The effects of Cr particles addition on the aging behavior and mechanical properties of SiCp/7075Al composites

The effects of Cr particles addition on the aging behavior and mechanical properties of SiCp/7075Al composites were systematically investigated. The results show that the precipitation sequence of (5 vol% Cr + 50 vol% SiC)/7075Al composites (C-7075Al) is still: GP zone -> eta' -> eta (MgZn2), but Cr particles degrade the precipitation kinetics of the C-7075Al composite in comparison to (5 vol% SiCp + 50 vol% SiCp)/7075Al (B-7075Al) because of reduced dislocation density present in the matrix and higher thermal activation energy of the eta' phase. Besides, the addition of Cr particles has a significant effect on the mechanical properties of the C-7075Al composite during the aging process. In contrast to the as-cast state, the ultimate tensile strength of the C-7075Al composite obtains an increase of 120 MPa at the peak-aged period, significantly lower than those of 7075Al alloy (207 MPa) and the B-7075Al composite (151 MPa), which is attributable to the severe aggregation of elemental Mg at the interface between Cr particles and the Al matrix.