Simultaneously improved strength and ductility in aluminum matrix composite with heterogeneous structures under impact loadings

Heterostructured composites with the coexistence of hard and soft phases can achieve a superior strength-ductility synergy. However, the deformation and fracture mechanisms of these composites under impact loading has not been comprehensively understood. In this work, an in-situ TiB2/2024 Al composite was adopted to investigate the role of heterogeneous structures on the tensile mechanical responses at different strain rates and temperatures. Surprisingly, a simultaneously enhancement of strength and ductility was found in the composite under impact loading. To explore the underlying mechanisms responsible for the observed mechanical behavior, microstructural analyses were performed on the samples before and after deformation. Results reveal that the composite has obvious heterogeneous structure consist of particle-rich regions (regard as hard phase) and particle-lean regions (soft phase). The interaction between the two phases can affect the strain hardening behavior of the composites at different plastic deformation stages. Compared with the strain rate insensitive matrix, the particle-induced constraint makes the flow stress of the composite increases substantially with an increase in strain rate. Meanwhile, the tortuous crack propagation paths induced by the cooperation of hard and soft phases contribute to the improved ductility at high strain rates.