Bulk nanocrystalline W-Ti alloys with exceptional mechanical properties and thermal stability. (1st July 2022)

• Record Type: Journal Article
• Authors: Xue, H.X.; Cai, X.C.; Sun, B.R.; Shen, X.; Du, C.C.; Wang, X.J.; Yang, T.T.; Xin, S.W.; Shen, T.D.
• Is Part Of: Journal of materials science & technology. Volume 114(2022)
• Page Start: 16
• Page End: 28
• Publication Date: 2022-07-01
• Subjects: Nanocrystalline -- W-Ti alloys -- Segregation -- Grain boundary energy -- Strength -- Hardness; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2021.11.015
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: Bulk nanocrystalline W-Ti alloys were prepared by high-pressure consolidation. Hardness and yield strength of bulk nanocrystalline W80 Ti20 are 16.9 and 6.0 GPa. High hardness and strength are mainly caused by grain boundary strengthening. Nanocrystalline W80 Ti20 is stable against high temperature and deformation. Segregation of Ti at grain boundaries makes nanocrystalline W80 Ti20 stable. Abstract: 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- x Ti x ( 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 W80 Ti20 alloy are ∼ 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 W80 Ti20 measured between 900 and 1100 °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 W80 Ti20 after compression at 1000 °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 W80 Ti20 alloy thermodynamically stable.