Tuning hardness and fracture resistance of ZrN/Zr0.63Al0.37N nanoscale multilayers by stress-induced transformation toughening

Abstract

Structure and mechanical properties of nanoscale multilayers of ZrN/Zr 0.63 Al 0.37 N grown by reactive magnetron sputtering on MgO (0 0 1) substrates at a temperature of 700°C are investigated as a function of the Zr 0.63 Al 0.37 N layer thickness. The Zr 0.63 Al 0.37 N undergoes in situ chemical segregation into ZrN-rich and AlN-rich domains. The AlN-rich domains undergo transition from cubic to wurtzite crystal structure as a function of Zr 0.63 Al 0.37 N layer thickness. Such structural transformation allows systematic variation of hardness as well as fracture resistance of the films. A maximum fracture resistance is achieved for 2 nm thick Zr 0.63 Al 0.37 N layers where the AlN-rich domains are epitaxially stabilized in the metastable cubic phase. The metastable cubic-AlN phase undergoes stress-induced transformation to wurtzite-AlN when subjected to indentation, which results in the enhanced fracture resistance. A maximum hardness of 34 GPa is obtained for 10 nm thick Zr 0.63 Al 0.37 N layers where the wurtzite-AlN and cubic-ZrN rich domains form semi-coherent interfaces.

Strength, transformation toughening, and fracture dynamics of rocksalt-structure Ti1−xAlxNSangiovanni1, Tasnádi2, Johnson3 et al. 2020Phys. Rev. MaterialsSelf Cite

“…Similarly, plastic deformation along 111 faults in B1 refractory carbonitrides can be assisted by providing facile deformation paths: the energy barrier of {111}<1-10> slip is reduced by synchro-shear mechanisms in B1 Ti0.5W0.5N solid solutions and B1-TiN/B1-WNx superlattices due to the preference of B1 WN-rich domains to transform in more stable hexagonal WC-structures [72,73]. Analogous to the experimental findings for multilayer films of Yalamanchili et al [61] and Schlögl et al [62], in this work we show that alloying (in ideal defect-free structures) transition-metal nitrides with AlN canbeside spinodal age-hardening at elevated temperatures -enable B1→B4 transformation toughening mechanisms at 300 K, i.e., much lower than the typical brittle-to-ductile transition temperatures of refractory ceramics [29,31]. Table II.…”

Nitrogen-doped bcc-Cr films: Combining ceramic hardness with metallic toughness and conductivity

“…Transition-metal nitrides (TMN) such as CrN, fabricated primarily by sputter-deposition, represent a major research field in materials science 1,2,3,4,5,6 with more than 2000 publications in the past year alone. 7 Several papers 8,9,10 report a gradual increase in hardness H from bcc-Cr to β-Cr2N by a factor of 2.5 to 3.…”

Thermal and mechanical stability of wurtzite-ZrAlN/cubic-TiN and wurtzite-ZrAlN/cubic-ZrN multilayers

“…For example, when sandwiching ZrAlN and TiN during very high temperature (900 °C) growth conditions, the multilayer architecture allows for growth of c-AlN in a c-ZrN matrix in the ZrAlN sublayers where c-AlN further transforms to w-AlN when exposed to mechanical stress [28]. The transformation is associated with a volume expansion that promotes crack closure and yields an enhanced fracture toughness of the coatings [27,29].…”