High strain rate deformation and resultant damage mechanisms in ultrafine-grained aluminum matrix composites

Ultrafine-grained aluminum composites produced via cryomilling exhibited ultrahigh strength associated with considerable strain-to-failure (>14 pct.) at high strain rates (>103 s−1), but only limited strain-to-failure (∼0.75 pct.) at quasi-static strain rates (10−3 s−1). The mechanisms leading to these differences in behavior were investigated by systematic microstructural analysis of deformed and pre-deformed samples. Micro-flaw developments, including kinking, extensive axial splitting, and grain growth, were observed after high strain rate deformation, and the significance of these mechanisms is considered.