Processing, Microstructure Evolution, and Heat Treatment Response of AA2024 and Its Metal Matrix Composites of In Situ TiB2 Dispersoids

Aluminum-based metal matrix composites (MMCs) have drawn considerable attention in aerospace applications due to their superior mechanical properties. In this study, stir-cast samples of the Al alloy AA2024 with 3% TiB2 in-situ MMC were made using a mixed salt method. Base alloy and MMC were heat treated to T352 and T852 conditions involving aging at 191 degrees C for varying times of 8, 12, 16, and 20 h. Comprehensive structure-property correlations of the base alloy and its MMC are studied. The mixed salt route leads to the formation of TiB2. However, Mg loss in MMC was confirmed in MMC, where Mg from the base alloy melt mixed with dross. In the hot-rolled condition, both base alloys and MMC have good workability as compared to the heat-treated condition. The conversion of sub-grains (with lower misorientation) to high-angle grains is found to be faster in MMC as compared to the base alloy from hot rolled to the T852 condition, indicating the role of TiB2 in MMC. Base alloy has shown rolling texture, whereas MMC showed texture towards randomization. Peak strength was observed in an aging cycle of 191 degrees C for 8 h for the base alloy, whereas it has not shown a significant change in strength for MMC with increasing aging time. The main reason why MMC isn't as strong or responsive to aging as base alloys is that it loses the solute element (Mg), which means that MMC doesn't have any Al2CuMg precipitate. Compensation of Mg (1.5 wt.%) demonstrated improvement in strength of as-rolled MMC.