Analysis on the temperature-dependence of the flow stress in metallic thin films based on an exponential decay model

This paper presents improved description of flow stress in metallic thin films based on model-inspired phenomenological approach. In our previous approach, figures of merit functions were examined to study the temperature-dependence of yield stress and find model equations that may work especially well for the small volume materials in the moderate temperature ranges (2 < TM/T < 5). We have investigated the underlying assumptions behind each model to substantiate their physical correctness. We examined the parameters in each models using the frame of flow stress being dislocation—mediated, thermally activated, and obstacle-controlled process. Further development of our framework finds a simple but physically valid model that describes the flow stress of thin films with reasonable consistency. This model, based on the assumption of exponentially decaying flow stress with temperature, is found to be physically valid because it is proven to be a simplified form of well-established mechanical threshold stress (MTS) model.