The mechanical properties of intermetallic Ni_50-xTi₅₀Al_x alloys (x = 6,7,8,9)

High-strength, heat- and oxidation-resistant low density Ti-Ni-Al intermetallic alloys have recently attracted attention competing with some conventional high temperature structural superalloy such as Ni-based superalloy. In the present study, the mechanical properties of Ti-rich Ni_50-xTi₅₀Al_x (x = 6,7,8,9) alloys were examined by compression tests at room temperature and at high temperature from 400 °C to 800 °C. X-ray diffraction, scanning electron microscopy as well as microhardness tester were utilized to characterize the microstructure as well as the structural evolution with the increasing Al additions. The systematic analyses of the mechanical behavior were made according to compression test at different temperatures. A yield stress of 1800 MPa and more than 10% of compression strain were achieved at room temperature; and a yield stress of 400 MPa at 800 °C. It is suggested that controlling the shape, the volume percent and the distribution of second phases in the matrix is most important to obtain good mechanical properties in these alloys. The strengthening mechanism of aluminum addition on the mechanical properties was discussed systemically according to the microstructure evolution and solution hardening and precipitation hardening upon Al addition.