Strong crack blunting by shear-coupled migration of grain boundaries in nanocrystalline materials

Micromechanics of fracturing in nanoceramics

“…reviews [1,2,4], book [3] and original papers [8][9][10][11][12][13]19]). These experimental data are logically explained within the concept that (i) conventional toughening micromechanisms (that dominate in microcrystalline-matrix ceramics) operate in specific, inherent to nanostructures, ways in nanocrystalline ceramics where they effectively hamper crack growth and (ii) new, special (inherent to nanocrystallinity) toughening micromechanisms come into play in nanocrystalline ceramics [30][31][32][33][34][35][36][37][38][39][40][41][42][43]. The new toughening micromechanisms are often related to specific deformation modes that operate in nanomaterials (e.g.…”

“…These micromechanisms typically involve plastic deformation processes mediated by grain and interphase boundaries [30][31][32][33][34][35][36][37][38][39][40][41][42][43]. Such interfacial deformation processes are dominant in nanocrystalline ceramics, for two reasons.…”

“…The specific toughening micromechanisms include the GB sliding [30], the stress-driven migration of GBs [36,43], the nanoscale twin deformation carried by partials emitted from GBs [31], the creep deformation conducted by GB processes (Ashby-Verall creep carried by GB sliding accommodated by GB diffusion and grain rotations [32,33]), the cooperative GB sliding and migration process [36,37], stress-driven GB rotations [39,41], slow and fast nanoscale rotational deformation modes [35,38,40].…”

A coupling crack blunting mechanism in nanocrystalline materials by nano-grain rotation and shear-coupled migration of grain boundaries

“…Investigations of the present authors have shown that the SCM mode can considerably enhance the intrinsic ductility [6], toughness [15], crack blunting [16] and dislocation emission [17] in NC materials. The coupled NGR-SCM process proposed by Li et al [11] has also been identified as an effective toughening mechanism in NC materials [14].…”

Strong Crack Blunting by Hierarchical Nanotwins in Ultrafine/Nano-grained Metals

“…This approximation should not affect the calculations significantly, as validated by our previous work. [34] The lengthy expressions of all the shear stresses that appear in Equations (1) and (2) are derived in the Supplementary Material (Section A).…”