Multi-Scale Damage and Microstructure Evolution of 2024al Alloy Under Ramp Wave Loading

Abstract

Understanding the strain rate-dependent response of materials is essential for optimizing their design and predicting service life. In this study, both ramp wave loading (104-105 s−1) and square wave loading (106 s−1) were achieved by controlling the projectile structure in plate impact experiments. Transient spallation damage was analyzed using Molecular Dynamics (MD) simulations, with particular focus on spall strength, precipitation behavior, and damage evolution in 2024Al alloy under ramp wave loading. The results reveal that ramp loading mitigates thermal softening through gradual stress variation and reduces dislocation–atomic interactions due to its extended rise time. Compared with square wave loading, the continuous strain under ramp loading promotes vacancy generation, facilitating abnormal precipitation. These factors collectively contribute to enhanced spall strength. The spallation mechanism is dominated by dislocation–grain boundary interactions, with void nucleation and growth primarily occurring at grain boundaries. MD simulations further show that Shockley dislocations at damage fronts govern the plastic response. The formation of double spall surfaces is attributed to tensile stress concentrations generated by shock wave reflections at the initial spall plane. This work offers new insights into impact-induced damage mechanisms and demonstrates the effectiveness of MD in capturing dynamic microstructural evolution under extreme conditions.

Keywords: Ramp wave, precipitation, Spall strength, Damage evolution, MD simulation