Achieving simultaneous enhancement of strength and ductility in Al matrix composites by employing the synergetic strengthening effect of micro- and nano-SiCps

The incorporation of micro- and nano-sized SiC particles (micro- & nano-SiCps) into Al matrix constituted the micro- & nano-SiCp/Al composites through powder metallurgy. A unique ultrafine-grained (UFG) microstructure with micro-SiCps distributed among Al grains and most of nano-SiCps dispersed in grain interiors is characterized. Based on this, the synergetic constraint of dual-scale reinforcements on deformation of Al matrix is employed to enhance dislocation accumulation through increased SiCp/Al interface area and Orowan pinning effect, resulting in an improved strain hardening capacity. Compared with 10 vol% micro-SiCp/Al composites, the composites with 1 vol% nano-SiCps and 9 vol% micro-SiCps exhibit notable tensile properties of 285 MPa in yield strength, 374.7 MPa in ultimate strength and 11.3% in total elongation, increased by 32.6%, 28.7% and 37.8%, respectively, while remain a comparable Young's modulus of 94.6 GPa. Theoretical analysis proves that the dominant strengthening mechanism in micro- & nano-SiCp/Al composites is dislocation strengthening, different from the load transfer in individual micro-SiCp/Al composites. Our work provides inspirations for fabricating high-modulus Al matrix composites with simultaneously enhanced strength and ductility.