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 °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 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 °C. More specially, 3 vol% 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 3 vol% to 4 vol%.