Monday  |  Executive CD  |  12:20 PM–12:40 PM

#19669, High-Throughput Investigation of Copper Spall Strength: Influence of Grain Size and Crystallographic Orientation

Spallation is a dynamic failure process that occurs under high strain rates, where intense tensile hydrostatic loading leads to internal failure within materials. In ductile metals, this failure process follows the stages of void nucleation, growth, and coalescence, which is strongly influenced by the material’s microstructure. Previous studies have indicated that the relationship between spall strength and grain size transitions from following a Hall-Petch relationship to an inverse Hall-Petch relationship as grain sizes vary from the nanometer to the micrometer scale. Based on atomistic calculations, this effect is expected to be more pronounced at higher strain rates above 10⁶/s. However, experimental evidence supporting such predictions, especially at nanocrystalline grain sizes, are sparse. In this study, an automated high-throughput Laser-driven Micro-flyer plate Impact (LMI) experimental system was utilized to investigate the spall strength of copper with grain sizes ranging from 10⁻⁹ to 10⁻⁵ m at the aforementioned strain rates. Copper polycrystals were prepared using a sputter coating methodology, and specimens were further annealed to grow grains to larger sizes. Additionally, the effect of crystallographic orientation in single-crystal copper was explored to define the experimental space and compare spall strength variations between polycrystalline and single-crystal copper. The material fabrication and experimental procedure were automated to accelerate the exploration process. This study provides a comprehensive experimental dataset on the spall strength of copper at extremely high strain rates and discusses the necessary methodologies to automate the spallation exploration process.

Piyush Wanchoo   Johns Hopkins University
Rohit Berlia   Johns Hopkins University
Tim Weihs   Johns Hopkins University
K.T. Ramesh   Johns Hopkins University