The Role of Grain Size on Neutron Irradiation Response of Nanocrystalline Copper

Abstract

The role of grain size on the developed microstructure and mechanical properties of neutron irradiated nanocrystalline copper was investigated by comparing the radiation response of material to the conventional micrograined counterpart. Nanocrystalline (nc) and micrograined (MG) copper samples were subjected to a range of neutron exposure levels from 0.0034 to 2 dpa. At all damage levels, the response of MG-copper was governed by radiation hardening manifested by an increase in strength with accompanying ductility loss. Conversely, the response of nc-copper to neutron irradiation exhibited a dependence on the damage level. At low damage levels, grain growth was the primary response, with radiation hardening and embrittlement becoming the dominant responses with increasing damage levels. Annealing experiments revealed that grain growth in nc-copper is composed of both thermally-activated and irradiation-induced components. Tensile tests revealed minimal change in the source hardening component of the yield stress in MG-copper, while the source hardening component was found to decrease with increasing radiation exposure in nc-copper.

Atomic-scale investigation of triple junction role on defects binding energetics and structural stability in α-Fe

“…Recent development of advanced materials such as nanoporous [6,7], nanocrystalline (NC) [8][9][10][11][12], and nanocomposite materials [13,14] show promise for use as structural materials in extreme environments [9,10]. However, the grand challenge with broader applicability of such nanostructured materials has been the stability of the non-equilibrium microstructure during processing and deformation [15][16][17][18][19]. This significant degradation in properties of nanostructured materials is in part due to an increase in the large volume fraction of GBs along with TJs, which lack long-range crystalline order leading to diffusional processes such as sliding and/or rotation [20].…”

“…Further, in nanostructured materials, such as NC metals, as the mean grain size decreases below 10 nm, the percent microstructure constituted by GBs and TJs increases and can be in excess of 50% [21,22]. Thus, due to the large volume fractions of non-equilibrium defects, NC metals exhibit altered physical responses to deformation, temperature, and radiation [15][16][17][18][19], i.e., the structural stability of NC materials is driven by GBs (planar defects), TJs (line defects), and their underlying structures [23,21]. Hence, a fundamental understanding of the relationship between the line/planar defect structures and the associated properties is highly relevant to develop stable, interface-dominant materials.…”

Thermal and Radiation Stability in Nanocrystalline Cu

“…While nanocrystalline materials appear very promising in terms of radiation damage tolerance under certain energetic conditions, they suffer from a lack of microstructural stability and they are highly susceptible to grain growth even at low homologous temperatures [ 29 , 49 ]. Irradiation-induced grain growth has been observed in many materials at temperatures as low as −223 °C [ 9 , 12 , 31 , 32 , 33 , 34 , 35 , 36 ], which represents a temperature at which thermally driven grain growth would not be expected. Table 1 summarizes published results for irradiation-induced grain growth in pure Cu.…”

“…As shown in Table 1 , most studied nanocrystalline materials are produced via thin-film deposition: sputter deposition [ 31 , 32 , 72 , 78 , 79 ], pulsed deposition [ 35 , 80 ], electrodeposition [ 34 , 40 ], or gas deposition [ 44 , 45 , 81 ]. Deposited thin films result in high chemical purity materials as they are produced under a clean environment and they typically present columnar grains [ 82 , 83 ].…”

“…As such, they are not thermodynamically stable and can lose their ability to tolerate damage during prolonged irradiation. Grain growth during irradiation has been observed in various materials even at low temperatures where no thermally induced grain growth would be expected [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. Further, at higher homologous temperatures this irradiation-induced grain growth couples with thermally driven grain growth.…”