Tensile properties and fracture behavior of in-situ synthesized Ti2AlN/Ti48Al2Cr2Nb composites at room and elevated temperatures

Abstract

Ti2AlN particle reinforced Ti48Al2Cr2Nb composites were prepared by in-situ reactive arc-melting method. The tensile properties and fracture behavior of the composites at room temperature and 800°C were investigated in comparison with those of the Ti48Al2Cr2Nb alloy. The results show that the microstructure of TiAl matrix is significantly refined due to the Ti2AlN particles which are distributed uniformly in the matrix. Compared with the unreinforced TiAl alloy, the tensile properties of the composites are enhanced both at room temperature and 800°C. In particular, the optimum tensile properties are obtained in 4vol% Ti2AlN/TiAl composite which shows the highest fracture strength of 670MPa and fracture strain of 0.39% at room temperature and the highest yield strength of 552.4MPa and ultimate tensile strength of 645.3MPa at 800°C. More specially, 3vol% Ti2AlN/TiAl composite shows the highest elongation of 13.4% at 800°C. The fracture surface analysis shows that the fracture mechanism of the composites is closely related to the deformation temperature and Ti2AlN content. The composites exhibit characteristics of cleavage fracture of the TiAl matrix and cracking of Ti2AlN particles at room temperature. While at 800°C, the fracture type of the composites changes from a mixed mode of brittle cleavage and ductile fracture to brittle fracture as the Ti2AlN content increases from 3vol% to 4vol%.