Nanotwinned CrN ceramics with enhanced plasticity

Ceramic materials are usually hard but brittle, and it is challenging to achieve a simultaneous enhancement of strength and plasticity using conventional strengthening methods. In ceramic materials with similar atomic size and properties, the fabrication of nanotwins is a promising approach to enhance the plasticity, but it is unknown whether the strategy works for transition metal nitrides. Herein, nanotwinned CrN (NT-CrN) with a twin density of 9.0 × 10¹⁵m^-2 and twin-containing grain volume fraction of about 52 % is prepared by adjusting the ion kinetic energy during growth. Owing to the twin boundaries, NT-CrN exhibits high hardness (>36 GPa) and enhanced room-temperature plasticity at the same time. Compression deformation of over 40% without brittle failure is achieved. The enhanced room-temperature plasticity is attributed to the distributions of nanotwin boundaries (nano-TB) which allow special slipping by twisting the polyhedron constructed by nano-TB without bond breakage. The accompanying twin proliferation and fusion subsequently dissipate the energy to enhance the plasticity.