We reported an investigation of the influence of length scale on stabilization of boron carbide (B4C) during plasma activated sintering. In the current work, AA7075/B4C powders containing two types of B4C particles (Micro-B4C and Nano-B4C) were cryomilled for 8 h in liquid nitrogen, respectively. The characterization of as-cryomilled powders indicated that both Micro-B4C particles and Nano-B4C particles could distribute homogeneously in the matrix. AA7075/Nano-B4C powder have a finer particle size and grain size relative to that of the AA7075/Micro-B4C powder. The influence of length scale on stabilization of B4C particles during plasma activated sintering was investigated in details. The statistical grain diameter analysis from transmission electron microscopy observation revealed that the grain size of AA7075/Nano-B4C bulk (similar to 77.4 nm) is finer relative to those of the AA7075 bulk (similar to 193.5 nm) and AA7075/Micro-B4C bulk (similar to 184.7 nm). The coupling effect of ex-situ Nano-B4C particles and in-situ dispersion particles contribute to the enhancement of the stabilization of the AA7075/Nano-B4C bulk. (C) 2018 Elsevier B.V. All rights reserved.