Change in Microstructure, Mechanical Strength and Corrosion Resistance of Ti-8Mo-xNi Alloys through Various Sintering Temperatures

Abstract

In this study, three different powders are mixed and used to produce Ti-8Mo-xNi alloys in three different proportions: Ti-8Mo-4Ni, Ti-8Mo-6Ni and Ti-8Mo-8Ni. The Ti-Mo-Ni alloys simultaneously undergo various vacuum sintering temperatures of 1125, 1150, 1175 and 1200℃, respectively. The experimental results show that the Ti-8Mo-8Ni alloys acquire a higher sintering density (98.9%) and hardness (52.1 HRC) after sintering at 1175℃ for 1 h. However, due to the grain growth and increased amount of nickel in the Ti-8Mo-8Ni alloys, the transverse rupture strength (TRS) shows an obvious decrease (as compared with Ti-8Mo-6Ni, the TRS value decreasing from 1177 to 685 MPa). Consequently, the suitable Ni content of the Ti-8Mo-6Ni alloys which proves advantageous to the TRS results from the uniform distribution of the TiNi intermetallic compound precipitates within the β matrix. The sintered Ti-8Mo-8Ni alloys also possess the lowest corrosion current (I_corr = 1.87 × 10⁻⁷ A·cm⁻²) and highest polarization resistance (56084 Ω·cm²) in 3.5 mass% NaCl solutions. This result confirms that sintered Ti-8Mo-8Ni alloys effectively improve corrosion resistance.