Nanotechnology enabled design of a structural material with extreme strength as well as thermal and electrical properties

M Rajagopalan and KA Darling and C Kale and SA Turnage and RK Koju and BC Hornbuckle and Y Mishin and KN Solanki, MATERIALS TODAY, 31, 10-20 (2019).

DOI: 10.1016/j.mattod.2019.09.024

The potential benefits of nanocrystalline (NC) alloys for use in various structural applications stem from their enhanced mechanical strengths. However, deformation-induced grain growth in NC materials reduces the strength and is a widely reported phenomenon occurring even at low- temperatures. Controlling such behavior is critical for the maturation of bulk nanocrystalline metals in various advanced engineering applications. Here, we disclose the mechanism by which grain boundary sliding and rotation are suppressed when a NC material is truly thermo- mechanically stabilized against grain growth. Unlike in any other known nanocrystalline metals, the absence of sliding and rotation during loading, at extreme temperatures, is related to short-circuit solute diffusion along the grain boundaries causing the formation of solute clusters and thus a significant change of the grain boundary structures. The departure of this unusual behavior from the well-established norm leads to a strong enhancement of many mutually exclusive properties, such as thermo-mechanical strength, creep resistance, and exceptionally high electrical/thermal conductivity. This work demonstrates that Cu- based nanocrystalline alloys can be used in applications where conventional Cu-based polycrystalline materials are not viable.

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