Particle-induced dynamic recrystallization in adiabatic shear bands of B₄C/Al composites under ultra-high strain rates

Adiabatic shear band (ASB) formation is intrinsically difficult to initiate in Al-based materials, due to their high stacking fault energy and strong dynamic recovery. Here, dynamic shear experiments at ultra-high strain rates exceeding 10⁴ s⁻¹ were employed to trigger pronounced adiabatic shear localization in B₄C/Al composites. By integrating microstructure characterization with mesoscale SPH (Smoothed Particle Hydrodynamics) simulations, the deformation response, strain localization, and dynamic recrystallization (DRX) of the Al matrix were systematically investigated. Under ultra-high strain rate loading, the composites exhibit a distinct stress collapse followed by a quasi-steady plateau, reflecting the formation of ASB driven by DRX. Microstructural analyses reveal that severely elongated Al grains within the shear bands transform into ultrafine equiaxed DRX nanograins (<200 nm), accompanied by local strain energy accumulation. Simulations reveal that B₄C particles intensify strain localization through deformation incompatibility, leading to pronounced strain-rate amplification, increased local temperature rise (up to 276 K), and enhanced strain energy storage, thereby driving the Al matrix to reach the critical conditions for dynamic recrystallization within an extremely short loading duration. The particle-induced dynamic recrystallization provides a mechanistic basis for the design and reliability assessment of particle-reinforced composites subjected to ultra-high strain rate loading.