Surface film softening, which is associated with the generation of mobile dislocations at a film-substrate interface and their motion into the substrate, has been demonstrated previously for bcc metals and B2 ordered alloy substrates. MoSi2 exhibits features of limited dislocation mobility and plasticity similar to these materials and would also be expected to exhibit film-enhanced plasticity, but at much higher temperatures. In this investigation, 150 nm thick films of SiO2, MoSi2 and ZrO2 were deposited on MoSi2 substrates by electron beam deposition at ~50°C in an attempt to observe film softening. In initial experiments, hot hardness testing was utilized primarily to maintain deformation conditions characteristic of dislocation glide. ZrO2-coated MoSi2 demonstrates a large film-induced softening in hardness tests carried out at 0.5–1 kgf loads over the temperature range 25–1300°C.
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The portions of this research carried out at the University of Michigan were supported by the National Science Foundation, Grant No. DMR 9102414. Two of us (C.M. Czarnik and R. Gibala) acknowledge Department of Energy fellowship support which enabled us to do major portions of this research in the Center for Materials Science at Los Alamos National Laboratory.
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Czarnik, C.M., Gibala, R., Nastasi, M.A. et al. Surface Film Softening Effects in MoSi2. MRS Online Proceedings Library 288, 597–602 (1992). https://doi.org/10.1557/PROC-288-597