The hardness and modulus of molybdenum/aluminum oxide microlaminates as determined by nanoindentation

[摘要] The elastic modulus and hardness of 1.2 $mu$m thick films made of alternating and equal layers of sputter deposited Mo and Al$sb2$O$sb3$ were measured by a depth-sensing indentation apparatus which can test the properties of submicron volumes of material. Microlaminates with bilayer thicknesses ($lambda$) of 5, 20, 30, and 100 nm were prepared and tested.The moduli of the microlaminates were found to follow a rule-of-mixtures. No ;;supermodulus effect;; was observed. The hardness of the 100 nm microlaminate was observed to be almost twice as high as the hardness of either as-deposited Mo or Al$sb2$O$sb3$. This may be evidence of the ;;superstrength effect.;;A new method for determining the area of contact between an indenting diamond and the tested sample as a function of the plastic depth of indentation was established. An accurate area function is necessary for deriving mechanical properties from indentation data.

[发布机构] Rice University

[效力级别] Materials