SUMMARY

Recent work has shown the capability of spherical nanoindentation to capture local structure-property relationships in natural materials and polycrystalline cubic metals by measuring indentation stiffness and yield strength from stress-strain curves as a function of the local microstructure in the indentation zone. However it is still very difficult to infer bulk structure-property relationships using these indentation protocols, which is mainly due to a lack of understanding indentation length scale effects and the important role played by various microscale interfaces (e.g., grain boundaries, phase boundaries). It is the goal of this work to extend these protocols to systematically study length scale effects of mechanical properties and their variance, while also identifying the precise role of interfaces on the selected properties. Two material systems, Ti-6Al-4V and a freeze-cast Ti-6Al-4V-PMMA composite will be studied using indentation experiments, finite element simulations, electron backscatter diffraction, and micro-computed tomography. Ti-6Al-4V selected for this study displays a rich variety of two phase microstructures, while the Ti-6Al-4V-PMMA composite is being critically explored for lightweighting structural applications. The proposed extension of the indentation protocols, together with its high throughput potential, will have a profound impact on speeding up the process of developing new structural materials by reducing the time and energy spent in mechanical characterization.