Scaling effect of intermetallic compounds in Al-Cu composites

The scale effect of intermetallic compounds (IMCs) plays a pivotal role in governing the mechanical behavior of Al-Cu composites. To investigate this, a series of composites incorporating intermetallic compounds (IMCs) of varying dimensions was fabricated. Experimental results reveal that the mismatch in thermal expansion coefficients between the IMCs and the Al matrix induces interfacial strain gradients. At the nanoscale, these gradients facilitate the nucleation of fault networks that effectively impede dislocation motion by reducing the mean free path, thereby surpassing the limitations predicted by the conventional Hall–Petch relationship. Moreover, nanoscale IMCs serve as dislocation pinning sites, thereby activating the Orowan strengthening mechanism. In contrast, micron-scale IMCs demonstrate limited ability to form dislocation loops, and the stacking faults (SFs) generated during stress relaxation become sources of mobile dislocations. The acceleration of dislocation at phase boundaries leads to stress concentration and premature failure. These insights provide valuable guidance for the structural and compositional design of metal matrix composites .