically stable. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

Bulk nanocrystalline W-Ti alloys with improved sinterability and superior mechanical properties were synthesized under high-temperature/high-pressure conditions, showing enhanced grain boundary strengthening compared to conventional W alloys.