Scaling Effect of Intermetallic Compounds in Al-Cu Composites

Abstract

The scale effect of intermetallic compounds (IMCs) significantly impacts the mechanical behavior of composites. To explore this, a series of Al-Cu composites containing IMCs of varying scales were prepared, focusing on their strengthening mechanisms and failure behavior. Experimental results revealed that differences in thermal expansion coefficients generated strain gradients at the interfaces between the IMCs and the matrix. At the nanoscale, the strain gradient alleviates stress by facilitating the nucleation of fault networks, thereby limiting the mean free path of dislocation motion and surpassing the Hall-Petch limit. Additionally, nano-IMCs capture dislocations, activating the Orowan strengthening mechanism. As the size of the IMCs increases, micro-IMCs struggles to interact with dislocations to form dislocation loops, while the SFs generated by stress relief serve as mobile dislocation sources. This accelerates dislocation pile-up at phase boundaries, leading to stress concentration and failure. This work provides guidance for the structural and compositional design of metal matrix composites.

Keywords: Intermetallic compounds, Interface structure, Metal matrix composites, Dislocation mobility, Scaling effect