Rapid heating induced ultrahigh stability of nanograined copper

Abstract

Inherent thermal and mechanical instability of nanograined materials bottlenecks their processing and technological applications. In addition to the traditional stabilization strategy, which is based on alloying, grain boundary relaxation was recently found to be effective in stabilizing nanograined pure metals. Grain boundary relaxation can be induced by deforming very fine nanograins below a critical size, typically several tens of nanometers. Here, we found that rapid heating may trigger intensive boundary relaxation of pure Cu nanograins with sizes up to submicrometers, a length scale with notable instability in metals. The rapidly heated Cu nanograins remain stable at temperatures as high as 0.6 Tm (melting point), even higher than the recrystallization temperature of deformed coarse-grained Cu. The thermally induced grain boundary relaxation originating from the generation of high-density nanotwins offers an alternative approach to stabilizing nanostructured materials.

Thermal Stability of Nanocrystalline Gradient Inconel 718 Alloy

“…The emission of SFs and nanotwins in this study led to the formation of faceted grain boundaries. Similar grain boundaries with zig-zag configurations have been reported in nanostructured Cu with good thermal stability [57]. Generally, a given grain boundary has five crystallographic degrees of freedom (three for the misorientation of the crystallographic axes of one grain and two for the inclination of the boundary between the two adjacent grains) [58].…”

“…The non-CSL 9R structure was found to minimize the grain boundary energy by forming a body-centered-cubic structured grain boundary in the face-centered-cubic matrix [60,61]. Faceting has been observed at both micrometer and nanometer scales in several cases [57,62]. These faceted grain boundaries have low-energy states and, therefore, are more thermally stable than conventional grain boundaries according to Equation (1).…”

Grain boundary migration and deformation mechanism influenced by heterogeneous precipitate

“…5a. This finding agrees well with the results in recent experiments, in which the motion of partial dislocations is activated when the GB migration is inhibited [2,5,6,43]. 2) For the case with a = 90°, the interaction causes GB deformation, which partially releases the highly local strain and thus avoids the nucleation of partial dislocations.…”

Formation of Nanolaminated Structure with Enhanced Thermal Stability in Copper

“…The 10-nm Schwarz crystal in Cu is even stable against grain coarsening when close to the equilibrium melting point [ 24 ]. Although intensive boundary relaxation can be triggered by rapid heating [ 30 ], deformed grains of about 70 nm in size show the worst stability and grain coarsening occurs when annealed at temperature lower than 0.3 T m . However, the present NL structure with thickness equivalent to the most unstable grain size exhibits excellent thermal stability, with its T on is 180 K higher than that of its equiaxed NG counterpart ( Figure 4 ).…”