Discovery of Guinier-Preston zone hardening in refractory nitride ceramics

Traditional age hardening mechanisms in refractory ceramics consist of precipitation of fine particles. These processes are vital for widespread wear-resistant coating applications. Here, we report novel Guinier-Preston zone hardening, previously only known to operate in soft light-metal alloys, taking place in refractory ceramics like multicomponent nitrides. The added superhardening, discovered in thin films of Ti-Al-W-N upon high temperature annealing, comes from the formation of atomic-plane-thick W disks populating {111} planes of the cubic matrix, as observed by atomically resolved high resolution scanning transmission electron microscopy and corroborated by ab initio calculations and molecular dynamics simulations. Guinier-Preston zone hardening concurrent with spinodal decomposition is projected to exist in a range of other ceramic solid solutions and thus provides a new approach for the development of advanced materials with outstanding mechanical properties and higher operational temperature range for the future demanding applications.
Funding: Swedish Research Council VR [2018-03957, 2021-03652, 2021-04426]; Swedish Energy Agency [51201-1]; Knut and Alice Wallenberg Foundation [KAW2019.0290, CTS 20:150]; Carl Tryggers Stiftelse [21:1272, 2017-00646_9]; Swedish Research Council VR-RFI [VR-2018-0597]; Swedish Foundation for Strategic Research [2021-00171]; Swedish Research Council [RIF21-0026]; Swedish National Infrastructure in Advanced Electron Microscopy [22-4, 2022-03071]; Aforsk Foundation; Competence Center Functional Nanoscale Materials (FunMat-II) VINNOVA; [KAW2016.0358]; [RIF14-0053]