Microstructure and Mechanical Properties of TiAl Matrix Composites Reinforced by Carbides

Abstract

TiAl alloys have the potential to become a new generation of high-temperature materials due to their lightweight and high-strength properties, while the brittleness at room temperature and microstructure stability at elevated temperature are the key problems. The preparation of composite materials is an effective way to solve these problems, because the mechanical properties of TiAl matrix composites can be improved by the close combination of the reinforced phase and matrix. The preparation methods, microstructure, and mechanical properties of TiAl matrix composites reinforced by carbides are reviewed from the literature in this paper. A comprehensive summary of the effect of C on TiAl alloys can reveal the relationship between the microstructure and mechanical properties and provide guidance for subsequent experimental works. Two forms of C in TiAl matrix composites are reviewed: solid solutions in matrix and carbide precipitations. For TiAl alloys, the minimum carbon content for the carbide precipitation is about 0.5 at.% for low-Nb-containing TiAl alloys and about 0.8 at.% for high-Nb-TiAl alloys. An appropriate amount of C can improve the tensile properties and flexural strength of TiAl alloys. The hardness of the composites is higher than that of pure TiAl due to solution strengthening when the carbon content is low. The minimum creep rate of TiAl alloys can be reduced by one order of magnitude by adding C at the amount near the solubility limit.