Investigation on particle strengthening effect in in-situ TiB2/2024 composite by nanoindentation test

Mechanical properties of in-situ 5.0 vol% TiB2 particle reinforced 2024-T4 alloy matrix composite (in-situ TiB2/2024-T4 composite) synthesized through exothermic reaction process are experimentally investigated using different approaches. Standard uniaxial tension tests are conducted, and SEM fractography is made to characterize the fracture mechanisms. The nanoindentation experiment and Oliver-Pharr method are employed to obtain the micro mechanical properties (indentation modulus and hardness). To carry out comparative study, all kinds of experiments have also been done for 2024-T4 alloy. The indentation results demonstrate that compared to 2024-T4 alloy, the dispersive in-situ TiB2 nano particles do not evidently alter the Young's modulus of Al matrix of the composite, but elevate the hardness of it by 33.7%, which further means that the increase of Young's modulus of this composite over the 2024-T4 alloy is mainly due to the high stiffness of TiB2 particle, and the increase of yield strength and ultimate strength of the composite can be attributed to microstructure strengthening to its Al matrix.