Dynamic interactions of twinning, grain boundaries, and dislocation in deformed body-centered cubic iron under high strain rates

Understanding of dynamical responses and mechanical characteristics of metals and alloys at high strain rates holds significant importance in fundamental physics and optimizing the performance capabilities of materials. During high-speed impact scenarios, materials may be subjected to high pressure and plastic deformation, which have the potential to modulate their mechanical attributes. In this study, high-speed planar impact experiments were conducted to investigate the progressive alterations in the microstructures and mechanical properties in coarse-grain body-centered cubic (bcc) iron subjected to high-strain-rate (approximately 2.60-3.89 x 10(6) s(-1)) impact reaching approximately 15 GPa in a one-stage light-gas gun. The nanoindentation tests show that the nano-hardness of the post-shock iron improves 1.5 times from approximately 1.75-2.70 GPa. Microscopic analyses of the post-shock bcc-iron show no significant grain refinement but a noticeable increase in the twin boundaries (TBs) and low angle grain boundaries (LAGBs) proportion with increasing shock pressure. Therefore, the interaction between TBs, LAGBs, and dislocations in post-shock iron grains plays an important role in mediating its mechanical properties. Our findings serve as possible guidance for exploring the mechanical properties of single-crystalline and poly-crystalline iron-based materials, such as steel, with optimized mechanical performance. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(https://creativecommons.org/licenses/by/4.0/).