Microstructure and mechanical properties of Ti-21.5Nb alloy prepared by powder sintering used for internal combustion engine

The spark plasma sintering (SPS) technology was selected to prepare the Ti-21.5Nb-2Zr-1.2Mo-0.1Y titanium alloy materials (Ti-21.5Nb) used in internal combustion engine, and then the solid solution and aging treatments were operated. The microstructure, phase composition, and mechanical properties of the samples were investigated by scanning electron microscope, metallographic microscope, X-ray diffractometer, and universal tensile tester. The results show that the pre-alloyed spherical powders with high relative density are obtained by plasma rotating electrode method, and no holes are formed. The microstructures of both the sintered and the solid solution samples are composed of β phase and α phase. The Ti-21.5Nb alloys prepared by SPS and the conventional ingot alloys have the same change rule of phase structure. The sintered samples are composed of β isometric grain and α phase in a smaller size, and the particle size of β isometric grain is between 30 μm and 80 μm. After the solid solution treatment on the sintered samples at 800 ℃, the samples mainly consist of β phase, and the dispersive α phase in ellipsoid is also present in the β phase. After the solid solution treatment on the Ti-21.5Nb at 500 ℃, and the ω phase is precipitated in the alloys, while all the original α phase disappear. The solid solution treatment at 380 ℃, only α phase exist in the alloys, ω phase completely disappear. The Ti-21.5Nb alloys with the better mechanical properties can be obtained by solid solution treatment at 800 ℃.