Microstructure and high-temperature mechanical properties of co-continuous (Ti3AlC2+ Al3Ti)/2024Al composite fabricated by pressureless infiltration

Ti3AlC2/2024Al composites with a co-continuous structure were successfully fabricated from 2024Al powders and Ti3AlC2 porous preforms (with porosity of 48%, 41% and 35%, respectively) by pressureless infiltration at 930 degrees C. Long-rod like Al3Ti was in situ formed due to reaction of Ti atoms de-intercalated from Ti3AlC2 and liquid 2024Al, which interpenetrated with Ti3AlC2 to form a new continuous framework. The mechanical properties in relationship with the initially different volume fractions of Ti3AlC2 and 2024Al at room temperature and high temperature were investigated. At room temperature, 59 vol%Ti3AlC2/2024Al has the best comprehensive mechanical properties, with the flexural strength of 510 MPa, compressive strength of 729 MPa, and compressive strain of 5.49%. Due to the co-continuous structure and the excellent high temperature of Al3Ti, all samples exhibit well mechanical properties at 300 degrees C. Among them, 52 vol%Ti3AlC2/2024Al has the best performance with the ultimate compressive strength of 532 MPa, which is only 18.7% lower than room temperature. And even at 400 degrees C,it still has an objective compression strength of 394 MPa due to the highest content of Al3Ti. In addition, after quenching from 400 degrees C to room temperature, the residual flexural strength of 52 vol%Ti3AlC2/ 2024Al can be reached to 450 MPa with the mere reduction rate of 7.4%. And no cracks are observed at the boundary of each phase, which means the good thermal shock resistance of the composites.