脉冲电流对典型枢轨材料高应变率剪切行为的作用规律

Adiabatic shear bands (ASBs) are a critical mechanism for inducing damage under high strain-rate shear impact, whereas the mechanism of high-current-density-induced shear deformation of armature and rail materials remains unclear. This study employs a pulsed power source and an electromagnetic repulsion disk device to investigate the shear deformation characteristics of typical armature and rail materials under high strain rates (≥10⁴ s^–1) coupled with high current densities (≥10⁸ A/m²). The results show that the ASB formation energy barrier decreases in the following order: pure copper, oxygen-free copper, CuCrZr alloy, Al₂O₃ dispersion-strengthened copper alloy, brass, and 7075 aluminum alloy. Therefore, 7075 aluminum alloy is the most prone to ASB formation, followed by brass, whereas other copper-based rail materials rarely exhibit ASB features. Both 7075 aluminum alloy and brass exhibit a current-induced suppression effect on crack propagation and ASB formation. Electron backscatter diffraction (EBSD) analysis reveals that numerous fine equiaxed grains are present within the shear bands of 7075 aluminum, and the texture within the bands significantly differs from that of the surrounding matrix. As current density increases, the grain size within the band increases, while the fraction of dynamically recrystallized grains decreases markedly. The formation of ultrafine grains and the texture evolution can be reasonably explained by mechanically assisted rotational dynamic recrystallization. The results indicate that thermal softening alone is insufficient to induce ASB formation; instead, softening caused by rotational dynamic recrystallization is the dominant mechanism. The current-induced temperature rise is calculated, and the yield strength decrease under high-strain-rate current loading is measured, based on which the width of adiabatic shear bands (ASBs) under current is determined. The theoretical predictions show that they are in good agreement with experimental results. The results indicate that the temperature rise and softening effect induced by pulsed current lead to an increase in ASB width, which intensifies energy dissipation, suppresses dynamic recrystallization, and inhibits the formation of adiabatic shear bands.