Abstract
Epitaxial TiN/Vo^NbojN superlattices with a 1.7% lattice mismatch between the layers were grown by reactive magnetron sputtering on MgO(OOl) substrates. Superlattice structure, crystalline perfection, composition modulation amplitudes, and coherency strains were studied using transmission electron microscopy and x-ray diffraction. Hardness H and elastic modulus were measured by nanoindentation. H increased rapidly with increasing A, peaking at H values —75% greater than rule-of-mixtures values at A — 6 nm, before decreasing slightly with further increases in A. A comparison with previously studied lattice-matched TiN/Vo.6Nbo.4N superlattices, which had nearly identical composition modulation amplitudes, showed a similar H variation, but a smaller H enhancement of =^50%. The results suggest that coherency strains, which were larger for the mismatched TiN/V0.3Nb0.7N superlattices, were responsible for the larger hardness enhancement. The results are discussed in terms of coherency strain theories developed for spinodally decomposed materials. Nanoindenter elastic modulus results showed no significant anomalies.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1456-1467 |
| Number of pages | 12 |
| Journal | Journal of Materials Research |
| Volume | 9 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jun 1994 |
Funding
The authors gratefully acknowledge the financial support of the National Science Foundation, Grant No. DMR 9120108. The financial support of the National Science Research Council (NFR) and the NUTEK/NFR Thin Film Consortium in Sweden are also acknowledged. The work at Los Alamos was supported in part by Department of Energy Contract W7405-ENG-36 through the LANL Center for Materials Science.
ASJC Scopus subject areas
- General Materials Science
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering