Effect of Nb on microstructure and mechanical properties of Ti-xNb-4Zr-8Sn alloys

Ti-xNb-4Zr-8Sn (x = 16, 20, 24, 28, 36 wt%) alloys were fabricated using vacuum arc furnace melting with subsequent hot rolling and solution treatment. Tensile tests were conducted to evaluate the mechanical properties of the Ti-xNb-4Zr-8Sn alloys. The microstructural and phase composition were examined using scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDX), X-ray diffraction (XRD), and transmission electron microscope (TEM). The results show that the Nb content strongly affects the microstructure and the mechanical properties of the Ti-xNb-4Zr-8Sn alloys. With the increase of Nb content, more beta phase occurs in the alloy due to the stabilizing effect of Nb, and the alloys evolve from alpha"+beta (Nb: 16, 20, 24 wt%) duplex-phase structure to a single beta (Nb: 28, 36 wt%) phase structure. The Young's modulus decreases first with the increase of Nb and then increases when the Nb content increases over 24 wt%. The Ti-24Nb-4Zr-8Sn alloy shows the minimum Young's modules of 45 GPa. The tensile strength (UTS) of the alloys decreases with the increase of Nb content. The effect of Nb content on the microstructure and the mechanical properties of the quaternary alloys are elucidated, and the affecting mechanism is discussed in this study.