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

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 similar to 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 eta' precipitates distribute in grain interior, while several coarser it precipitates located at LAGB and HAGB with the orientation relationship of (0001)//(11(-)1) and [101(-)0](eta)//[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. (C) 2018 Elsevier B.V. All rights reserved.