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

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 degrees 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 degrees C. In particular, the optimum tensile properties are obtained in 4 vol% Ti2AlN/TiAl composite which shows the highest fracture strength of 670 MPa and fracture strain of 0.39% at room temperature and the highest yield strength of 552.4 MPa and ultimate tensile strength of 645.3 MPa at 800 degrees C. More specially, 3 vol % Ti2AlN/TiAl composite shows the highest elongation of 13.4% at 800 degrees 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 degrees 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 3 vol% to 4 vol%.