Interfacial segregation and precipitates behavior in the ultrafine grained Al-based metal matrix composites

Abstract

To provide insight into interfacial segregation and precipitates behavior in the ultrafine grained Al-based metal matrix composites, AA7075/B4C composite was selected as the model system. The bulk composite was synthesized via cryomilling, field assistant sintering and followed heat treatment. The segregation layer of MgO was observed to increase from ∼15 nm to 20–25 nm during heat treatment due to faster solute diffusion caused by the Al/B4C interface and large volume fraction of grain boundaries. In addition to the segregation, representative TEM results show that the spherical GP zone and platelet η′ precipitates distribute in grain interior, while several coarser η precipitates located at LAGB and HAGB with the orientation relationship of (0001)//(11(_)1) and [101(_)0]η//[110]Al. However, the precipitates at LAGB exhibit finer size relative to those at HAGB, which could be ascribed to the higher accumulation of solute atoms at HAGB to favor the growth and coarsening of the precipitation during heat treatment.