Descriptors for mechanical strength and slip-induced crack-blunting in refractory ceramics D.G. Sangiovanni, 1* A. Kraych, 2 M. Mrovec, 2 J. Salamania, 1 M. Odén, 1 F. Tasnádi, 1 I.A. Abrikosov 1 1 Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE 58183 Linköping, Sweden 2 The Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum, D-44780 Bochum, Germany Understanding the competition between brittleness and plasticity in refractory ceramics is of importance for aiding design of hard materials with enhanced fracture resistance. We carry out ab initio and classical molecular dynamics (AIMD and CMD) investigations at temperatures between 300 and 1200 K to identify atomic-scale mechanisms responsible for brittle fracture vs slip-induced crack-blunting in Ti-N ceramics. AIMD simulations of single-crystal and notched TiN lattices (1100 atoms) subject to tensile and shear deformation serve to verify predictions of mechanical properties separately obtained by CMD. Benchmarked by AIMD results, CMD is thus confidently used to probe the mechanical response of “large” (40000 atoms) notched TiN and TiNx models under mode-I tension. Although crack growth occurs in most cases, CMD simulations reveal that typically-brittle TiN and TiNx ceramics can – for comparable rates of accumulation of tensile and shear stress around a flaw – prevent fracture via nucleation and emission of dislocations from the notch tip. Furthermore, we identify descriptors based on properties calculated for ideal single-crystals which reproduce trends in mechanical behavior of flawed lattices. Specifically: (i) the probability of notched ceramics to resist fracture via slip-induced plasticity exhibits linear relationship with ideal tensile-to-shear strength ratios (I plasticity slip ), (ii) at parity of I plasticity slip values, the effective strength (fracture stress) of defective systems ranks according to the tensile strength of corresponding single-crystal phases. The descriptors proposed in this work pave the way for high-throughput screening of ceramics that may combine high strength to superior fracture resistance at room and elevated temperature. *Corresponding author: [email protected]
Descriptors for mechanical strength and slip-induced crack-blunting in refractory ceramics
May 19, 2023
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