Preparation, Microstructure, and Mechanical Properties of Nb4 AlC3- Nb5( Si, Al)3 Composites.

Niobium aluminum carbide ( Nb₄ AlC₃), as a member of the MAX phases, can retain its stiffness and strength up to over 1400°C, however, the strength at room temperature is relatively low. In this work, Nb₅( Si, Al)₃ was used to strengthen Nb₄ AlC₃. Nb₄ AlC₃- Nb₅( Si, Al)₃ composites with different amount of Nb₅( Si, Al)₃ were synthesized from the elemental powders by in situ hot-pressing/solid-liquid reaction synthesis process. The RT flexural strength was significantly improved from 370 MPa of monolithic Nb₄ AlC₃ to 432 MPa of Nb₄ AlC₃-15 vol% Nb₅( Si, Al)₃ composite without the degradation of its high-temperature mechanical properties. While a slightly decrease in fracture toughness occurs with the increment of Nb₅( Si, Al)₃ content. Meanwhile, Transmission electron microscopy ( TEM) observations reveal that the interfaces between Nb₄ AlC₃/ Nb₄ AlC₃, Nb₄ AlC₃/ Nb₅( Si, Al)₃, and Nb₅( Si, Al)₃/ Nb₅( Si, Al)₃ are free of amorphous layers, which is also beneficial to its high-temperature mechanical properties. [ABSTRACT FROM AUTHOR]