Georgia Hilburn

The advent of additively manufactured (AM) titanium alloys offers increased design flexibility for structural engineering applications, particularly in the defense and aerospace sectors. However, material behavior under extreme conditions, such as high-velocity impacts, must be thoroughly understood before predictive modeling can enable accurate design. With respect to titanium alloys, unique microstructures and phase compositions affect how high-strain-rate deformation influences shock energy dissipation and spall failure, limiting predictive capability. In my research in the High Strain Rate Lab at Georgia Tech, I investigate the effects of mesoscale structure and phase stability on shockwave propagation, stress-induced phase transformations, and spall failure mechanisms in both wrought and AM Ti-5Mo-5Cr-5V-3Al alloy (Ti-5553).

Focusing on β-stabilized Ti-5553 as a promising alternative to α+β Ti-6Al-4V (Ti-64) for lightweight structural applications, my research investigates how the previously reported β→α'' martensitic phase transformation modulates shock parameters, including rise time, peak pressure, and spall strength, under varying grain orientations and archetypal microstructures induced by post-processing heat treatments. These heat treatments affect not only grain structure and orientation, but also phase fraction and overall phase stability. The key objective of this research is not only to connect microstructure to phase stability under high-stress conditions, but also to determine whether phase transformations promote or suppress spall through wave dispersion or microstructural alterations, while assessing the impact of heat treatment on high-strain-rate behavior.

In our approach, we use planar-impact gas-gun testing and time-resolved interferometry to induce shock loading and diagnose nanosecond-scale events and behaviors within our materials of interest. Pre- and post-mortem microstructural characterization via SEM, EBSD, EDS, and X-ray computed tomography (XCT), as well as computational simulations using the CTH code for wave-profile prediction, are used to correlate velocimetry data and shock-dissipative mechanisms with spall damage evolution.

In the future, I seek to leverage this research to further develop predictive models that associate AM microstructure with spallation behavior at a given strain rate and Hugoniot pressure.