Development and strengthening mechanisms of a hybrid CNTs@SiCp/Mg-6Zn composite fabricated by a novel method

Abstract

The hybrid addition of CNTs was used to improve both the strengths and ductility of SiCp reinforced Mg matrix composites. A novel method was developed to simultaneously disperse SiCp and CNTs in Mg melt. Firstly, new CNTs@SiCp hybrid reinforcements were synthesized by CVD. Thus, CNTs were well pre-dispersed on the SiCp surfaces before they were added to Mg melt. Therefore, the following semisolid stirring and ultrasonic vibration dispersed the new hybrid reinforcements well in Mg-6Zn melt. The hybrid composite exhibits some unique features in microstructures. Although the distribution of SiCp was very uniform in the Mg-6Zn matrix, most CNTs distributed along the strips in the state of micro-clusters, in which CNTs were bonded very well with Mg matrix. Most of the CNTs kept their structure integrity during fabrication process. All these factors ensure that the hybrid composite have much higher strength and elongation than the mono SiC/Mg-6Zn composites. The dominant strengthening mechanism is the load transfer effect of CNTs. Apart from grain refinement, the CNTs toughen the composites by impeding the microcrack propagation inside the material. Thus, the hybrid CNTs@SiCp successfully realizes the reinforcing advantage of “1 + 1> 2”.