Shear banding deformation in Cu/Ta nano-multilayers

Nanoscale Cu/Ta multilayers with individual layer thickness ranging from 3 to 70. nm were deformed under nanoindentation at room temperature. Shear bands can be observed only when individual layer thickness is reduced to 9. nm or below, indicating formation of shear bands in the Cu/Ta multilayers is layer thickness dependent. By observing the cross sectional transmission electron microscope images of the indentation fabricated through focused ion beam technique, shear banding deformation causing a unique layer-morphology with prevalent mismatched laminate structure has been reported for the first time. By capturing and analyzing a series of typical indentation-induced deformed microstructures, a new physical mechanism of shear banding behavior in metallic nano-multilayers is suggested.