Strengthening behavior of AlN particles in different aluminum alloys

In order to investigate the strengthening effect and its mechanism of AlN particles in aluminum alloys with different strength levels, the microstructures of AlN particles reinforced 1070, 6061 and 2024 aluminum alloy based composites (V_f=40%) were observed before and after tension. The high density of dislocations generated by thermal misfit was found in both the matrix and AlN particles before tension. After tension, the dislocations in the matrix and AlN particles propagated at the same time. The testing results of mechanical properties show that among three composites fabricated with various aluminum alloys, the highest strengthening rate can be obtained in the 1070 pure aluminum with low strength and high plasticity, and high strength and plasticity can be obtained in the 6061 alloy with medium strength and relatively higher plasticity. This may be related to the fact that AlN particles yield some micro-deformation during tension and relax some internal stress near the interface. Due to the low plasticity, AlN_p/2024 composite tends to fracture at low stress and it is very difficult for AlN particles to give full scope to their strengthening effect.