Elasto-plastic behaviour of thin metal films

Abstract

By extracting the variation of the plastic strain rate from measurements of the stress–strain curves of thin films of varying thickness, the large extent of the microdeformation stage was determined for tensile deformation of free-standing thin films, as well as for films on substrates deformed by cyclic heating. The stress varies dramatically with strain during this stage. It is demonstrated that this behaviour is common to most fine-grained polycrystals, and that the extent of the microdeformation stage is much larger than the conventional 0.2% proof strain, and depends both on the material as well as on the measurement technique. Therefore a careful analysis of this stage is essential in measuring the mechanical behaviour of these materials.