Structural evolution and mechanical properties of TiB₂ reinforced 2024Al composite stimulated by heat treatment

The microstructural evolution and mechanical properties of 3 wt% TiB_2p reinforced 2024Al (TiB_2p/2024Al) composite stimulated by T6 heat treatment are reported in this work. Morphological results showed that the initial TiB_2p/2024Al composite fabricated by laser-directed energy deposition (LDED) consists of fine equiaxed grains with well dispersed TiB₂ particles, in which nanoscale Al₂Cu(Mg) precipitates are dispersed in the Al matrix. After the T6 heat treatment, ultrafine Al₂CuMg precipitates and few AlCuMnFe (T) dispersoids were observed in the matrix and grain boundaries. The sample which was solution treated at 495 °C temperature showed a higher compression yield strength of about 371.3 MPa and hardness of about 145HV, whilst the sample treated at 505 °C solution temperature (ST) had a relatively low compression yield strength of 289.8 MPa and hardness of about 128 HV. The reason is deduced to originate from the existence of negative factors such as the formation of microvoids. Quantitative analysis unveiled that grain refinement and Orowan strengthening should contribute to the high strength of the annealed TiB_2p/2024Al composite.