High-speed nanoindentation mapping of additive manufactured titanium alloys for aerospace application

Titanium alloys and γ-TiAl intermetallics are widely used in additive manufacturing of aerospace engine components, but their complex microstructures and related micromechanical properties have not been fully explored. In this project, we employ high-speed nanoindentation mapping, electron probe microanalysis, and electron backscatter diffraction to characterize as-deposited and heat-treated Ti-6Al-2Zr-Mo-V and alloys. Our results show the correlations between mechanical contrasts (hardness and elastic modulus) and phase contrasts (α and β). The hardness and elastic modulus of the α and β phases are increased due to the element redistribution after annealing (Al diffuses from β to α; Mo and V diffuse from α to β). We also use a K-means clustering algorithm to analyze nanoindentation dataset and distinguish between α and β phases. In addition, we used the AM technique to fabricate a γ-TiAl/Ti2AlNb graded material by depositing γ-TiAl powder on a Ti2AlNb alloy substrate. High-resolution scanning electron microscope (SEM) and high-speed nanoindentation are employed to characterize the microstructure and mechanical properties of the transition zone from the Ti2AlNb substrate (disk) to the γ-TiAl alloy (blade). Our study provides a new methodology to give a better understanding of the microstructure-mechanical property relationship of additive manufactured multiphase alloys across length scales.