Toward improved damage-resistant materials

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Time evolution of spall-induced void formation in polycrystalline magnesium. Credit: Science Advances

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In Science Advances, a team of Los Alamos National Laboratory and University of California, San Diego researchers present new insights into the dynamic failure process in metals based on in situ, time-resolved, high-resolution measurements of early-stage void growth in ductile metals experiencing spall under shock loading.

Leveraging the unique X-ray energies and flux available at the Dynamic Compression Sector of the Advanced Photon Source at Argonne National Laboratory, the team used absorption contrast imaging to directly capture the time evolution of spall damage in metals at approximately1.6-micrometer spatial resolution. Their technique revealed a dependence of void distribution and size on time and microstructure — highlighting a divergence from the simplifying assumptions often made in predictive models.

Their data provide critical insights into a regime that has, up until now, been characterized by approximations — insights that can be used to validate and improve dynamic damage prediction models, which have the potential to lead to the design of superior damage-resistant materials.

Accurate modeling and predicting damage induced by dynamic loading is critical to designing superior damage-resistant materials. However, this has long proved difficult, given challenges in capturing the time-dependent evolution of void nucleation and growth in postmortem recovered samples and the need to make simplifying assumptions in analytical models because of the lack of this high-resolution, in situ, time-resolved experimental data.

While previous research has used proton radiography and X-ray diffraction to investigate time-resolved spallation in metals, these approaches are limited in key aspects such as achievable spatial resolution and direct measurement of void distribution, shape and growth. Phase contract imaging — used in this research — is a complementary technique providing fine spatial and temporal resolution, which is necessary to study early stages of void growth.

The team’s work, which relied on Los Alamos expertise in dynamic experiments and modeling, underscores the importance of high-resolution in situ measurements in obtaining a complete picture of material behavior during spallation. These new data propose to fill a gap in understanding of dynamic damage evolution and inform current void damage models, as well as lead to the development of new ones.

In particular, the work lays the foundation for the types of challenges that would be studied with a dynamic mesoscale materials science capability.

Funding and mission

This research, which was funded by the DOE and the Dynamic Materials Properties program, supports the Laboratory’s Nuclear Deterrence mission and its Materials for the Future capability pillar.

Reference

“In situ measurement of damage evolution in shocked magnesium as a function of microstructure,” Science Advances 9, 45 (2023); DOI: 10.1126/sciadv.adi2606. Authors: Brianna MacNider, Nicholas Boechler (University of California, San Diego); David Jones, Jesse Callanan, Matt Beason, George T. Gray III, Dana Dattelbaum, Saryu Fensin (Los Alamos National Laboratory)

Technical contact: Saryu Fensin (Materials Physics and Applications division)