Revealing the formation, strengthening and toughening mechanism of a new (Ti3AlC2+Al2O3)p /Al3Ti composite with strength-ductility synergy

Abstract

A novel (Ti3AlC2+Al2O3)p/Al3Ti composite was fabricated by vacuum hot pressing TiC, TiO2 and pure Al powders. Its phase formation and microstructure evolution were systematically investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscope (TEM) and a scanning electron microscope (SEM) with an energy-dispersive spectrometer system (EDS). The mechanical properties of the (Ti3AlC2+Al2O3)p/Al3Ti composite were measured using compression test and nanoindentation test. The results show that Ti3AlC2 is mainly grown from the intact TiC grains through epitaxial nucleation mechanism, while Al2O3 is precipitated via dissolution-precipitation mechanism. The measured mechanical properties show that the hardness of the Al3Ti alloy increases from 6.2 GPa to 8.79 GPa, and the strength of the composite has an increase of ∼15% while having a higher ductility. The enhancement of mechanical properties is attributed to the load transfer strengthening, which is related to the refinement of Al3Ti grains, the CTE mismatch between the Al3Ti matrix and the reinforcements, and dislocation multiplication caused by the precipitated Al2O3 particles in the Al3Ti matrix.