Room and high temperature mechanical properties of spray co-deposited SiCP/Al-Cu-Mg-Ag composite: Effect of pre-stretching

The effects of pre-stretching deformation prior to aging on the microstructures, precipitation behavior and mechanical properties of a spray co-deposited SiCP/Al-Cu-Mg-Ag composite were investigated. The results show that the composite exhibits uniform microstructure and fine grains of 2.4 mu m, and the interfacial products consisting of free Si and MgAl2O4 are beneficial to the interface bonding. The higher density dislocations at SiCP/ Al interfaces and grain boundaries induced by pre-stretching deformation disrupts the nucleation of Mg-Ag coclusters, thus suppressing the precipitation of Omega phase and promoting the precipitation of Cu-rich theta ' phase. The UTS of the pre-stretching and aging composites at ambient temperature keeps a level of 557.1 MPa due to the enhancement of dislocation strengthening and weakness of precipitation strengthening. At 350 degrees C, the small prestretching (2%) improves the high temperature mechanical properties with the YS, UTS and El of 168.9 MPa, 176.5 MPa and 5.9%, respectively. The improvement of mechanical properties of small pre-stretching (<2 %) specimen at elevated temperature is attributed to the precipitation of thermally stable a phases and the higher density dislocation. However, the high temperature mechanical properties decrease sharply when further increasing the extent of pre-stretching deformation (3 %).