The response of room temperature and high temperature tensile properties to the microstructure variation of an AlN + Si3N4/Al composite by heat treatment

An Al matrix composite reinforced by 7.7% nano-AlN and 5% submicron-Si3N4 particles has been fabricated, and the solution treatment (T4 treatment) at 540 °C was used to regulate the microstructure of the composite. The tensile properties at both room temperature and high temperature (350 °C) were emphatically analyzed in order to investigate the response of tensile properties to the microstructure variation of the composite. The results indicate that the matrix of the as-extruded composite undergoes recrystallization and grain growth after T4 treatment, resulting in the evolution of texture, grain boundary misorientation and dislocation density. Correspondingly, the tensile properties first increase and then decrease with treatment time. After solution treated at 540 °C for 180 min, the ultimate tensile strength and elongation at room temperature reach up to the peak values of 420 MPa and 17%, and the strength at high temperture is also up to 143 MPa. The mechanisms were discussed in detail. This work may be referred in designing new composites when concerning both room temperature and high temperture properties in the future.