Evolution of dislocation substructures in metals via high- strain- rate nanoindentation

Deformation at high strain rates often results in high stresses on many engineering materials, potentially leading to catastrophic failure without proper design. High- strain- rate mechanical testing is thus needed to improve the design of future structural materials for a wide range of applications. Although several high- strain- rate mechanical testing techniques have been developed to provide a fundamental understanding of material responses and microstructural evolution under high- strain- rate deformation conditions, these tests are often very time consuming and costly. In this work, we utilize a high- strain- rate nanoindentation testing technique and system in combination with transmission electron microscopy to reveal the deformation mechanisms and dislocation substructures that evolve in pure metals from low (10(-2) s(-1)) to very high indentation strain rates (10(4) s(-1)), using face- centered cubic aluminum and body- centered cubic molybdenum as model materials. The results help to establish the conditions under which micro- and macro- scale tests can be compared with validity and also provide a promising pathway that could lead to accelerated high- strain- rate testing at substantially reduced costs.