Preparation, Microstructure, and Mechanical Properties of Nb ₄ AlC ₃ – Nb ₅ ( Si , Al ) ₃ Composites

Abstract

Niobium aluminum carbide ( Nb 4 AlC 3 ), 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, Nb 5 ( Si , Al ) 3 was used to strengthen Nb 4 AlC 3 . Nb 4 AlC 3 – Nb 5 ( Si , Al ) 3 composites with different amount of Nb 5 ( 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 Nb 4 AlC 3 to 432 MPa of Nb 4 AlC 3 ‐15 vol% Nb 5 ( 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 Nb 5 ( Si , Al ) 3 content. Meanwhile, Transmission electron microscopy ( TEM ) observations reveal that the interfaces between Nb 4 AlC 3 / Nb 4 AlC 3 , Nb 4 AlC 3 / Nb 5 ( Si , Al ) 3 , and Nb 5 ( Si , Al ) 3 / Nb 5 ( Si , Al ) 3 are free of amorphous layers, which is also beneficial to its high‐temperature mechanical properties.