1502 Micros tructure and Strength of Nanomultilayers Fabricated by Electrodeposition

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  • 1502 電気めっき法で作製したナノ多層膜の微視的構造と強度(OS15-1 ナノ・マイクロの視点からの変形と破壊の力学)


Mechanical properties and microstructure of Ni/Cu multilayered films have been investigated. The Ni/Cu multilayers were fabricated by electrodeposition technique. Thickness of individual Ni and Cu layers was set at h=20nm and 50nm, and total thickness of the multilayers was about 4μm. From electron diffraction patterns obtained by transmission electron microscope (TEM) observation, both the Ni and Cu layers were epitaxially grown during the electrodeposition. After being removed from a substrate, the Ni/Cu multilayered films were monotomcally strained to examine tensile strength. Prior to the tensile test, some multilayers were annealed. Ultimate tensile strength of the as-deposited multilayer of h=20nm was about 900MPa. After the annealing at 573K for 1 hour, the ultimate tensile strength of the 20nm multilayer increased up to 1GPa. However, the annealing at 773K significantly lowered tensile strength because disappearance of the multilayered microstructure. From the X-ray diffraction analysis of the as-deposited 20nm multilayer, the X-ray peaks from the Ni and Cu layers were unclear: both the layers had almost the same lattice constant. On the other hand, clear Ni and Cu peaks were detected at the annealed 20nm multilayer. It is thus probable that the increased strength in the annealed 20nm multilayer was caused by appearance of misfit dislocations which normally exist at an interface between the crystals having different lattice constants.


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