Mechanical response and damage evolution of bio-inspired B4C-reinforced 2024Al composites subjected to quasi-static and dynamic loadings

Abstract

Inspired by nacreous architecture, the 2024Al/20–50 vol% B4C composites with a lamellar-interpenetrated structure were successfully manufactured via freeze casting and pressure infiltration, and the quasi-static and dynamic characteristics were conducted at strain rates ranging from 0.001 to 3000 s−1. The strength of the composites enhanced as the strain rate increased up to 2000 s−1 since the strain rate hardening effect facilitated the accumulation of dislocations. At the strain rate of 3000 s−1, the adiabatic shear banding and its induced cracking were formed as the strengthening mechanisms were overcome by the thermal softening, which converted the dislocation structure from dislocation clusters to recrystallized grains, accompanied by a decrease in dislocation density, thereby degrading the compressive strength. A rigid network structure was formed in the composites with high particle content, and each particle had more inter-particle contact points, which made the strength of the composites increase with the increase of particle reinforcement content. This was also the reason why the strain rate sensitivity of the composites was considerably raised by introducing more particle reinforcement. However, increasing particle content heightened the composite susceptibility to strain localization and adiabatic shear damage, resulting in more brittleness of the 2024Al/50 vol% B4C composite at high strain rates. These findings could deepen the comprehension of the mechanical response and damage evolution of nacre-like composites exposed to extreme conditions and promote their applications.